Japanese Crohn's Disease Patients Research Articles

HLA-DQA1*05 and upstream variants of PPARGC1B are associated with infliximab persistence in Japanese Crohn's disease patients.

Recently, the HLA-DQA1*05 (rs2097432) genetic variation has been reported to be linked to early infliximab (IFX) treatment failure in the Caucasian Crohn's disease (CD) population, but that evidence is scarce in the Asian population. This study aimed to investigate the relationship between rs2097432 and the cumulative discontinuation-free time of IFX (IFX persistence) in 189 Japanese biologics-naive CD patients. We also performed a genome-wide association study (GWAS) to discover novel genetic predictors for IFX persistence. The C allele of rs2097432 significantly increased the risk of early discontinuation of IFX [Hazard ratio (HR) = 2.23 and P-value = 0.026]. In GWAS, one locus tagged by rs73277969, located upstream of PPARGC1B which attenuates macrophage-mediated inflammation, reached genome-wide significance (HR = 6.04 and P-value = 7.93E-9). Pathway analysis suggested association of signaling by PDGF and FCGR activation signaling with IFX persistence (P-value = 8.56E-5 and 5.80E-4, respectively).

Factors contributing to the systemic clearance of infliximab with long-term administration in Japanese patients with Crohn's disease: Analysis using population pharmacokinetics .

Crohn's disease (CD) is a chronic inflammatory gastrointestinal disease with repeated cycles of exacerbation and remission. Infliximab (IFX), a chimeric anti-TNF-α monoclonal antibody, has been widely used for the treatment of CD. However, no study in Japanese CD patients receiving continuous IFX for more than 1year has been reported. To avoid therapeutic failure during long-term administration in Japanese CD patients, we evaluated the variable factors of IFX pharmacokinetics and the optimal trough IFX concentration at 8 weeks after administration. Population pharmacokinetic (PPK) analysis was performed using the nonlinear mixed-effect model based on the IFX serum concentration in 832 samples from 121 patients. A one-compartment model was used to examine interindividual variability in the systemic clearance (CL) of intravenously administered IFX. PPK estimates (estimated value, RSE%) were total clearance (CL: 0.018 L/h, 9.1) and volumes of distribution (Vd: 7.35 L, 12.0). Interindividual variability for CL and Vd of 0.11 and 0.16, respectively, was found. Body weight, antibody to IFX (ATI), and albumin level were factors affecting the IFX CL. IFX CL was greater in the ATI-positive than in the ATI-negative group. CL was also greater in nonremission patients. There was a significant association between the predicted serum IFX trough concentration at 8 weeks and therapeutic response with long-term continuous administration (p<0.05), with a higher concentration at 8 weeks seen in the remission group. Using these variables including body weight, ATI, and albumin level, the IFX dose could be calculated for individual CD patients to achieve the optimal therapeutic range.

FADS2 and ELOVL6 mutation frequencies in Japanese Crohn's disease patients.

Crohn's disease (CD) development is thought to involve genetic factors related to immune response as well as environmental factors, such as intestinal bacteria and diet, though no clear cause has yet been identified. In our previous study, we found that the concentrations of linoleic acid, stearic acid, and metabolites in erythrocytes differed between CD patients and healthy subjects. These factors related to lipid metabolism are controlled by Δ6 desaturase (fatty acid desaturase 2, FADS2) and elongase 6 (ELOVL6), respectively. In the present study, we analyzed the gene sequences of FADS2 and ELOVL6 in 52 Japanese CD patients, and then compared mutation frequencies with findings in healthy individuals. Nineteen FADS2 mutations and 33 ELOVL6 mutations were found. Furthermore, a new variant in the promoter region was shown in both genes, though no mutation in the coding region was found in either. For the FADS2 intron, the allele frequency of rs227784 (0.3365; 95% CI = 0.0337-0.01460) was higher than that in healthy subjects (0.0190). Furthermore, allele rs227784 had a greater association with CD (odds ratio = 4.4; 95% CI = 2.1-9.3). As compared with healthy Japanese healthy individuals, no mutations were found with a largely deviated allele frequency in the present CD group. However, the number of patients examined was small, thus the reliability of our results is limited. The present findings regarding genetic effects on CD onset and lipid metabolism may be weak.

Long-term prognosis of Japanese patients with biologic-naïve Crohn's disease treated with anti-tumor necrosis factor-α antibodies.

Background/AimsFew reports have described the long-term treatment outcomes of the anti-tumor necrosis factor-α antibody for Japanese Crohn’s disease (CD) patients. The aim of this study was to evaluate them and clarify the clinical factors that affect the long-term prognosis of the anti-tumor necrosis factor-α treatments.MethodsThis was a retrospective, observational, single-center cohort study. Japanese CD patients treated with either infliximab or adalimumab as a first-line therapy were analyzed. The cumulative retention rates of the biologics, relapse-free survival, and surgery-free survival were analyzed using Kaplan-Meier methods. The clinical factors associated with the long-term outcomes were estimated by both the log-rank test and Cox proportional hazard model.ResultsThe cumulative retention rate was significantly higher in the group with a concomitant elemental diet of ≥900 kcal/day, baseline C-reactive protein (CRP) levels <2.6 mg/dL, and baseline serum albumin levels ≥3.5 g/dL, respectively. The baseline serum albumin levels were also associated with both relapse-free and surgery-free survival. The lack of concomitant use of an elemental diet ≥900 kcal/day was identified as the only independent risk factor for the withdrawal of the biologics.ConclusionsBaseline CRP levels and serum albumin levels could affect the long-term outcomes in CD patients. Concomitant elemental diet of ≥900 kcal/day could have a positive influence on clinical treatment course.

Anorectal Cancer in Crohn's Disease Has a Poor Prognosis Due to its Advanced Stage and Aggressive Histological Features: a Systematic Literature Review of Japanese Patients.

Patients with Crohn's disease (CD) are generally known to be at an increased risk of cancer. The anorectal area is the most frequent cancer site in Japanese CD patients. However, the risks are not well defined. The aim of this study was to clarify the clinicopathological characteristics of Japanese CD-associated anorectal carcinoma patients and to explore screening methods for the detection of cancer at earlier stages. A systematic review of case series and reports of Japanese CD-associated anorectal cancer patients published between 1983 and 2016 was conducted. There were 144 cases of cancer arising from anorectal lesions of CD. The median duration from the onset of CD to the cancer diagnosis was approximately 17 (0-39) years. The most prevalent histological type of cancer was mucinous carcinoma (49.3%), and 82.1% of patients were over T3 invasion. There were only 15.6% cases with early stage disease. A total of 82% patients had enhanced symptoms, whereas 56.3% of the early cancer cases had no symptomatic changes. Approximately 90% of cases were diagnosed preoperatively, and almost all early cancer patients were diagnosed with colonoscopy. The 5-year overall survival rate was 35.8%. CD-associated anorectal carcinoma had a poor prognosis due to the advanced stage of the cases and aggressive histological features. As earlier-stage cancer is associated with a better prognosis than advanced stage disease, and it is also typically diagnosed by colonoscopy, surveillance colonoscopy may therefore help to improve the prognosis in cases without any symptomatic changes.

Factors predicting the therapeutic response to infliximab during maintenance therapy in Japanese patients with Crohn's disease.

Since anti-tumor necrosis factor (TNF)-α agents (TNF-α inhibitors) induce both clinical response and remission in patients with moderate to severe inflammatory bowel disease (IBD), the use of anti-TNF therapies has fundamentally changed the approach to treatment for patients with IBD. Infliximab (IFX) is a TNF-α inhibitor approved for the induction and remission of Crohn’s disease (CD). However, even among patients who initially demonstrate a clinical response to IFX therapy, secondary loss of response occurs, although the reason remains unknown. We therefore investigated predictive factors associated with the response to IFX in long-term maintenance treatment in Japanese CD patients. Eight types of single-nucleotide polymorphisms (SNPs) were investigated using the real-time PCR method, and patient characteristics were collected from the electronic medical records. The Crohn’s Disease Activity Index criteria were used as the response to IFX therapy. The observation period was 1 year after IFX had been administered for more than 1 year. Associations between the IFX response and patient characteristics were evaluated using the multivariate logistic regression model. We studied 121 unrelated adult Japanese with CD treated for more than 1 year with IFX as outpatients at Keio University Hospital from November 1, 2014 to November 30, 2015. Among them, 71 were classified as in remisson. In multivariate analysis, patients with the TNF-α 857C>T C/C genotype, shorter disease duration, without double dosing, and combination treatment with an immunomodulator had higher remisson rates than those with the C/T or T/T genotype, longer disease duration, with double dosing, and no combination treatment with an immunomodulator. The response to IFX in Japanese CD patients may therefore be predicted by these 4 characteristics in actual clinical practice.

LRRK2 but not ATG16L1 is associated with Paneth cell defect in Japanese Crohn's disease patients.

BACKGROUND. Morphological patterns of Paneth cells are a prognostic biomarker in Western Crohn's disease (CD) patients, and are associated with autophagy-associated ATG16L1 and NOD2 variants. We hypothesized that genetic determinants of Paneth cell phenotype in other ethnic CD cohorts are distinct but also involved in autophagy. METHODS. We performed a hypothesis-driven analysis of 56 single nucleotide polymorphisms (SNPs) associated with CD susceptibility or known to affect Paneth cell function in 110 Japanese CD patients who underwent ileal resection. We subsequently performed a genome-wide association analysis. Paneth cell phenotype was determined by defensin-5 immunofluorescence. Selected genotype-Paneth cell defect correlations were compared to a Western CD cohort (n = 164). RESULTS. The average percentage of abnormal Paneth cells in Japanese CD was similar to Western CD (P = 0.87), and abnormal Paneth cell phenotype was also associated with early recurrence (P = 0.013). In contrast to Western CD, ATG16L1 T300A was not associated with Paneth cell defect in Japanese CD (P = 0.20). Among the 56 selected SNPs, only LRRK2 M2397T showed significant association with Paneth cell defect (P = 3.62 × 10-4), whereas in the Western CD cohort it was not (P = 0.76). Pathway analysis of LRRK2 and other candidate genes with P less than 5 × 10-4 showed connections with known CD susceptibility genes and links to autophagy and TNF-α networks. CONCLUSIONS. We found dichotomous effects of ATG16L1 and LRRK2 on Paneth cell defect between Japanese and Western CD. Genes affecting Paneth cell phenotype in Japanese CD were also associated with autophagy. Paneth cell phenotype also predicted prognosis in Japanese CD. FUNDING. Helmsley Charitable Trust, Doris Duke Foundation (grant 2014103), Japan Society for the Promotion of Science (KAKENHI grants JP15H04805 and JP15K15284), Crohn's and Colitis Foundation grant 274415, NIH (grants 1R56DK095820, K01DK109081, and UL1 TR000448).

Increased expression of IL12B mRNA transcribed from the risk haplotype for Crohn's disease is a risk factor for disease relapse in Japanese patients.

IL12B is a promising candidate for a susceptibility gene in Crohn's disease (CD). The aim of this study was to perform a candidate gene analysis of IL12B in Japanese CD patients, investigate whether the genotype is associated with disease phenotypes, and determine how the risk allele affects susceptibility to CD. Three hundred seventy-five patients with CD, 265 patients with ulcerative colitis, and 463 healthy controls were examined. Ten single-nucleotide polymorphisms (SNPs) around IL12B were genotyped. Case-control and subphenotype (including disease course) analyses were performed. The allelic expression ratio of IL12B messenger RNA (mRNA) was examined by a SNaPshot analysis in lipopolysaccharide-stimulated monocytes. Four SNPs located upstream of the IL12B gene were significantly associated with CD. A conditional analysis revealed that these associations included two independent signals tagged by IL12B_1 and IL12B_3 (P=9.42×10-6 and 1.49×10-4 respectively). IL12B_3 was also associated with earlier relapse in CD (P=0.0144). The allelic expression ratios of IL12B mRNA transcribed from the risk haplotype to the protective haplotype tagged by IL12B_3 in lipopolysaccharide-stimulated monocytes from ten healthy controls heterozygous for IL12B_3 were significantly higher than that of the respective genomic DNA (P=0.00923). No SNP was associated with ulcerative colitis. We confirmed the association of SNPs located upstream of IL12B with CD in Japanese patients. The demonstrated allelic expression imbalance supports the idea that the IL12B risk haplotype confers susceptibility not only to CD onset but to also relapse through increased IL12B mRNA expression.

321 Paneth Cell Phenotype is Associated With Novel Genetic Determinants and Clinical Outcome in Japanese Crohn's Disease Patients

321 Paneth Cell Phenotype is Associated With Novel Genetic Determinants and Clinical Outcome in Japanese Crohn's Disease Patients

Su1406 Efficacy, Safety, and Demographics Factor of Adalimumab Therapy in 1693 Japanese Crohn's Disease Patients

Background: TNF alpha inhibitors are being increasingly used in IBD in women of fertile age. Studies to date have been mainly limited to case reports and case series with the largest observational cohort from 50 centres in the US. We aimed to prospectively assess the use of anti TNF treatment during pregnancy in a large European cohort. Methods: This was an observational cohort study addressing a 5 year period between 2008-2013. Female patients with IBD who had undergone anti-TNF treatment during pregnancy were identified using the IBD databases of 2 tertiary referral centres for IBD in Dublin. Patient characteristics including disease activity scores, duration, site and concomitant medications were recorded. Pregnancy outcomes including mode of delivery, miscarriage, ante and postnatal complications, age at conception and need for escalation of IBD treatment during pregnancy were also assessed. Neonatal outcomes including low birth weight, pre-term delivery, NICU stays or perinatal infection and timing of vaccines were also recorded. Data were analysed using t testing, contingency and logistic regression analyses. Results: From an IBD population of over 2,500 patients, 31 individual females who underwent anti -TNF treatment during pregnancy from 2008-2013 were identified with a total of 36 pregnancies. Median disease duration at time of pregnancy was 12 years (IQR 3-17). 85% had Crohn's Disease, 15% Ulcerative Colitis. Median Harvey Bradshaw Index pre-pregnancy was 4.5 (IQR 2-13). Median Mayo score was 1 (IQR 0-3). 57.3% received infliximab, 38% adalimumab, 4.7% certolizimab. 53.8% were on concomitant immunemodulators. The majority of patients stopped biologic treatment at the start of the third trimester. 67% had treatment reinstated in the postpartum period. Median age at conception was 30.5 (IQR 25-35). 19% had previous miscarriages. 92% had successful term pregnancies. 22% required escalation of treatment during pregnancy. 19.3% had a pregnancy complication including emergency section. 16% neonates had a low birth weight with 2 preterm deliveries and one case of NICU stay for meconium ileus. No perinatal infections were reported. 20%mothers breastfed. The majority of mothers delayed live vaccination of their children. Interestingly, there was a significant independent association between disease activity at time of conception and low birthweight (p < 0.01). There was no association between adverse outcomes or neonatal infections and anti-TNF use noted in this cohort.Conclusion: Disease control at time of conception and through pregnancy should be the main goal of treatment in this patient cohort and the use of TNF alpha antagonists to achieve this appears to warranted to improve pregnancy outcomes though definitive safety has yet to be proven.

Decreased abundance of Faecalibacterium prausnitzii in the gut microbiota of Crohn's disease

Dysbiosis is thought to be relevant to the etiology and pathogenesis of Crohn's disease (CD). In this study, we investigated the abundance of Faecalibacterium prausnitzii, as well as Bilophila wadsworthia, in the gut microbiota of Japanese CD patients. Forty-seven CD patients and 20 healthy controls were enrolled. Abundance of F. prausnitzii in fecal samples was quantified by real-time polymerase chain reaction. The gut microbiota profile was evaluated by terminal restriction fragment length polymorphisms. The abundance of F. prausnitzii significantly decreased in CD patients compared with healthy subjects. B. wadsworthia was scarcely detected in the same samples. Among CD patients, the Crohn's Disease Activity Index, C-reactive protein levels, and erythrocyte sedimentation rate were significantly lower, and serum albumin levels were significantly higher in the high F. prausnitzii group compared with the low group. Terminal restriction fragment length polymorphisms analysis showed that fecal bacterial communities of CD patients differed from those of healthy individuals. The changes in simulated bacterial composition indicated that class Clostridia, including genus Faecalibacterium, was significantly less abundant in CD patients as compared with healthy individuals. The bacterial diversity measured by the Shannon Diversity Index was significantly reduced in CD patients compared with healthy individuals. The decreased abundance of class Clostridia, including F. prausnitzii, may translate into a reduction of commensal bacteria-mediated, anti-inflammatory activities in the mucosa, which are relevant to the pathophysiology of CD. In contrast, the role of B. wadsworthia was suspected to be minimal.

FCGR3A-158 polymorphism influences the biological response to infliximab in Crohn’s disease through affecting the ADCC activity

An association between FCGR3A-158V/F polymorphism and biological responses to infliximab has been reported in Crohn's disease (CD) in Western countries. However, little is known about the mechanism by which gene polymorphism affects the responses to infliximab. The aims of this study were to confirm the association in Japanese CD patients and to reveal the effect of gene polymorphism on biological responses to infliximab. Japanese CD patients were examined retrospectively at weeks 8 and 30. Clinical and biological responses were assessed by the Crohn's disease activity index and C-reactive protein levels, respectively. The infliximab-binding affinity of natural killer (NK) cells from FCGR3A-158V/V, V/F and F/F donors was examined. Infliximab-mediated antibody-dependent cell-mediated cytotoxicity (ADCC) activities were also determined using transmembrane TNF-α-expressing Jurkat T cells as target cells and peripheral blood mononuclear cells (PBMCs) from V/V, V/F and F/F donors as effector cells. Biological responses at week 8 were statistically higher in V/V patients, whereas no significant differences were observed in either clinical responses at weeks 8 and 30 or biological responses at week 30 among the three genotypes. NK cells and PBMCs from V/V patients also showed higher infliximab-binding affinity and infliximab-mediated ADCC activity, respectively. Our results suggest that FCGR3A-158 polymorphism is a predicting factor of biological responses to infliximab in the early phases. FCGR3A-158 polymorphism was also found to affect the infliximab-binding affinity of NK cells and infliximab-mediated ADCC activity in vitro, suggesting that an effect on ADCC activity influences biological responses to infliximab in CD patients.

Clinical effects of adalimumab treatment with concomitant azathioprine in Japanese Crohn’s disease patients

To assess adalimumab's efficacy with concomitant azathioprine (AZA) for induction and maintenance of clinical remission in Japanese Crohn's disease (CD) patients. This retrospective, observational, single-center study enrolled 28 consecutive CD patients treated with adalimumab (ADA). Mean age and mean disease duration were 38.1 ± 11.8 years and 11.8 ± 10.1 years, respectively. The baseline mean Crohn's disease activity index (CDAI) and C-reactive protein were 177.8 ± 82.0 and 0.70 ± 0.83 mg/dL, respectively. Twelve of these patients also received a concomitant stable dose of AZA. ADA was subcutaneously administered: 160 mg at week 0, 80 mg at week 2, followed by 40 mg every other week. Clinical response and remission rates were assessed via CDAI and C-reactive protein for 24 wk. The mean CDAI at weeks 2, 4, 8, and 24 was 124.4, 120.2, 123.6, and 135.1, respectively. The CDAI was significantly decreased at weeks 2 and 4 with ADA and was significantly suppressed at 24 wk with ADA/AZA. Overall clinical remission rates at weeks 4 and 24 were 66.7% and 63.2%, respectively. Although no statistically significant difference in C-reactive protein was demonstrated, ADA with AZA resulted in a greater statistically significant improvement in CDAI at 24 wk, compared to ADA alone. Scheduled ADA with concomitant AZA may be more effective for clinical remission achievement at 24 wk in Japanese Crohn's disease patients.

Alendronate Improves Low Bone Mineral Density Induced by Steroid Therapy in Crohn's Disease

We investigated whether steroid therapy for Crohn's disease (CD) patients influences bone mineral density (BMD), and whether alendronate is effective for improving this loss of BMD. We recruited 16 outpatients with CD. The BMD of the whole body, the lumbar spine, and the proximal femoral neck was measured by dual-energy X-ray absorptimetry. The BMD was expressed as a T score. Some CD patients with low BMD values had been given vitamin K2 or alendronate for one year. In the steroid-dependent group, the mean dose of prednisolone was 968 mg per year and 2.7 mg per day. Although the duration of the disease was not related to the T score, the amount of total steroids was negatively correlated with the T score among patients taking no preventative drugs. The T score in the vitamin K2 group after one year did was not altered in the 3 areas examined. On the other hand, the T score in the alendronate group increased by 2.8% for the whole body, 4.5% in the lumbar spine, and 3.4% in the proximal femoral neck. The BMD of Japanese CD patients was decreased depending on the total amount of steroid administered, and oral alendronate improved the loss of BMD.

Association analysis of genetic variants in IL23R, ATG16L1 and 5p13.1 loci with Crohn’s disease in Japanese patients

Inflammatory bowel diseases, Crohn's disease (CD) and ulcerative colitis are characterised by chronic transmural, segmental and typically granulomatous inflammation of the gut. Each has a peak age of onset in the second to fourth decades of life and prevalence has been increasing significantly in both Western countries and Japan over the last decade, while their pathogenesis remains largely unknown. Recently, positive association of CD with the variants in interleukin 23 receptor (IL23R), autophagy-related 16-like 1 (ATG16L1) genes and chromosome 5p13.1 locus was reported through genome-wide association studies which are now recognised as a robust tool for the identification of susceptibility genes for complex diseases. To examine an association of reported susceptible variants in the three loci with Japanese CD patients, a total of 484 CD patients and 439 controls were genotyped. No evidence of positive association for any of these loci with CD was found in the Japanese population, even after clinically stratified subgroups of CD were used. Our result revealed a distinct ethnic difference of genetic background of CD that we reported previously in other genes between Japanese and Caucasian populations. Further genetic studies are required to confirm our findings with ethnically divergent populations.

Single nucleotide polymorphisms in TNFSF15 confer susceptibility to Crohn's disease

The inflammatory bowel diseases (IBDs), Crohn's disease (CD) and ulcerative colitis, are chronic inflammatory disorders of the digestive tract. The pathogenesis of IBD is complicated, and it is widely accepted that immunologic, environmental and genetic components contribute to its etiology. To identify genetic susceptibility factors in CD, we performed a genome-wide association study in Japanese patients and controls using nearly 80,000 gene-based single nucleotide polymorphism (SNP) markers and investigated the haplotype structure of the candidate locus in Japanese and European patients. We identified highly significant associations (P = 1.71 x 10(-14) with odds ratio of 2.17) of SNPs and haplotypes within the TNFSF15 (the gene encoding tumor necrosis factor superfamily, member 15) genes in Japanese CD patients. The association was confirmed in the study of two European IBD cohorts. Interestingly, a core TNFSF15 haplotype showing association with increased risk to the disease was common in the two ethnic groups. Our results suggest that the genetic variations in the TNFSF15 gene contribute to the susceptibility to IBD in the Japanese and European populations.

Nutritional therapy for Crohn's disease in Japan.

In Japan, nutritional therapy as both a primary and as a secondary treatment is widely used for Crohn's disease (CD). The rationale for its use is based on a variety of reasons. The first is its ability to induce remission and to ameliorate the activity of intestinal lesions in the short term by enteral (EN) or by parenteral nutritional therapy in which overexpressions of chemokine receptors in an active stage are decreased significantly in the remission stage. Second is its ability to maintain remission over the long term through home-based enteral nutrition in which tube feeding during the nighttime is encouraged. Third is its ability to reduce the steroid dosage over the period of a long-term treatment course. However, several disadvantages of this therapy such as unpalatability and sluggish effect have been pointed out. Several studies have attempted to resolve this issue and determine the best components of EN, especially in fat composition. Some data have been suggestive of too much long-chained fatty acid having a hazardous effect on EN's clinical efficacy because it works as a precursor of inflammatory prostaglandins. Our recent data show that medium-chained triglyceride did not have such a hazardous effect on clinical efficacy. Several studies suggested that the patient factors that were resistant to inducing remission in the short term were a long period of suffering CD, a high activity (on Crohn's Disease Activity Index, CDAI), hemorrhagic colitis, and colitis with marked cobblestoning. Japanese guidelines for the treatment of CD recommended nutritional therapy as a first-line therapy and as a maintenance therapy after inducing remission. This treatment policy has led to Japanese CD patients having lower mortality rates than that of patients who do not receive EN. If this therapy could be combined with other drug therapies, including strong immunosuppressants, treatment strategies would be improved over those we have at present.

Association analysis of SLC22A4, SLC22A5 and DLG5 in Japanese patients with Crohn disease

Crohn disease (CD) is an inflammatory bowel disease characterized by chronic transmural, segmental, and typically granulomatous inflammation of the gut. Recently, two novel candidate gene loci associated with CD, SLC22A4 and SLC22A5 on chromosome 5 known as IBD5 and DLG5 on chromosome 10, were identified through association analysis of Caucasian CD patients. We validated these candidate genes in Japanese patients with CD and found a weak but possible association with both SLC22A4 (P=0.028) and DLG5 (P=0.023). However, the reported genetic variants that were indicated to be causative in the Caucasian population were completely absent in or were not associated with Japanese CD patients. These findings imply significant differences in genetic background with CD susceptibility among different ethnic groups and further indicate some difficulty of population-based studies.

Absence of mutation in the NOD2/CARD15 gene among 483 Japanese patients with Crohn's disease.

Chronic inflammatory bowel diseases (IBDs), specifically Crohn's disease (CD) and ulcerative colitis (UC), have increased significantly in western countries and Japan over the last decade, but very little is known about their pathogenesis. A candidate-gene approach recently identified NOD2/CARD15 as one susceptibility gene from the IBD1 locus on chromosome 16. Alterations in this gene were found in many Caucasian patients with CD; in particular, two nonsynonymous substitutions (R702W and G908R) and a frameshift mutation (1007fs) were shown to be independent risk factors for CD. We investigated DNA from 483 Japanese CD patients to detect those three mutations in NOD2/CARD15 by appropriate genotyping techniques, but found only an R702Q substitution in a single patient. Direct sequencing of DNA from 96 of our patients in the regions containing the three reported major mutations detected no sequence alterations of consequence. Our findings indicate that the NOD2/CARD15 gene is not a major contributor to CD susceptibility in the Japanese population.