Homozygosity for the CARD15 frameshift mutation 1007fs is predictive of early onset of Crohn's disease with ileal stenosis, entero-enteral fistulas, and frequent need for surgical intervention with high risk of re-stenosis

Genetic analysis of four consanguineous multiplex families with inflammatory bowel disease

Background

Family studies support a genetic predisposition to inflammatory bowel diseases (IBD), but known genetic variants only partially explain the disease heritability. Families with multiple affected individuals potentially harbour rare and high-impact causal variants. Long regions of homozygosity due to recent inbreeding may increase the risk of individuals bearing homozygous loss-of-function variants. This study aimed to identify rare and homozygous genetic variants contributing to IBD.

Methods

Four families with known consanguinity and multiple cases of IBD were recruited. In a family-specific analysis, we utilised homozygosity mapping complemented by whole-exome sequencing.

Results

We detected a single region of homozygosity shared by Crohn's disease cases from a family of Druze ancestry, spanning 2.6 Mb containing the NOD2 gene. Whole-exome sequencing did not identify any potentially damaging variants within the region, suggesting that non-coding variation may be involved. In addition, affected individuals in the families harboured several rare and potentially damaging homozygous variants in genes with a role in autophagy and innate immunity including LRRK1, WHAMM, DENND3, and C5.

Conclusion

This study examined the potential contribution of rare, high-impact homozygous variants in consanguineous families with IBD. While the analysis was not designed to achieve statistical significance, our findings highlight genes or loci that warrant further research. Non-coding variants affecting NOD2 may be of importance in Druze patients with Crohn's disease.

The Genetics of Postoperative Recurrence in Crohn Disease: A Systematic Review, Meta-analysis, and Framework for Future Work

Background

Recurrence following abdominal surgery in Crohn disease is over 50%. The impact of genetics on postoperative recurrence is not well defined.

Methods

A literature search was conducted where inclusion required an assessment, by genotype, of postoperative recurrence. The primary endpoint was odds of surgical recurrence.

Results

Twenty-eight studies identified a total of 6715 patients. Thirteen loci were identified as modifying the risk of recurrence. NOD2 was identified as a risk factor for recurrence by multiple works (cumulative odds ratio: 1.64, P = 0.003).

Conclusions

A NOD2 risk allele is associated with recurrence following surgery in Crohn disease. Progress in this area will require standardized reporting in future works.

Classifying Crohn's disease into colon-involving versus non-colon-involving groups is a better predictor of clinical outcomes than the Montreal classification

BACKGROUND

A suitable disease classification is essential for individualized therapy in patients with Crohn's disease (CD). Although a potential mechanistic classification of colon-involving and non-colon-involving disease was suggested by recent genetic and microbiota studies, the clinical implication has seldom been investigated. We aimed to explore the association of this colonic-based classification with clinical outcomes in patients with CD compared with the Montreal classification.

METHODS

This was a retrospective study of CD patients from a tertiary referral center. Patients were categorized into colon-involving and non-colon-involving disease, and according to the Montreal classification. Clinico-demographic data, medications, and surgeries were compared between the two classifications. The primary outcome was the need for major abdominal surgery.

RESULTS

Of 934 patients, those with colonic involvement had an earlier median (interquartile range) age of onset [23.0 (17.0-30.0) versus 26.0 (19.0-35.0) years, p = 0.001], higher frequency of perianal lesions (31.2% versus 14.5%, p < 0.001) and extraintestinal manifestations (21.8% versus 14.5%, p = 0.010), but lower frequency of stricture (B2) (16.3% versus 24.0%, p = 0.005), than those with non-colon-involving disease. Colon-involving disease was a protective factor against major abdominal surgery [hazard ratio, 0.689; 95% confidence interval (CI), 0.481-0.985; p = 0.041]. However, patients with colon-involving CD were more prone to steroids [odds ratio (OR), 1.793; 95% CI, 1.206-2.666; p = 0.004] and azathioprine/6-mercaptopurine (AZA/6-MP) treatment (OR, 1.732; 95% CI, 1.103-2.719; p = 0.017) than were patients with non-colon-involving disease. The Montreal classification was not predictive of surgery or steroids and AZA/6-MP treatment.

CONCLUSION

This study supports the rationale for disease classification based on the involvement of colon. This new classification of CD is a better predictor of clinical outcomes than the Montreal classification.

Links Between Inflammatory Bowel Disease and Chronic Obstructive Pulmonary Disease

Inflammatory bowel disease (IBD) and chronic obstructive pulmonary disease (COPD) are chronic inflammatory diseases of the gastrointestinal and respiratory tracts, respectively. These mucosal tissues bear commonalities in embryology, structure and physiology. Inherent similarities in immune responses at the two sites, as well as overlapping environmental risk factors, help to explain the increase in prevalence of IBD amongst COPD patients. Over the past decade, a tremendous amount of research has been conducted to define the microbiological makeup of the intestine, known as the intestinal microbiota, and determine its contribution to health and disease. Intestinal microbial dysbiosis is now known to be associated with IBD where it impacts upon intestinal epithelial barrier integrity and leads to augmented immune responses and the perpetuation of chronic inflammation. While much less is known about the lung microbiota, like the intestine, it has its own distinct, diverse microflora, with dysbiosis being reported in respiratory disease settings such as COPD. Recent research has begun to delineate the interaction or crosstalk between the lung and the intestine and how this may influence, or be influenced by, the microbiota. It is now known that microbial products and metabolites can be transferred from the intestine to the lung via the bloodstream, providing a mechanism for communication. While recent studies indicate that intestinal microbiota can influence respiratory health, intestinal dysbiosis in COPD has not yet been described although it is anticipated since factors that lead to dysbiosis are similarly associated with COPD. This review will focus on the gut-lung axis in the context of IBD and COPD, highlighting the role of environmental and genetic factors and the impact of microbial dysbiosis on chronic inflammation in the intestinal tract and lung.

Development of a uniform, very aggressive disease phenotype in all homozygous carriers of the NOD2 mutation p.Leu1007fsX1008 with Crohn's disease and active smoking status resulting in ileal stenosis requiring surgery

BACKGROUND

NOD2 variants are the strongest genetic predictors for susceptibility to Crohn's disease (CD). However, the clinical value of NOD2 on an individual patient level remains controversial. We aimed to define the predictive power of the major NOD2 mutations regarding complicated CD in a large single center cohort.

METHODS

1076 CD patients were prospectively genotyped for the three common CD-associated NOD2 mutations rs2066844, rs2066845, and rs2066847, followed by detailed genotype-phenotype analyses.

RESULTS

Overall, 434 CD patients (40.3%) carried at least one of the three main NOD2 mutations. A significantly higher minor allele frequency (15.6%) of the NOD2 frameshift mutation p.Leu1007fsX1008 (rs2066847) was seen in patients with aggressive disease compared to 8.2% in patients with mild disease (p = 2.6 x 10-5). Moreover, a total of 54 CD patients (5.0%) were homozygous for this NOD2 frameshift mutation. 100% of these patients had ileal disease compared to 82% of NOD2 wild-type carriers (p<0.0001). In homozygous carriers of the NOD2 frameshift mutation, 87% presented with ileal stenosis, 68.5% had fistulas, and 72.2% required CD-related surgery despite immunosuppressive therapy in 87% of these patients. All homozygous carriers of the 1007fs mutation who were active smokers had ileal stenosis and required CD-related surgery.

CONCLUSION

Homozygosity for Leu1007fsX1008 is an excellent biomarker for predicting complicated CD on an individual patient level. Active smoking and homozygosity for this mutation is associated with a 100% risk for developing ileal stenosis requiring CD-related surgery. In these patients, smoking cessation and early initiation of immunosuppressive strategies may be beneficial.

Multiplex gene expression profile in inflamed mucosa of patients with Crohn’s disease ileal localization: A pilot study

BACKGROUND

Crohn’s disease (CD) is a complex disorder resulting from the interaction of genetic, environmental, and microbial factors. The pathogenic process may potentially affect any segment of the gastrointestinal tract, but a selective location in the terminal ileum was reported in 50% of patients.

AIM

To characterize clinical sub-phenotypes (colonic and/or ileal) within the same disease, in order to identify new therapeutic targets.

METHODS

14 consecutive patients undergoing surgery for ileal CD were recruited for this study. Peripheral blood samples from each patient were collected and the main polymorphisms of the gene Card15/Nod2 (R702W, G908R, and 1007fs) were analyzed in each sample. In addition, tissue samples were taken from both the tract affected by CD and from the apparently healthy and disease-free margins (internal controls). We used a multiplex gene assay in specimens obtained from patients with ileal localization of CD to evaluate the simultaneous expression of 24 genes involved in the pathogenesis of the disease. We also processed surgery gut samples with routine light microscopy (LM) and transmission electron microscopy (TEM) techniques to evaluate their structural and ultrastructural features.

RESULTS

We found a significant increase of Th17 (IL17A and IL17F, IL 23R and CCR6) and Th1 (IFN-γ) gene expression in inflamed mucosa compared to non-inflamed sites of 14 CD patients. DEFB4 and HAMP, two genes coding for antimicrobial peptides, were also strongly activated in inflamed ileal mucosa, suggesting the overwhelming stimulation of epithelial cells by commensal microbiota. IFN-γ and CCR6 were more expressed in inflamed mucosa of CD patients with ileal localization compared with patients with colonic localization suggesting a more aggressive inflammation process in this site. Morphological analysis of the epithelial lining of Lieberkün crypts disclosed enhanced release activity from goblet mucocytes, whereas the lamina propria contained numerous cells pertaining to various lines.

CONCLUSION

We observed that the expression of ileal genes related to Th1 and Th17 activity is strongly activated as well as the expression of genes involved in microbiota regulation.

Molecular Profiling of Inflammatory Bowel Disease: Is It Ready for Use in Clinical Decision-Making?

Inflammatory bowel disease (IBD) is a heterogeneous disorder in terms of age at onset, clinical phenotypes, severity, disease course, and response to therapy. This underlines the need for predictive and precision medicine that can optimize diagnosis and disease management, provide more cost-effective strategies, and minimize the risk of adverse events. Ideally, we can leverage molecular profiling to predict the risk to develop IBD and disease progression. Despite substantial successes of genome-wide association studies in the identification of genetic variants affecting IBD susceptibility, molecular profiling of disease onset and progression as well as of treatment responses has lagged behind. Still, thanks to technological advances and good study designs, predicting phenotypes using genomics and transcriptomics in IBD has been rapidly evolving. In this review, we summarize the current status of prediction of disease risk, clinical course, and response to therapy based on clinical case presentations. We also discuss the potential and limitations of the currently used approaches.

Perioperative Care of Patients with Inflammatory Bowel Disease: Focus on Nutritional Support

Patients with inflammatory bowel disease (IBD) commonly require surgery despite the availability of an increasingly large repertoire of powerful immunosuppressive medications for the treatment of IBD. Optimizing patients' care preoperatively is crucial to obtaining good surgical outcomes. This review discusses preoperative assessment and management principles including assessing disease location and activity with cross-sectional or endoscopic imaging, addressing modifiable risk factors (i.e., stopping smoking, weaning steroids, and correcting anemia), and properly managing medications. The major focus of our literature review is the evaluation for malnutrition, a common finding that affects up to 70% of patients with IBD and a well-known, independent risk factor for adverse postoperative outcomes. Our review confirms that whenever feasible, oral or enteral nutrition (EN) is the preferred method of nutritional support; parenteral nutrition (PN) should be reserved for nutritionally deficient IBD patients unable to tolerate EN. In selected patients, recent data demonstrated that the use of preoperative PN resulted in improved nutritional status, fewer postoperative complications, and reduced disease severity. Our review highlights the need for well-designed, prospective trials investigating perioperative nutritional support in patients with IBD. Future studies should perform modern nutritional assessment, standardize for diet, and include patients with UC since this subset of patients is underrepresented in existing studies. In addition, relevant outcome of interest specific to Crohn's disease (CD) patients such as length of small bowel resected, number of anastomoses, and need for an ostomy should be included as these patients may require repeated small bowel resections.

Risk factors for postoperative recurrence of Crohn's disease with emphasis on surgical predictors

Intestinal resection for Crohn’s disease is not curative and postoperative recurrence rates remain high. Early detection of indices associated with recurrence and risk stratification are fundamental for the postoperative management of patients. Early endoscopy at 6-12 months is the “gold standard” procedure, whereas other modalities such as fecal calprotectin and imaging techniques can contribute to the diagnosis of recurrence. The purpose of this review is to summarize current data regarding risk factors correlated with postoperative relapse. Smoking is a well-established, modifiable risk factor. There are sufficient data that correlate penetrating disease, perianal involvement, extensive resections, prior surgery, histological features (plexitis and granulomas), and improper management after resection with high rates for recurrence. The literature provides conflicting data for other possible predictors, such as age, sex, family history of inflammatory bowel disease, location of disease, strictureplasties, blood transfusions, and postoperative complications, necessitating further evidence. On the other hand, surgical factors such as anastomotic configuration, open or laparoscopic approach, and microscopic disease at specimen margins when macroscopic disease is resected, seem not to be related with an increased risk of recurrence. Further recognition of histological features as well as gene-related factors are promising fields for research.

Nod2: A Critical Regulator of Ileal Microbiota and Crohn's Disease

The human intestinal tract harbors large bacterial community consisting of commensal, symbiotic, and pathogenic strains, which are constantly interacting with the intestinal immune system. This interaction elicits a non-pathological basal level of immune responses and contributes to shaping both the intestinal immune system and bacterial community. Recent studies on human microbiota are revealing the critical role of intestinal bacterial community in the pathogenesis of both systemic and intestinal diseases, including Crohn’s disease (CD). NOD2 plays a key role in the regulation of microbiota in the small intestine. NOD2 is highly expressed in ileal Paneth cells that provide critical mechanism for the regulation of ileal microbiota through the secretion of anti-bacterial compounds. Genome mapping of CD patients revealed that loss of function mutations in NOD2 are associated with ileal CD. Genome-wide association studies further demonstrated that NOD2 is one of the most critical genetic factor linked to ileal CD. The bacterial community in the ileum is indeed dysregulated in Nod2-deficient mice. Nod2-deficient ileal epithelia exhibit impaired ability of killing bacteria. Thus, altered interactions between ileal microbiota and mucosal immunity through NOD2 mutations play significant roles in the disease susceptibility and pathogenesis in CD patients, thereby depicting NOD2 as a critical regulator of ileal microbiota and CD.

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.

Epistatic interaction between TLR4 and NOD2 in patients with Crohn's Disease: relation with risk and phenotype in a Spanish cohort

Crohn's Disease is one of the two major forms of the Inflammatory Bowel Diseases and, although the etiology is not completely understood, the confluence of environmental and genetic factors has been demonstrated. The aim of this study was to determine the distribution of TLR4 variants in a Spanish cohort of Crohn's Disease patients and their relation with phenotype and common NOD2 variants. A total of 371 Crohn's Disease (CD) patients and 636 healthy controls (HC) were included. Single Nucleotide Polimorphisms (SNPs) in TLR4 (D299G and T399I) and NOD2 (R702W and G908R) detection was performed by a Taqman(®) Allelic Discrimination Assay. 1007insC NOD2 variant was analyzed using a PCR combined with fluorescent technology and the different alleles were determined depending on the PCR products size. D299G and T399I were related to CD only in patients carrying NOD2 variants (NOD2+/TLR4+ haplotype) (p=0.036; OR=1.924), increasing the risk to develop CD when 1007insC and TLR4 variants were both present (OR=4.886). We also described a strong association between mutant NOD2 and CD risk (p<0.001, OR=3.214). R702W, G908R and 1007insC were associated when they were considered separately (p<0.001; p=0.002; p<0.001, respectively). Moreover, the patients carrying any mutant D299G or T399I polymorphisms were predisposed to develop a stricturing disease (p=0.013; OR=2.391), especially in the presence of NOD2 mutation (p=0.002; OR=4.989). In this study, ileal disease was also associated with the presence of at least one NOD2 susceptibility allele (p=0.001; OR=3.838) and, the risk of ileal CD was increased if TLR4 variants were presents (p<0.050; OR=4.160). TLR4 variants were related to bowel perforation, independently of NOD2.

The NOD2 Single Nucleotide Polymorphism rs72796353 (IVS4+10 A>C) Is a Predictor for Perianal Fistulas in Patients with Crohn's Disease in the Absence of Other NOD2 Mutations

BACKGROUND

A previous study suggested an association of the single nucleotide polymorphism (SNP) rs72796353 (IVS4+10 A>C) in the NOD2 gene with susceptibility to Crohn's disease (CD). However, this finding has not been confirmed. Given that NOD2 variants still represent the most important predictors for CD susceptibility and phenotype, we evaluated the association of rs72796353 with inflammatory bowel disease (IBD) susceptibility and the IBD phenotype.

METHODOLOGY

Genomic DNA from 2256 Caucasians, including 1073 CD patients, 464 patients with ulcerative colitis (UC), and 719 healthy controls, was genotyped for the NOD2 SNP rs72796353 and the three main CD-associated NOD2 mutations rs2066844, rs2066845, and rs2066847. Subsequently, IBD association and genotype-phenotype analyses were conducted.

RESULTS

In contrast to the strong associations of the NOD2 SNPs rs2066844 (p=3.51 x 10(-3)), rs2066845 (p=1.54 x 10(-2)), and rs2066847 (p=1.61 x 10(-20)) with CD susceptibility, no significant association of rs72796353 with CD or UC susceptibility was found. However, in CD patients without the three main CD-associated NOD2 mutations, rs72796353 was significantly associated with the development of perianal fistulas (p=2.78 x 10(-7), OR 5.27, [95% CI 2.75-10.12] vs. NOD2 wild-type carriers).

CONCLUSION/SIGNIFICANCE

Currently, this study represents the largest genotype-phenotype analysis of the impact of the NOD2 variant rs72796353 on the disease phenotype in IBD. Our data demonstrate that in CD patients the IVS4+10 A>C variant is strongly associated with the development of perianal fistulas. This association is particularly pronounced in patients who are not carriers of the three main CD-associated NOD2 mutations, suggesting rs72796353 as additional genetic marker for the CD disease behaviour.

Crohn's disease: a role of gut microbiota and Nod2 gene polymorphisms in disease pathogenesis

Crohn's disease is a chronic immune-mediated intestinal inflammation targeted against a yet incompletely defined subset of commensal gut microbiota and occurs on the background of a genetic predisposition under the influence of environmental factors. Genome-wide association studies have identified about 70 genetic risk loci associated with Crohn's disease. The greatest risk for Crohn's disease represent polymorphisms affecting the CARD15 gene encoding nucleotide-binding oligomerization domain 2 (NOD2) which is an intracellular sensor for muramyl dipeptide, a peptidoglycan constituent of bacterial cell wall. The accumulated evidence suggests that gut microbiota represent an essential, perhaps a central factor in the induction and maintaining of Crohn's disease where dysregulation of normal co-evolved homeostatic relationships between intestinal microbiota and host mucosal immune system leads to intestinal inflammation. Taken together, these findings identify Crohn's disease as a syndrome of overlapping phenotypes that involves variable influences of genetic and environmental factors. A deeper understanding of different genetic abnormalities underlying Crohn's disease together with the identification of beneficial and harmful components of gut microbiota and their interactions are essential conditions for the categorization of Crohn's disease patients, which enable us to design more effective, preferably causative, individually tailored therapy.

Small bowel Crohn's disease: an emerging disease phenotype?

An increasing understanding of the pathogenesis of Crohn's disease (CD), coupled with improvements in therapeutic options, has promoted the concept of stratifying patients with CD into distinct disease phenotypes according to risk. Small bowel CD, due to the numerous non-specific potential symptoms and the anatomical location of the disease, is a particularly difficult phenotype to identify. The fact that the majority of de novo strictures occur in the ileum/ileo-colonic region ensures that recognition of small bowel involvement is essential. Certainly, it is becoming increasingly recognised due to improvements in imaging and endoscopic techniques. Both CT and MR enterography appear capable of accurately diagnosing small bowel CD. Furthermore, the development of capsule endoscopy and balloon-assisted enteroscopy allow direct visualisation of the small bowel. Limited data to date would suggest that small bowel CD is a difficult entity to treat even in the current era of the ever-expanding field of biological therapies. Further long-term follow-up studies are necessary using both small bowel capsule endoscopy and cross-sectional imaging to truly assess, firstly, whether small bowel CD is more resistant to treatment and, secondly, whether it has an effect over time in terms of complications. In the future, serological and genetic tests, coupled with the aforementioned investigations, will permit early diagnosis and early treatment of small bowel CD.

The NOD2 p.Leu1007fsX1008 mutation (rs2066847) is a stronger predictor of the clinical course of Crohn's disease than the FOXO3A intron variant rs12212067

Background

Very recently, a sub-analysis of genome-wide association scans revealed that the non-coding single nucleotide polymorphism (SNP) rs12212067 in the FOXO3A gene is associated with a milder course of Crohn's disease (CD) (Cell 2013;155:57–69). The aim of our study was to evaluate the clinical value of the SNP rs12212067 in predicting the severity of CD by correlating CD patient genotype status with the most relevant complications of CD such as stenoses, fistulas, and CD-related surgery.

Methodology/Principal Findings

We genotyped 550 CD patients for rs12212067 (FOXO3A) and the three common CD-associated NOD2 mutations rs2066844, rs2066847, and rs2066847 and performed genotype-phenotype analyses.

Results

No significant phenotypic differences were found between the wild-type genotype TT of the FOXO3A SNP rs12212067 and the minor genotypes TG and GG independently from NOD2 variants. The allele frequency of the minor G allele was 12.7%. Age at diagnosis, disease duration, body mass index, surgery rate, stenoses, fistula, need for immunosuppressive therapy, and disease course were not significantly different. In contrast, the NOD2 mutant p.Leu1007fsX1008 (rs2066847) was highly associated with penetrating CD (p = 0.01), the development of fistulas (p = 0.01) and stenoses (p = 0.01), and ileal disease localization (p = 0.03). Importantly, the NOD2 SNP rs2066847 was a strong separator between an aggressive and a mild course of CD (p = 2.99×10⁻⁵), while the FOXO3A SNP rs12212067 did not separate between mild and aggressive CD behavior in our cohort (p = 0.35). 96.2% of the homozygous NOD2 p.Leu1007fsX1008 carriers had an aggressive disease behavior compared to 69.3% of the patients with the NOD2 wild-type genotype (p = 0.007).

Conclusion/Significance

In clinical practice, the NOD2 variant p.Leu1007fsX1008 (rs2066847), in particular in homozygous form, is a much stronger marker for a severe clinical phenotype than the FOXO3A rs12212067 SNP for a mild disease course on an individual patient level despite its important impact on the inflammatory response of monocytes.

Can we predict the high-risk patient?

BACKGROUND

While therapeutic strategies able to change the natural history of inflammatory bowel diseases (IBD) are being developed, factors predicting aggressive disease are needed to be able to choose the appropriate therapeutic strategy for the individual patient based on the risk/benefit ratio. The aim of this review is to focus on the tools assisting the clinician in routine practice regarding the prediction of disease evolution.

METHODS

A literature review was performed, which was mainly based on PubMed search, using the following terms: Crohn's disease, ulcerative colitis, inflammatory bowel disease, genetics, serology, biomarkers, endoscopy, C-reactive protein, faecal calprotectin, disease evolution and complications.

RESULTS

For the prediction of disease evolution, clinical characteristics, particularly disease location and behaviour, are probably currently the most useful. In addition, a series of biomarkers, including genetic, serological and inflammatory markers, as well as characteristics of endoscopic lesions may have an added value.

CONCLUSIONS

Simple clinical, biological and endoscopic tools may help the clinician in predicting disease evolution in IBD. However, these tools are still insufficient, and prospective evaluation of new genetic and biological markers are needed.

NOD2 gene mutations in ulcerative colitis: useless or misunderstood?

PURPOSE

NOD2 mutations have been linked to an increased risk of Crohn's disease and to some of its phenotypes. The association between NOD2 mutations and susceptibility to ulcerative colitis (UC) remains somewhat controversial and potential correlations between these mutations and UC phenotype have not been studied.

AIM

To assess whether NOD2 mutations are a risk factor for UC in Portugal and if there are any genotype-phenotype correlations in these patients.

METHODS

The three main NOD2 mutations were searched in 200 patients with UC and in 202 healthy controls.

RESULTS

NOD2 mutations were present in 28 patients with UC (14.0 %) and in 27 controls (13.4 %) (p = 0.853). Mutation carriers were more likely to receive steroids during the first year of disease than non-carriers (54.2 % vs. 29.6 %, p = 0.018) and among these patients the need for intravenous administration was more frequent in those with the R702W polymorphism (90.0 % vs. 45.5 %, p = 0.014). In patients with severe colitis admitted for intravenous steroids, a greater proportion of mutation carriers was considered intravenous-steroid refractory and required salvage therapy (90.0 % vs. 38.1 %, p = 0.004). Patients with NOD2 mutation were submitted to colectomy more frequently than non-carriers (17.9 % vs. 4.1 %. p = 0.015). No correlation with the need for immunosuppressants/immunomodulators was found.

CONCLUSIONS

In the Portuguese population, NOD2 mutations do not increase the risk of UC but are associated with a more aggressive course including greater need of steroids in the first year, increased incidence of intravenous-steroid refractoriness and a higher colectomy rate.

Prediction of Crohn’s disease aggression through NOD2/CARD15 gene sequencing in an Australian cohort

AIM: To investigate the association between mutations in oligomerisation domain 2/caspase recruitment domains 15 (NOD2/CARD15) and the natural history of Crohn’s disease (CD) to identify patients who would benefit from early aggressive medical intervention.

METHODS: We recruited thirty consecutive unrelated CD patients with a history of ileo-caecal or small bowel resection during the period 1980-2000; Fifteen patients of these had post-operative relapse that required further surgery and fifteen did not. Full sequencing of the NOD2/CARD15 gene using dHPLC for exons 3, 5, 7, 10 and 12 and direct sequencing for exons 2, 4, 6, 8, 9 and 11 was conducted. CD patients categorized as carrying variants were anyone with at least 1 variant of the NOD2/CARD15 gene.

RESULTS: About 13.3% of the cohort (four patients) carried at least one mutant allele of 3020insC of the NOD2/CARD15 gene. There were 20 males and 10 females with a mean age of 43.3 years (range 25-69 years). The mean follow up was 199.6 mo and a median of 189.5 mo. Sixteen sequence variations within the NOD2/CARD15 gene were identified, with 9 of them occurring with an allele frequency of greater than 10 %. In this study, there was a trend to suggest that patients with the 3020insC mutation have a higher frequency of operations compared to those without the mutation. Patients with the 3020insC mutation had a significantly shorter time between the diagnosis of CD and initial surgery. This study included Australian patients of ethnically heterogenous background unlike previous studies conducted in different countries.

CONCLUSION: These findings suggest that patients carrying NOD2/CARD15 mutations follow a rapid and more aggressive form of Crohn’s disease showing a trend for multiple surgical interventions and significantly shorter time to early surgery.

Intestinal DMBT1 expression is modulated by Crohn's disease-associated IL23R variants and by a DMBT1 variant which influences binding of the transcription factors CREB1 and ATF-2

OBJECTIVES

DMBT is an antibacterial pattern recognition and scavenger receptor. In this study, we analyzed the role of DMBT1 single nucleotide polymorphisms (SNPs) regarding inflammatory bowel disease (IBD) susceptibility and examined their functional impact on transcription factor binding and downstream gene expression.

METHODS

Seven SNPs in the DMBT1 gene region were analyzed in 2073 individuals including 818 Crohn's disease (CD) patients and 972 healthy controls in two independent case-control panels. Comprehensive epistasis analyses for the known CD susceptibility genes NOD2, IL23R and IL27 were performed. The influence of IL23R variants on DMBT1 expression was analyzed. Functional analysis included siRNA transfection, quantitative PCR, western blot, electrophoretic mobility shift and luciferase assays.

RESULTS

IL-22 induces DMBT1 protein expression in intestinal epithelial cells dependent on STAT3, ATF-2 and CREB1. IL-22 expression-modulating, CD risk-associated IL23R variants influence DMBT1 expression in CD patients and DMBT1 levels are increased in the inflamed intestinal mucosa of CD patients. Several DMBT1 SNPs were associated with CD susceptibility. SNP rs2981804 was most strongly associated with CD in the combined panel (p = 3.0 × 10(-7), OR 1.42; 95% CI 1.24-1.63). All haplotype groups tested showed highly significant associations with CD (including omnibus P-values as low as 6.1 × 10(-18)). The most strongly CD risk-associated, non-coding DMBT1 SNP rs2981804 modifies the DNA binding sites for the transcription factors CREB1 and ATF-2 and the respective genomic region comprising rs2981804 is able to act as a transcriptional regulator in vitro. Intestinal DMBT1 expression is decreased in CD patients carrying the rs2981804 CD risk allele.

CONCLUSION

We identified novel associations of DMBT1 variants with CD susceptibility and discovered a novel functional role of rs2981804 in regulating DMBT1 expression. Our data suggest an important role of DMBT1 in CD pathogenesis.

Genetic factors conferring an increased susceptibility to develop Crohn's disease also influence disease phenotype: results from the IBDchip European Project

OBJECTIVE

Through genome-wide association scans and meta-analyses thereof, over 70 genetic loci (Crohn's disease (CD) single nucleotide polymorphisms (SNPs)) are significantly associated with CD. We aimed to investigate the influence of CD-SNPs and basic patient characteristics on CD clinical course, and develop statistical models to predict CD clinical course.

DESIGN

This retrospective study included 1528 patients with CD with more than 10 years of follow-up from eight European referral hospitals. CD outcomes of interest were ileal (L1), colonic (L2) and ileocolonic disease location (L3); stenosing (B2) or penetrating behaviour (B3); perianal disease; extraintestinal manifestations; and bowel resection. A complicated disease course was defined as stenosing or penetrating behaviour, perianal disease and/or bowel resection. Association between CD-SNPs or patient characteristics and specified outcomes was studied.

RESULTS

Several CD-SNPs and clinical characteristics were statistically associated with outcomes of interest. The NOD2 gene was the most important genetic factor, being an independent predictive factor for ileal location (p=2.02 × 10(-06), OR=1.90), stenosing (p=3.16 × 10(-06), OR=1.82) and penetrating (p=1.26 × 10(-02), OR=1.25) CD behaviours, and need for surgery (p=2.28 × e-05, OR=1.73), and as such was also the strongest factor associated with a complicated disease course (p=6.86 × 10(-06), OR=2.96). Immunomodulator (azathioprine/6-mercaptopurine and methotrexate) use within 3 years after diagnosis led to a reduction in bowel stenoses (p=1.48 × 10(-06), OR=0.35) and surgical rate (p=1.71 × 10(-07), OR=0.34). Association between each outcome and genetic scores, created using significant SNPs in the univariate analysis, revealed large differences in the probability of developing fistulising disease (IL23R, LOC441108, PRDM1, NOD2; p=9.64e-4, HR=1.43), need for surgery (IRGM, TNFSF15, C13ORF31, NOD2; p=7.12 × 10(-03), HR=1.35), and stenosing disease (NOD2, JAK2, ATG16L1; p=3.01 × 10(-02), HR=1.29) among patients with low and high score.

CONCLUSIONS

This large multicentre cohort study has found several genetic and clinical factors influencing the clinical course of CD. NOD2 and early immunomodulator use are the clinically most meaningful predictors for its clinical course.

Recent advances: Personalised use of current Crohn's disease therapeutic options

Several aspects of the management of Crohn's disease (CD) are shared between patients. The goal of all therapies should be to achieve clinical and endoscopic remission in a timely manner to avoid disease progression and abdominal resections. The way this goal is achieved may differ and predicting how the disease will evolve, what the most appropriate therapy with the highest chance of success will be, how long a therapy needs to be continued, and what the intensity of follow-up should be are more difficult questions and require an individualised approach. Clinical parameters have been suggested to aid in the therapeutic decision process but lack specificity. Although much promise has been put in molecular markers, these have not yet found their way to the clinic. More recently, clinicians have started to gain interest in drug level monitoring to adapt doses of immunomodulators and/or anti-tumour necrosis factor antibodies in an individualised manner. An increasing number of studies show that therapeutic drug monitoring can help physicians to improve and personalise the management of their patients. What is needed now are pharmaco-economic studies showing that personalised management of CD is cost effective.

The effect of NOD2 polymorphism on postsurgical recurrence in Crohn's disease: a systematic review and meta-analysis of available literature

BACKGROUND

Up to 70% of patients requiring surgery for Crohn's disease (CD) develop recurrence within 10 years. Unequivocal markers predicting recurrence are needed to tailor postoperative therapy appropriately. NOD2 (nucleotide-binding oligomerization domain 2) polymorphisms increase the risk of developing CD; however, their ability to predict recurrence is uncertain. This study aims to determine the association between NOD2 variants and surgical recurrence after initial disease-modifying surgery.

METHODS

A comprehensive search for published series comparing the effect of NOD2 polymorphisms on postoperative surgical recurrence in patients with CD was performed. Random-effects methods were used to combine data.

RESULTS

Six cohort studies comprising 1003 patients with CD were included. A total of 340 patients (33.9%) expressed at least 1 of the 3 common NOD2 polymorphisms. The 1003 patients underwent surgical resection with 335 (33%) developing surgical recurrence. Of 340 NOD2-expressing patients, 130 (39%) required further resection, whereas 202 of 663 patients (30.5%) without the variant underwent repeat resection. NOD2 was not significantly associated with surgical recurrence (odds ratio: 1.58, 95% confidence interval: 0.97-2.57, P = 0.064), most likely because of study heterogeneity (Cochran Q: 12.36, P = 0.030, I: 59.6%). The sensitivity of any mutation in predicting disease recurrence was 39.7% and specificity was 69%, with the area under the receiver operating characteristic curve being 0.64.

CONCLUSIONS

Patients with CD with a NOD2 polymorphism do not have an increased risk of surgical recurrence compared with patients without the variant. These data provide insufficient evidence to support postoperative medical prophylaxis based solely on the presence of NOD2 polymorphism.

IRGM variants and susceptibility to inflammatory bowel disease in the German population

Background & Aims

Genome-wide association studies identified the autophagy gene IRGM to be strongly associated with Crohn's disease (CD) but its impact in ulcerative colitis (UC), its phenotypic effects and potential epistatic interactions with other IBD susceptibility genes are less clear which we therefore analyzed in this study.

Methodology/Principal Findings

Genomic DNA from 2060 individuals including 817 CD patients, 283 UC patients, and 961 healthy, unrelated controls (all of Caucasian origin) was analyzed for six IRGM single nucleotide polymorphisms (SNPs) (rs13371189, rs10065172 = p.Leu105Leu, rs4958847, rs1000113, rs11747270, rs931058). In all patients, a detailed genotype-phenotype analysis and testing for epistasis with the three major CD susceptibility genes NOD2, IL23R and ATG16L1 were performed.

Our analysis revealed an association of the IRGM SNPs rs13371189 (p = 0.02, OR 1.31 [95% CI 1.05–1.65]), rs10065172 = p.Leu105Leu (p = 0.016, OR 1.33 [95% CI 1.06–1.66]) and rs1000113 (p = 0.047, OR 1.27 [95% CI 1.01–1.61]) with CD susceptibility. There was linkage disequilibrium between these three IRGM SNPs. In UC, several IRGM haplotypes were weakly associated with UC susceptibility (p<0.05). Genotype-phenotype analysis revealed no significant associations with a specific IBD phenotype or ileal CD involvement. There was evidence for weak gene-gene-interaction between several SNPs of the autophagy genes IRGM and ATG16L1 (p<0.05), which, however, did not remain significant after Bonferroni correction.

Conclusions/Significance

Our results confirm IRGM as susceptibility gene for CD in the German population, supporting a role for the autophagy genes IRGM and ATG16L1 in the pathogenesis of CD.

PTGER4 expression-modulating polymorphisms in the 5p13.1 region predispose to Crohn's disease and affect NF-κB and XBP1 binding sites

Background

Genome-wide association studies identified a PTGER4 expression-modulating region on chromosome 5p13.1 as Crohn's disease (CD) susceptibility region. The study aim was to test this association in a large cohort of patients with inflammatory bowel disease (IBD) and to elucidate genotypic and phenotypic interactions with other IBD genes.

Methodology/Principal Findings

A total of 7073 patients and controls were genotyped: 844 CD and 471 patients with ulcerative colitis and 1488 controls were analyzed for the single nucleotide polymorphisms (SNPs) rs4495224 and rs7720838 on chromosome 5p13.1. The study included two replication cohorts of North American (CD: n = 684; controls: n = 1440) and of German origin (CD: n = 1098; controls: n = 1048). Genotype-phenotype, epistasis and transcription factor binding analyses were performed. In the discovery cohort, an association of rs4495224 (p = 4.10×10⁻⁵; 0.76 [0.67–0.87]) and of rs7720838 (p = 6.91×10⁻⁴; 0.81 [0.71–0.91]) with susceptibility to CD was demonstrated. These associations were confirmed in both replication cohorts. In silico analysis predicted rs4495224 and rs7720838 as essential parts of binding sites for the transcription factors NF-κB and XBP1 with higher binding scores for carriers of the CD risk alleles, providing an explanation of how these SNPs might contribute to increased PTGER4 expression. There was no association of the PTGER4 SNPs with IBD phenotypes. Epistasis detected between 5p13.1 and ATG16L1 for CD susceptibility in the discovery cohort (p = 5.99×10⁻⁷ for rs7720838 and rs2241880) could not be replicated in both replication cohorts arguing against a major role of this gene-gene interaction in the susceptibility to CD.

Conclusions/Significance

We confirmed 5p13.1 as a major CD susceptibility locus and demonstrate by in silico analysis rs4495224 and rs7720838 as part of binding sites for NF-κB and XBP1. Further functional studies are necessary to confirm the results of our in silico analysis and to analyze if changes in PTGER4 expression modulate CD susceptibility.

Genotype/phenotype analyses for 53 Crohn's disease associated genetic polymorphisms

Background & Aims

Recent studies reported a role for more than 70 genes or loci in the susceptibility to Crohn’s disease (CD). However, the impact of these associations in clinical practice remains to be defined. The aim of the study was to analyse the relationship between genotypes and phenotypes for the main 53 CD-associated polymorphisms.

Method

A cohort of 798 CD patients with a median follow up of 7 years was recruited by tertiary adult and paediatric gastroenterological centres. A detailed phenotypic description of the disease was recorded, including clinical presentation, response to treatments and complications. The participants were genotyped for 53 CD-associated variants previously reported in the literature and correlations with clinical sub-phenotypes were searched for. A replication cohort consisting of 722 CD patients was used to further explore the putative associations.

Results

The NOD2 rare variants were associated with an earlier age at diagnosis (p = 0.0001) and an ileal involvement (OR = 2.25[1.49–3.41] and 2.77 [1.71–4.50] for rs2066844 and rs2066847, respectively). Colonic lesions were positively associated with the risk alleles of IL23R rs11209026 (OR = 2.25 [1.13–4.51]) and 6q21 rs7746082 (OR = 1.60 [1.10–2.34] and negatively associated with the risk alleles of IRGM rs13361189 (OR = 0.29 [0.11–0.74]) and DEFB1 rs11362 (OR = 0.50 [0.30–0.80]). The ATG16L1 and IRGM variants were associated with a non-inflammatory behaviour (OR = 1.75 [1.22–2.53] and OR = 1.50 [1.04–2.16] respectively). However, these associations lost significance after multiple testing corrections. The protective effect of the IRGM risk allele on colonic lesions was the only association replicated in the second cohort (p = 0.03).

Conclusions

It is not recommended to genotype the studied polymorphisms in routine practice.

Clinical predictors at diagnosis of disabling pediatric Crohn's disease

BACKGROUND

Identification of children with Crohn's disease (CD) at high risk of disabling disease would be invaluable in guiding initial therapy. Our study aimed to identify predictors at diagnosis of a subsequent disabling course in a population-based cohort of patients with pediatric-onset CD.

METHODS

Among 537 patients with pediatric CD diagnosed at <17 years of age, 309 (57%) with 5-year follow-up were included. Clinical and demographic factors associated with subsequent disabling CD were studied. Three definitions of disabling CD were used: Saint-Antoine and Liège Hospitals' definitions and a new pediatric definition based on the presence at maximal follow-up of: 1) growth delay defined by body mass index (BMI), weight or height lower than -2 SD Z score; and 2) at least one intestinal resection or two anal interventions. Predictors were determined using multivariate analyses and their accuracy using the kappa method considering a relevant value ≥ 0.6.

RESULTS

According to the Saint-Antoine definition, the rate of disabling CD was 77% and predictors were complicated behavior and L1 location. According to the Liège definition, the rate was 37% and predictors included behavior, upper gastrointestinal disease, and extraintestinal manifestations. According to the pediatric definition, the rate of disabling CD was 15%, and predictors included complicated behavior, age <14, and growth delay at diagnosis. Kappa values for each combination of predictors were, respectively, 0.2, 0.3, and 0.2 and were nonrelevant.

CONCLUSIONS

Clinical parameters at diagnosis are insufficient to predict a disabling course of pediatric CD. More complex models including serological and genetic biomarkers should be tested.

NOD2 gene variants are a risk factor for culture-positive spontaneous bacterial peritonitis and monomicrobial bacterascites in cirrhosis

BACKGROUND

Spontaneous bacterial peritonitis (SBP) is considered as result of bacterial translocation from the gastrointestinal lumen to the mesenteric lymph nodes and subsequent circulation. Variants of the NOD2 gene contribute to bacterial translocation and were associated with SBP in a recent study.

METHODS

We determined common NOD2 variants by TaqMan polymerase chain reaction and analysed the ascitic fluid neutrophil count and bacterial culture results in 175 prospectively characterized hospitalized patients with decompensated cirrhosis who underwent diagnostic paracentesis in two German centres.

RESULTS

Ten patients presented with culture-positive SBP, 19 with culture-negative SBP and six had bacterascites. Minor allele frequencies for R702W, G908R and 1007fs in subjects with sterile non-neutrocytic ascites were 3.2, 2.5 and 2.5% respectively. Patients with SBP [odds ratio (OR) 2.7; P=0.036], culture-positive SBP (OR 6.0; P=0.012) and bacterascites (OR 6.0; P=0.050) were more often carriers of NOD2 variants than patients with sterile non-neutrocytic ascites. The mutations 1007fs and G908R were associated with culture-positive SBP (P ≤ 0.005) and R702W with bacterascites (P=0.014). There was no significant association of NOD2 variants with culture-negative SBP (OR 1.6; P=0.493). In logistic regression, previous SBP, a higher model for end-stage liver disease (MELD) score and the presence of a NOD2 variant were independent predictors of ascitic fluid infection. The median survival was insignificantly shorter in patients with NOD2 variants (268 vs. 339 days; P=0.386). In patients without hepatocellular carcinoma at study entry (N=148), NOD2 was a predictor of survival after adjustment for the MELD score and age (hazard ratio 1.89; P=0.045).

CONCLUSION

NOD2 variants increase the risk for culture-positive SBP and bacterascites in cirrhosis and may affect survival.

NOD2 polymorphism predicts response to treatment in Crohn's disease--first steps to a personalized therapy

BACKGROUND AND AIMS

Great efforts have been made to predict disease behavior over time and the response to treatment in Crohn's disease (CD). Such understanding could personalize therapy. Early introduction of more aggressive therapies to patients at high risk and no introduction of predictable refractory treatments could become possible. We hence tested the influence of the NOD2 carrier status on treatment response.

PATIENTS AND METHODS

In 185 CD patients (age 45 ± 9.8 years, female n = 108, minimum disease duration 10 years), the three most common polymorphisms (p.Arg702Trp, p.Gly908Arg, p.Leu1007fsX1008) of NOD2 were tested by polymerase chain reaction and sequencing. Detailed clinical and medical history were obtained with a standardized questionnaire and by reviewing the medical charts. Treatments introduced were chosen by physicians blinded to genotype data.

RESULTS

The frequency of the NOD2 variant allele was about one-third (67, 30.2%) of CD patients. NOD2 carriers were more often treated with systemic and locally active steroids and with an immunosuppressant (Azathioprine/6-MP). NOD2 mutation carrier status was more often associated with systemic steroid [8.9% vs. wild-type (WT) 1.2%, P = 0.0086] and local-steroid refractory (14.9% vs. WT 3.5%; P = 0.001). The WT patients were significantly higher refractory to immunosuppressant (12.8% vs. NOD2 carriers, 0.5%, P = 0.03). Most WT patients were treated with TNF-α antagonists and remission rates were significantly higher in this group after 1 year of treatment (84% vs. NOD2 carriers, 33%, P = 0.07).

CONCLUSIONS

The study presents first hints for the NOD2 carrier status to be predictive for response to therapy. A higher percentage of CD patients with NOD2 mutation carrier status was steroid refractory but could be treated well with immunosuppressants. The WT status showed a higher response to steroids and remission rates within 1 year of anti-TNF-α therapy. On the way to personalized medicine, this approach should be further investigated in larger studies.

CEACAM6 gene variants in inflammatory bowel disease

BACKGROUND

The carcinoembryonic antigen-related cell adhesion molecule 6 (CEACAM6) acts as a receptor for adherent-invasive E. coli (AIEC) and its ileal expression is increased in patients with Crohn's disease (CD). Given its contribution to the pathogenesis of CD, we aimed to investigate the role of genetic variants in the CEACAM6 region in patients with inflammatory bowel diseases (IBD).

METHODOLOGY

In this study, a total of 2,683 genomic DNA samples (including DNA from 858 CD patients, 475 patients with ulcerative colitis (UC), and 1,350 healthy, unrelated controls) was analyzed for eight CEACAM6 SNPs (rs10415946, rs1805223 = p.Pro42Pro, rs4803507, rs4803508, rs11548735 = p.Gly239Val, rs7246116 = pHis260His, rs2701, rs10416839). In addition, a detailed haplotype analysis and genotype-phenotype analysis were performed. Overall, our genotype analysis did not reveal any significant association of the investigated CEACAM6 SNPs and haplotypes with CD or UC susceptibility, although certain CEACAM6 SNPs modulated CEACAM6 expression in intestinal epithelial cell lines. Despite its function as receptor of AIEC in ileal CD, we found no association of the CEACAM6 SNPs with ileal or ileocolonic CD. Moreover, there was no evidence of epistasis between the analyzed CEACAM6 variants and the main CD-associated NOD2, IL23R and ATG16L1 variants.

CONCLUSIONS

This study represents the first detailed analysis of CEACAM6 variants in IBD patients. Despite its important role in bacterial attachment in ileal CD, we could not demonstrate a role for CEACAM6 variants in IBD susceptibility or regarding an ileal CD phenotype. Further functional studies are required to analyze if these gene variants modulate ileal bacterial attachment.

The prognostic power of the NOD2 genotype for complicated Crohn's disease: a meta-analysis

OBJECTIVES

Crohn's disease is often purely inflammatory at presentation, but most patients develop strictures and fistulae over time (complicated disease). Many studies have suggested that nucleotide-binding oligomerization domain 2 (NOD2) mutations are associated with a varying but increased risk of complicated disease. An accurate and sufficiently powerful predictor of complicated disease could justify the early use of biological therapy in high-risk individuals. We performed a systematic review and meta-analysis to obtain accurate estimates of the predictive power of the identified mutations (such as p.R702W, P.G908R, and p.Leu1007fsX1008) in NOD2 for the risk of complicated disease.

METHODS

An electronic search of MEDLINE, Embase, and Web of Science identified 917 relevant papers. Inclusion required specification of genetic mutations at the individual level and disease phenotypes by Vienna classification (inflammatory (B1), stricturing (B2), and fistulizing (B3)). A total of 49 studies met these criteria, which included 8,893 subjects, 2,897 of whom had NOD2 mutations. Studies were weighted by median disease duration. Studies not providing duration data were weighted at the level of the study with the shortest disease duration (3.9 years).

RESULTS

The relative risk (RR) of the presence of any NOD2 mutant allele for complicated disease (B2 or B3) was 1.17 (95% confidence interval (95% CI) 1.10-1.24; P<0.001). P.G908R was associated with an RR of complicated disease of 1.33 (95% CI 1.11-1.60; P=0.002). NOD2 did not predict perianal disease (P=0.4). The RR of surgery was 1.58 (95% CI 1.38-1.80; P<0.001). There was substantial heterogeneity across all studies (I(2)=66.7%). On the basis of logistic regression of these data, the sensitivity of any mutation in predicting complicated disease was 36% and specificity was 73%, with the area under the receiver operating characteristic curve 0.56.

CONCLUSIONS

The presence of a single NOD2 mutation predicted an 8% increase in the risk for complicated disease (B2 or B3), and a 41% increase with 2 mutations. Surgery risk is increased by 58% with any NOD2 mutation, whereas perianal disease was unchanged. The predictive power associated with a single NOD2 mutation is weak. The RR of any NOD2 mutations for complicated disease was only 17% across 36 studies. However, the presence of two NOD2 mutations had 98% specificity for complicated disease. These data provide insufficient evidence to support top-down therapy based solely on single NOD2 mutations, but suggest that targeted early-intensive therapy for high-risk patients with two NOD2 mutations might be beneficial, if prospective trials can demonstrate changes in the natural history in this subset of patients.

Paneth cells, antimicrobial peptides and maintenance of intestinal homeostasis

Building and maintaining a homeostatic relationship between a host and its colonizing microbiota entails ongoing complex interactions between the host and the microorganisms. The mucosal immune system, including epithelial cells, plays an essential part in negotiating this equilibrium. Paneth cells (specialized cells in the epithelium of the small intestine) are an important source of antimicrobial peptides in the intestine. These cells have become the focus of investigations that explore the mechanisms of host-microorganism homeostasis in the small intestine and its collapse in the processes of infection and chronic inflammation. In this Review, we provide an overview of the intestinal microbiota and describe the cell biology of Paneth cells, emphasizing the composition of their secretions and the roles of these cells in intestinal host defence and homeostasis. We also highlight the implications of Paneth cell dysfunction in susceptibility to chronic inflammatory bowel disease.

Paneth cells, antimicrobial peptides and maintenance of intestinal homeostasis

Building and maintaining a homeostatic relationship between a host and its colonizing microbiota entails ongoing complex interactions between the host and the microorganisms. The mucosal immune system, including epithelial cells, plays an essential part in negotiating this equilibrium. Paneth cells (specialized cells in the epithelium of the small intestine) are an important source of antimicrobial peptides in the intestine. These cells have become the focus of investigations that explore the mechanisms of host-microorganism homeostasis in the small intestine and its collapse in the processes of infection and chronic inflammation. In this Review, we provide an overview of the intestinal microbiota and describe the cell biology of Paneth cells, emphasizing the composition of their secretions and the roles of these cells in intestinal host defence and homeostasis. We also highlight the implications of Paneth cell dysfunction in susceptibility to chronic inflammatory bowel disease.

The NOD2 single nucleotide polymorphisms rs2066843 and rs2076756 are novel and common Crohn's disease susceptibility gene variants

Background

The aims were to analyze two novel NOD2 variants (rs2066843 and rs2076756) in a large cohort of patients with inflammatory bowel disease and to elucidate phenotypic consequences.

Methodology/Principal Findings

Genomic DNA from 2700 Caucasians including 812 patients with Crohn's disease (CD), 442 patients with ulcerative colitis (UC), and 1446 healthy controls was analyzed for the NOD2 SNPs rs2066843 and rs2076756 and the three main CD-associated NOD2 variants p.Arg702Trp (rs2066844), p.Gly908Arg (rs2066847), and p.Leu1007fsX1008 (rs2066847). Haplotype and genotype-phenotype analyses were performed. The SNPs rs2066843 (p = 3.01×10⁻⁵, OR 1.48, [95% CI 1.23-1.78]) and rs2076756 (p = 4.01×10⁻⁶; OR 1.54, [95% CI 1.28-1.86]) were significantly associated with CD but not with UC susceptibility. Haplotype analysis revealed a number of significant associations with CD susceptibility with omnibus p values <10⁻¹⁰. The SNPs rs2066843 and rs2076756 were in linkage disequilibrium with each other and with the three main CD-associated NOD2 mutations (D'>0.9). However, in CD, SNPs rs2066843 and rs2076756 were more frequently observed than the other three common NOD2 mutations (minor allele frequencies for rs2066843 and rs2076756: 0.390 and 0.380, respectively). In CD patients homozygous for these novel NOD2 variants, genotype-phenotype analysis revealed higher rates of a penetrating phenotype (rs2076756: p = 0.015) and fistulas (rs2076756: p = 0.015) and significant associations with CD-related surgery (rs2076756: p = 0.003; rs2066843: p = 0.015). However, in multivariate analysis only disease localization (p<2×10⁻¹⁶) and behaviour (p = 0.02) were significantly associated with the need for surgery.

Conclusion/Significance

The NOD2 variants rs2066843 and rs2076756 are novel and common CD susceptibility gene variants.

The presence of fistulas and NOD2 homozygosity strongly predict intestinal stenosis in Crohn's disease independent of the IL23R genotype

BACKGROUND AND AIMS

We analyzed the prevalence of concomitant intestinal stenosis in patients with fistulizing Crohn's disease (CD), including the NOD2/CARD15 and IL23R genotype status.

METHODS

Medical records of n = 1,110 patients with inflammatory bowel diseases were screened for patients with fistulizing and stricturing CD. Study inclusion required diagnosis of stenosis made within 6 months of diagnosing fistulas. CD-associated NOD2 and IL23R variants were genotyped. Similarly, we prospectively investigated 42 patients presenting with fistulizing CD.

RESULTS

In the retrospective study (n = 333 CD patients), fistulas were found in 145 (43.5%) patients and stenoses in 223 (67.0%) patients. Concomitant stenosis was diagnosed in 125 patients with fistulas resulting in a positive predictive value (PPV) of 86.2% for fistulas predicting intestinal stenosis (p = 5.53 x 10(-11); OR 5.74, 95% CI 3.22-10.50). In logistic regression analysis, presence of fistulas (OR 4.51; 95% CI 2.54-8.01, p = 2.68 x 10(-7)) and disease duration (OR 1.09; 95% CI 1.05-1.13; p = 3.19 x 10(-6)) were strongly associated with intestinal stenosis. NOD2 genotype information, but not IL23R status, increased the PPV for the correct diagnosis of stenosis (PPV = 89.9%). All homozygous carriers (100%) of NOD2 variants with fistulizing CD were diagnosed with stenosis; 1007fs homozygotes were found more often among patients with fistulas and stenoses than in patients without stenoses and fistulas (p = 0.00037). Similar results were found in the prospective analysis, in which 83.3% of the patients with fistulizing CD had concomitant stenosis.

CONCLUSION

Fistulizing CD is strongly associated with concomitant intestinal stenosis, particularly in homozygous carriers of NOD2 mutations.

Evidence for STAT4 as a common autoimmune gene: rs7574865 is associated with colonic Crohn's disease and early disease onset

Background

Recent studies demonstrated an association of STAT4 variants with systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA), indicating that multiple autoimmune diseases share common susceptibility genes. We therefore investigated the influence of STAT4 variants on the susceptibility and phenotype of inflammatory bowel diseases (IBD) in a large patient and control cohort.

Methodology/Principal Findings

Genomic DNA from 2704 individuals of Caucasian origin including 857 patients with Crohn's disease (CD), 464 patients with ulcerative colitis (UC), and 1383 healthy, unrelated controls was analyzed for seven SNPs in the STAT4 gene (rs11889341, rs7574865, rs7568275, rs8179673, rs10181656, rs7582694, rs10174238). In addition, a detailed genotype-phenotype analysis was performed. Our analysis revealed an association of the STAT4 SNP rs7574865 with overall decreased susceptibility to CD (p = 0.047, OR 0.86 [95% CI 0.74–0.99]). However, compared to CD patients carrying the wild type genotype, the STAT4 SNP rs7574865 was significantly associated with early CD onset (p = 0.021) and colonic CD (p = 0.008; OR = 4.60, 95% CI 1.63–12.96). For two other STAT4 variants, there was a trend towards protection against CD susceptibility (rs7568275, p = 0.058, OR 0.86 [95% CI 0.74–1.00]; rs10174238, p = 0.057, OR 0.86 [95% CI 0.75–1.00]). In contrast, we did not observe any association with UC susceptibility. Evidence for weak gene-gene interaction of STAT4 with the IL23R SNP rs11209026 was lost after Bonferroni correction.

Conclusions/Significance

Our results identified the STAT4 SNP rs7574865 as a disease-modifying gene variant in colonic CD. However, in contrast to SLE and RA, the effect of rs7574865 on CD susceptibility is only weak.

The cannabinoid 1 receptor (CNR1) 1359 G/A polymorphism modulates susceptibility to ulcerative colitis and the phenotype in Crohn's disease

BACKGROUND

Recent evidence suggests a crucial role of the endocannabinoid system, including the cannabinoid 1 receptor (CNR1), in intestinal inflammation. We therefore investigated the influence of the CNR1 1359 G/A (p.Thr453Thr; rs1049353) single nucleotide polymorphism (SNP) on disease susceptibility and phenotype in patients with ulcerative colitis (UC) and Crohn's disease (CD).

METHODS

Genomic DNA from 579 phenotypically well-characterized individuals was analyzed for the CNR1 1359 G/A SNP. Amongst these were 166 patients with UC, 216 patients with CD, and 197 healthy controls.

RESULTS

Compared to healthy controls, subjects A/A homozygous for the CNR1 1359 G/A SNP had a reduced risk to develop UC (p = 0.01, OR 0.30, 95% CI 0.12-0.78). The polymorphism did not modulate CD susceptibility, but carriers of the minor A allele had a lower body mass index than G/G wildtype carriers (p = 0.0005). In addition, homozygous carriers of the G allele were more likely to develop CD before 40 years of age (p = 5.9x10(-7)) than carriers of the A allele.

CONCLUSION

The CNR1 p.Thr453Thr polymorphism appears to modulate UC susceptibility and the CD phenotype. The endocannabinoid system may influence the manifestation of inflammatory bowel diseases, suggesting endocannabinoids as potential target for future therapies.

Paneth cell defensins and the regulation of the microbiome: détente at mucosal surfaces

Recently, our laboratory demonstrated that Paneth cell defensins, innate antimicrobial peptides that contribute to mucosal host defense, are able to regulate the composition of the intestinal bacterial microbiome. Using complementary mouse models of defensin deficiency (MMP7(-/-)) and surplus (HD5(+/+)), we noted defensin-dependent reciprocal shifts in the dominant bacterial species of the small intestine, without changes in total bacterial numbers. In addition, mice that expressed HD5 showed a significant loss of segemented filamentous bacteria (SFB), resulting in reduced numbers of Th17 cells in the lamina propria. This data showed a novel role for PC defensins in intestinal homeostasis, by regulation of the small intestinal microbiome. The microbiome plays an essential role in mediating host physiology, metabolism and immune response. The ability of PC defensins to regulate the composition of the biome suggests a much broader importance of these innate immune effectors than previously considered. In this addendum, the role of PC defensins in the regulation of the intestinal microbiome is reviewed, and discussed in the context of recent evidence that highlights the important role of PCs and defensins in the pathophysiology of inflammatory bowel disease.

Toll-like receptors (TLRs) and Nod-like receptors (NLRs) in inflammatory disorders

Toll-like receptors (TLRs) and Nod-like receptors (NLRs) are two major forms of innate immune sensors, which provide immediate responses against pathogenic invasion or tissue injury. Activation of these sensors induces the recruitment of innate immune cells such as macrophages and neutrophils, initiates tissue repair processes, and results in adaptive immune activation. Abnormalities in any of these innate sensor-mediated processes may cause excessive inflammation due to either hyper responsive innate immune signaling or sustained compensatory adaptive immune activation. Recent gene association studies appear to reveal strong associations of NLR gene mutations and development of several idiopathic inflammatory disorders. In contrast, TLR polymorphisms are less often associated with inflammatory disorders. Nevertheless, TLRs are up-regulated in the affected tissue of most inflammatory disorders, suggesting TLR signaling is involved in the pathogenesis of chronic and/or idiopathic inflammatory disorders. NLR signaling results in the formation of a molecular scaffold complex (termed an inflammasome) and orchestrates with TLRs to induce IL-1beta and IL-18, both of which are important mediators in the majority of inflammatory disorders. Therefore, understanding the roles of TLRs and NLRs in the pathogenesis of chronic and idiopathic inflammatory disorders may provide novel targets for the prevention and/or treatment of many common and uncommon diseases involving inflammation.

Role of Nod2 in the development of Crohn's disease

Crohn's Disease (CD) is caused by a loss of the regulatory capacity of the immune apparatus. Nod2 is an intracellular bacterial sensor and its mutations are associated with the development of CD. Here we summarize recent and controversial findings about the role of the Nod2 mutants in the disease process.

rs224136 on chromosome 10q21.1 and variants in PHOX2B, NCF4, and FAM92B are not major genetic risk factors for susceptibility to Crohn's disease in the German population

OBJECTIVES

Recently, a North American genome-wide association study identified three novel gene variants in PHOX2B, NCF4, and FAM92B as well as one single nucleotide polymorphisms (SNP; rs224136) in the intergenic region on chromosome 10q21.1 as being associated with Crohn's disease (CD). However, their influence on European CD patients as well as ulcerative colitis (UC) is unknown. Therefore we aimed to replicate these novel CD susceptibility variants in a large European cohort with inflammatory bowel disease and analyzed potential gene-gene interactions with variants in the NOD2/CARD15, IL23R, and ATG16L1 genes.

METHODS

Genomic DNA from 2,833 Caucasian individuals including 854 patients with CD, 476 patients with UC, and 1,503 healthy unrelated controls was analyzed for SNPs in PHOX2B (rs16853571), NCF4 (rs4821544), and FAM92B (rs8050910), including rs224136 on chromosome 10q21.1.

RESULTS

In our study population, no association of PHOX2B (P=0.563), NCF4 (P=0.506), FAM92B (P=0.401), and rs224136 (P=0.363) with CD was found. Similarly, none of these SNPs was associated with UC. In contrast, all analyzed SNPs in NOD2/CARD15, IL23R, and ATG16L1 were strongly associated with CD with P values ranging from 5.0x10(-3) to 1.6x10(-22), but there was no epistasis with polymorphisms in PHOX2B, NCF4, FAM92B, and rs224136.

CONCLUSIONS

In contrast to the North American population, PHOX2B, NCF4, FAM92B, and rs224136 are not associated with CD in the European population, whereas NOD2/CARD15, IL23R, and ATG16L1 are strongly associated with CD in both the North American and European populations, confirming these three genes as major CD susceptibility genes in Caucasian populations.

Correlation of magnetic resonance enteroclysis (MRE) and wireless capsule endoscopy (CE) in the diagnosis of small bowel lesions in Crohn's disease

BACKGROUND

The aim was to evaluate and compare the diagnostic performance of magnetic resonance enteroclysis (MRE) and wireless video capsule endoscopy (CE) in detecting and classifying small bowel Crohn's disease (CD) proximal to the terminal ileum.

METHODS

Nineteen patients with histologically proven CD (M:F = 13:6; mean 34 years, range 17-65) were prospectively included in the study when presenting with clinical signs suggesting stricturing or inflammatory lesions of CD in the proximal small bowel. All patients underwent MRE with an infusion technique and were then admitted to CE.

RESULTS

As for the presence or absence of pathology, results of MRE and CE were in total agreement for 44/52 (85%) evaluated segments. In judging lesion severity, MRE and CE yielded identical results in 29/52 (56%) segments. MRE underestimated pathology in 7/52 (14%) segments and revealed more severe pathology in 6/52 (12%) segments. CE identified subtle (n = 7) or severe (n = 2) mucosal pathology while MRE was normal. CE entirely missed severe inflammatory mural changes depicted in MRE in 1/52 (2%) segments.

CONCLUSIONS

MRE and CE show good correlation in the detection and localization of inflammatory bowel disease. As for disease activity, MRE is inferior in the detection of superficial mucosal disease but reliably discloses the presence of severe inflammatory changes within the bowel wall and beyond, which may be underestimated from the endoscopic aspect of the mucosal surface. MRE helps to rule out severe stenoses that should be referred for immediate surgical intervention. In conclusion, both modalities are complementary and MRE should be used in more severe cases of Crohn's disease and in patients who might have involvement beyond the mucosa of the small bowel.

NOD2/CARD15 genotype influences MDP-induced cytokine release and basal IL-12p40 levels in primary isolated peripheral blood monocytes

BACKGROUND

The functional link between mutations in NOD2 and Crohn's disease (CD) has not been entirely elucidated. The 1007fs mutation results in loss of NF-kappaB activation in response to muramyl dipeptide (MDP) but has also been linked to an increased IL-1beta processing and IL-12 release.

METHODS

We investigated the basal and MDP-triggered mRNA expression and protein release for TNF-alpha, IL-10, IL-1beta, and IL-12p40 in peripheral blood monocytes from 40 CD patients and 15 healthy individuals with different NOD2 genotypes.

RESULTS

Monocytes from individuals with 2 mutated NOD2 alleles (homozygous and compound-heterozygous individuals) displayed an impaired release of TNF-alpha and IL-10 but also of IL-1beta and IL-12p40 in response to MDP. In contrast to other NOD2 variants, the presence of at least 1 1007fs allele in double-mutated individuals completely abrogated NOD2 receptor function. Interestingly, monocytes from CD patients with 2 mutated NOD2 alleles displayed significantly higher basal levels of IL-12p40 in cell culture supernatants compared to wildtype CD patients and control individuals (P = 0.002 and P = 0.008, respectively). This was regardless of the IL23R genotype and was not mirrored by increased IL-12p40 plasma levels in these individuals.

CONCLUSIONS

The CD-associated NOD2 variants lead, in a dose- and mutation-dependent manner, to an impaired release of TNF-alpha, IL-10, IL-1beta, and IL-12p40 in response to MDP. The finding of increased basal levels for IL-12p40-related cytokines in monocytes with 2 mutated NOD2 alleles is likely to set a new link between NOD2 mutations and the inflammatory mechanisms underlying CD.

The ATG16L1 gene variants rs2241879 and rs2241880 (T300A) are strongly associated with susceptibility to Crohn's disease in the German population

OBJECTIVES

We analyzed ATG16L1, a recently identified Crohn's disease (CD) susceptibility gene, in a large cohort with inflammatory bowel disease (IBD) including potential interactions with other IBD genes as well as factors regulating its gene expression.

METHODS

Genomic DNA from 2,890 Caucasians including 768 patients with CD, 507 patients with ulcerative colitis (UC), and 1,615 healthy controls was analyzed for 9 different ATG16L1 single nucleotide polymorphisms (SNPs). Genotyping included CARD15/NOD2 variants p.Arg702Trp, p.Gly908Arg, and p.Leu1007fsX1008 and polymorphisms in SLC22A4/OCTN1 (1672 C-->T) and SLC22A5/OCTN2 (-207 G-->C) as well as 10 CD-associated IL23R variants. The transcriptional regulation of ATG16L1 was studied in intestinal epithelial cells following stimulation with Toll-like receptor (TLR) ligands and proinflammatory cytokines and in a murine ileitis model and CD biopsies.

RESULTS

All nine ATG16L1 gene variants analyzed displayed highly significant associations with CD demonstrating a CD-protective effect for the minor allele. The strongest associations were found for rs2241879 and the coding SNP rs2241880 (T300A); P= 3.6 x 10(-6) and 3.7 x 10(-6), respectively (OR 0.74, 95% CI 0.65-0.84 for both variants). The genotype-phenotype analysis revealed no significant associations. In UC, only rs6431660 was weakly disease-associated. There was no evidence for epistasis between the ATG16L1 gene and other susceptibility genes (IL23R, CARD15, SLC22A4/5). ATG16L1 mRNA expression was not upregulated in CD and murine ileitis, and was less than threefold increased in cells stimulated with proinflammatory cytokines and TLR ligands.

CONCLUSION

ATG16L1 is a CD susceptibility gene without epistatic interaction with other CD susceptibility genes and is not upregulated in intestinal inflammation.

Linking genetic susceptibility to Crohn's disease with Th17 cell function: IL-22 serum levels are increased in Crohn's disease and correlate with disease activity and IL23R genotype status

BACKGROUND

We analyzed the influence of Crohn's disease (CD)-associated IL23R gene variants on IL-22 that is expressed in IL-23R+ Th17 cells.

METHODS

IL-22 serum levels were measured in 242 CD patients and in 31 healthy controls. Subanalyses included serum levels of IL-6, TNF-alpha, IL-17A, IL-17F, C-reactive protein (CRP), and leukocyte count. In all patients, genotyping for 10 CD-associated IL23R single nucleotide polymorphisms (SNPs) and the 3 main CD-associated CARD15 variants was performed.

RESULTS

There was a highly significant increase in IL-22 serum expression in CD patients compared to healthy controls (P = 2.53 x 10(-9)). IL-22 serum levels correlated with disease activity: IL-22 levels in patients with a Crohn's disease activity index (CDAI) >150 were significantly higher than in patients with a CDAI <150 (P = 0.001), while TNF-alpha and IL-6 were not significantly different between these 2 groups. Analyzing the effect of 10 IL23R variants on IL-22 serum levels, we demonstrated that the quotients of mean IL-22 serum levels of carriers of the minor allele to the mean serum IL-22 in wildtype carriers correlated highly with the corresponding CD susceptibility risk for each gene variant (r = 0.807). The IL-22 levels in carriers of CD risk-increasing IL23R variants were significantly higher than in carriers of CD risk-decreasing IL23R variants (P = 0.008).

CONCLUSIONS

The Th17 cytokine IL-22 is expressed at high levels in CD and correlates with disease activity, offering a better separation between active and inactive CD than IL-6 and TNF-alpha. IL23R genotypes influence IL-22 serum expression, linking genetic CD susceptibility to Th17 cell function for the first time.

Genotype-phenotype analysis of the CXCL16 p.Ala181Val polymorphism in inflammatory bowel disease

To identify if genetic determinants of CXCL16 modulate the susceptibility and phenotype of inflammatory bowel diseases (IBD), we analyzed genomic DNA from 574 individuals (365 IBD patients, 209 healthy controls) for the CXCL16 p.Ala181Val polymorphism. In this study, we demonstrate that in Crohn's disease (CD), the CXCL16 p.Ala181Val polymorphism is not a disease susceptibility gene but associated with younger age at disease onset (p=0.016) and higher frequency of ileal involvement (p=0.024; OR 2.17; 95% CI 1.12-4.21) in ValVal carriers compared to a higher frequency of colonic involvement in AlaAla carriers (p=0.009; OR 2.60; CI 1.29-5.25). Carriers of at least one Val allele and one CARD15/NOD2 variant had a higher incidence of a stricturing and penetrating phenotype (p=0.030, OR 4.04, CI 1.27-12.84) and of stenoses (p=0.014; OR 3.97; CI 1.38-11.40) than patients carrying NOD2 variants only, suggesting that this polymorphism contributes to a severe disease phenotype in CD.