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

Interleukin-4 Gene Polymorphisms in Romanian Patients with Inflammatory Bowel Diseases: Association with Disease Risk and Clinical Features

1.

INTRODUCTION

Multiple cytokines have been studied for their role in the propagation of the inflammatory process related to inflammatory bowel diseases (IBD), but the role of interleukin-4 remains controversial. The aim of this study was to evaluate the role of two IL-4 gene single nucleotide polymorphisms (SNPs) in disease susceptibility and phenotypic expression. 2.

MATERIALS AND METHODS

A group of 160 patients with IBD (86CD/74UC) and 160 healthy controls were genotyped for IL-4 rs2243250/-590C/T and rs2070874/-34C/T using real-time polymerase chain reaction with TaqMan assay. 3.

RESULTS

The analysis of IBD patients and controls revealed a significantly reduced frequency of the minor allele T of both SNPs in CD patients (p = 0.03, OR 0.55 and p = 0.02, OR 0.52) and for the entire IBD group (p = 0.01, OR 0.57 and p = 0.01, OR 0.55). Haplotype analysis identified the most frequent haplotype (rs2243250/rs2070874 CC) associated with a high risk for developing IBD (either UC or CD) (p = 0.003). IBD patients with extraintestinal manifestations had significantly increased frequency of the minor alleles T. We also found an association between the presence of allele C of rs2070874 and response to antiTNF treatment. 4.

CONCLUSIONS

This is the first study to investigate the IL-4 gene's relation to IBD susceptibility conducted in Romania. Both SNPs were found to be associated with disease susceptibility and phenotypic features, such as extraintestinal manifestations and response to antiTNF agents.

MIF Variant rs755622 Is Associated with Severe Crohn's Disease and Better Response to Anti-TNF Adalimumab Therapy

Crohn's disease (CD), rheumatoid arthritis, psoriatic arthritis and other inflammatory diseases comprise a group of chronic diseases with immune-mediated pathogenesis which share common pathological pathways, as well as treatment strategies including anti-TNF biologic therapy. However, the response rate to anti-TNF therapy among those diseases varies, and approximately one third of patients do not respond. Since pharmacogenetic studies for anti-TNF therapy have been more frequent for other related diseases and are rare in CD, the aim of our study was to further explore markers associated with anti-TNF response in other inflammatory diseases in Slovenian CD patients treated with the anti-TNF drug adalimumab (ADA). We enrolled 102 CD patients on ADA, for which the response was defined after 4, 12, 20 and 30 weeks of treatment, using an IBDQ questionnaire and blood CRP value. We genotyped 41 SNPs significantly associated with response to anti-TNF treatment in other diseases. We found novel pharmacogenetic association between SNP rs755622 in the gene MIF (macrophage migration inhibitory factor) and SNP rs3740691 in the gene ARFGAP2 in CD patients treated with ADA. The strongest and most consistent association with treatment response was found for the variant rs2275913 in gene IL17A (p = 9.73 × 10-3).

Results of the Seventh Scientific Workshop of ECCO: Precision Medicine in IBD-What, Why, and How

Many diseases that affect modern humans fall in the category of complex diseases, thus called because they result from a combination of multiple aetiological and pathogenic factors. Regardless of the organ or system affected, complex diseases present major challenges in diagnosis, classification, and management. Current forms of therapy are usually applied in an indiscriminate fashion based on clinical information, but even the most advanced drugs only benefit a limited number of patients and to a variable and unpredictable degree. This 'one measure does not fit all' situation has spurred the notion that therapy for complex disease should be tailored to individual patients or groups of patients, giving rise to the notion of 'precision medicine' [PM]. Inflammatory bowel disease [IBD] is a prototypical complex disease where the need for PM has become increasingly clear. This prompted the European Crohn's and Colitis Organisation to focus the Seventh Scientific Workshop on this emerging theme. The articles in this special issue of the Journal address the various complementary aspects of PM in IBD, including what PM is; why it is needed and how it can be used; how PM can contribute to prediction and prevention of IBD; how IBD PM can aid in prognosis and improve response to therapy; and the challenges and future directions of PM in IBD. This first article of this series is structured on three simple concepts [what, why, and how] and addresses the definition of PM, discusses the rationale for the need of PM in IBD, and outlines the methodology required to implement PM in IBD in a correct and clinically meaningful way.

Activating Transcription Factor 6 Mediates Inflammatory Signals in Intestinal Epithelial Cells Upon Endoplasmic Reticulum Stress

BACKGROUND & AIMS

Excess and unresolved endoplasmic reticulum (ER) stress in intestinal epithelial cells (IECs) promotes intestinal inflammation. Activating transcription factor 6 (ATF6) is one of the signaling mediators of ER stress. We studied the pathways that regulate ATF6 and its role for inflammation in IECs.

METHODS

We performed an RNA interference screen, using 23,349 unique small interfering RNAs targeting 7783 genes and a luciferase reporter controlled by an ATF6-dependent ERSE (ER stress-response element) promoter, to identify proteins that activate or inhibit the ATF6 signaling pathway in HEK293 cells. To validate the screening results, intestinal epithelial cell lines (Caco-2 cells) were transfected with small interfering RNAs or with a plasmid overexpressing a constitutively active form of ATF6. Caco-2 cells with a CRISPR-mediated disruption of autophagy related 16 like 1 gene (ATG16L1) were used to study the effect of ATF6 on ER stress in autophagy-deficient cells. We also studied intestinal organoids derived from mice that overexpress constitutively active ATF6, from mice with deletion of the autophagy related 16 like 1 or X-Box binding protein 1 gene in IECs (Atg16l1^ΔIEC or Xbp1^ΔIEC, which both develop spontaneous ileitis), from patients with Crohn's disease (CD) and healthy individuals (controls). Cells and organoids were incubated with tunicamycin to induce ER stress and/or chemical inhibitors of newly identified activator proteins of ATF6 signaling, and analyzed by real-time polymerase chain reaction and immunoblots. Atg16l1^ΔIEC and control (Atg16l1^fl/fl) mice were given intraperitoneal injections of tunicamycin and were treated with chemical inhibitors of ATF6 activating proteins.

RESULTS

We identified and validated 15 suppressors and 7 activators of the ATF6 signaling pathway; activators included the regulatory subunit of casein kinase 2 (CSNK2B) and acyl-CoA synthetase long chain family member 1 (ACSL1). Knockdown or chemical inhibition of CSNK2B and ACSL1 in Caco-2 cells reduced activity of the ATF6-dependent ERSE reporter gene, diminished transcription of the ATF6 target genes HSP90B1 and HSPA5 and reduced NF-κB reporter gene activation on tunicamycin stimulation. Atg16l1^ΔIEC and or Xbp1^ΔIEC organoids showed increased expression of ATF6 and its target genes. Inhibitors of ACSL1 or CSNK2B prevented activation of ATF6 and reduced CXCL1 and tumor necrosis factor (TNF) expression in these organoids on induction of ER stress with tunicamycin. Injection of mice with inhibitors of ACSL1 or CSNK2B significantly reduced tunicamycin-mediated intestinal inflammation and IEC death and expression of CXCL1 and TNF in Atg16l1^ΔIEC mice. Purified ileal IECs from patients with CD had higher levels of ATF6, CSNK2B, and HSPA5 messenger RNAs than controls; early-passage organoids from patients with active CD show increased levels of activated ATF6 protein, incubation of these organoids with inhibitors of ACSL1 or CSNK2B reduced transcription of ATF6 target genes, including TNF.

CONCLUSIONS

Ileal IECs from patients with CD have higher levels of activated ATF6, which is regulated by CSNK2B and HSPA5. ATF6 increases expression of TNF and other inflammatory cytokines in response to ER stress in these cells and in organoids from Atg16l1^ΔIEC and Xbp1^ΔIEC mice. Strategies to inhibit the ATF6 signaling pathway might be developed for treatment of inflammatory bowel diseases.

Single Nucleotide Polymorphisms in Colitis-Associated Colorectal Cancer: A Current Overview with Emphasis on the Role of the Associated Genes Products

Colitis-Associated Colorectal Cancer (CA-CRC) is one of the most severe complications of Inflammatory Bowel Disease (IBD) and constitutes the cause of death in 10-15% of patients. The risk ratio for carcinogenesis depends on numerous factors, such as the extent of intestinal inflammatory lesions and the duration of the disease. CA-CRC is a major problem of today's gastroenterology and colorectal surgery due to the fact that the incidence and prevalence of IBD are increasing. In this review, we discussed the current state of knowledge regarding genetic differences between sporadic CRC and CA-CRC, especially pertaining to the chromosomal instability mechanism (CIN). In order to explain CA-CRC molecular basis, we have analyzed the data from studies regarding the correlations between CA-CRC and the presence of Single Nucleotide Polymorphisms (SNPs). Further focus on the role of associated proteins has emphasized the role of NF-κB signaling as the main link between inflammation and carcinogenesis during the course of IBD.

MicrobioLink: An Integrated Computational Pipeline to Infer Functional Effects of Microbiome-Host Interactions

Microbiome–host interactions play significant roles in health and in various diseases including autoimmune disorders. Uncovering these inter-kingdom cross-talks propels our understanding of disease pathogenesis and provides useful leads on potential therapeutic targets. Despite the biological significance of microbe–host interactions, there is a big gap in understanding the downstream effects of these interactions on host processes. Computational methods are expected to fill this gap by generating, integrating, and prioritizing predictions—as experimental detection remains challenging due to feasibility issues. Here, we present MicrobioLink, a computational pipeline to integrate predicted interactions between microbial and host proteins together with host molecular networks. Using the concept of network diffusion, MicrobioLink can analyse how microbial proteins in a certain context are influencing cellular processes by modulating gene or protein expression. We demonstrated the applicability of the pipeline using a case study. We used gut metaproteomic data from Crohn’s disease patients and healthy controls to uncover the mechanisms by which the microbial proteins can modulate host genes which belong to biological processes implicated in disease pathogenesis. MicrobioLink, which is agnostic of the microbial protein sources (bacterial, viral, etc.), is freely available on GitHub.

Impact of Genes and the Environment on the Pathogenesis and Disease Course of Inflammatory Bowel Disease

Crohn's disease and ulcerative colitis constitute two major subgroups of inflammatory bowel diseases (IBD), a group of complex polygenic diseases characterized by chronic and progressive inflammation in the gastrointestinal tract. In recent years, methodological advances in genetic analysis have greatly expanded our understanding of the genetic background of IBD. So far, more than 240 genetic risk loci have been identified for IBD. However, these risk alleles explain less than 30% of the susceptibility to disease development, suggesting that environmental factors contribute considerably. The increasing occurrence of IBD in Eastern countries following their 'westernization', as well as the increased risk of disease among those who migrate to high-incidence regions, also suggest that the environment is key in the pathogenesis of IBD. In this review, we summarize the current evidence on the role of genetic and environmental factors in the susceptibility to, and disease course of, IBD, and we suggest how these findings might be applied to clinical practice.

ATG16L1 orchestrates interleukin-22 signaling in the intestinal epithelium via cGAS-STING

A coding variant of the inflammatory bowel disease (IBD) risk gene ATG16L1 has been associated with defective autophagy and deregulation of endoplasmic reticulum (ER) function. IL-22 is a barrier protective cytokine by inducing regeneration and antimicrobial responses in the intestinal mucosa. We show that ATG16L1 critically orchestrates IL-22 signaling in the intestinal epithelium. IL-22 stimulation physiologically leads to transient ER stress and subsequent activation of STING-dependent type I interferon (IFN-I) signaling, which is augmented in Atg16l1 ΔIEC intestinal organoids. IFN-I signals amplify epithelial TNF production downstream of IL-22 and contribute to necroptotic cell death. In vivo, IL-22 treatment in Atg16l1 ΔIEC and Atg16l1 ΔIEC/Xbp1 ΔIEC mice potentiates endogenous ileal inflammation and causes widespread necroptotic epithelial cell death. Therapeutic blockade of IFN-I signaling ameliorates IL-22-induced ileal inflammation in Atg16l1 ΔIEC mice. Our data demonstrate an unexpected role of ATG16L1 in coordinating the outcome of IL-22 signaling in the intestinal epithelium.

Interleukin-4 and Interleukin-10 Gene Polymorphisms in Patients with Inflammatory Bowel Disease

BACKGROUND

Changes in cytokine expression have been frequently found in patients with inflammatory bowel disease (IBD). Cytokine values outside the normal range may be somewhat related to common polymorphisms within cytokine genes.

OBJECTIVE

The present study was designed to investigate the possible association between polymorphisms within Interleukin IL-4 and IL-10 genes and susceptibility to and clinical features of IBD.

METHODS

The study population was composed of 140 healthy controls and 75 patients with IBD (40 patients with Crohn's disease (CD) and 35 patients with ulcerative colitis (UC)). Genotyping was performed using polymerase chain reaction with sequence-specific primers.

RESULTS

Higher frequencies for the C allele of IL-4-590 polymorphism (P < 0.0001; odds ratio [OR], 5.68; 95% confidence interval [95% CI], 3.28-9.83) and for the T allele of IL-4-1098 polymorphism (P = 0.016; OR, 1.83; 95% CI, 1.11-3.02) were observed in the whole group of IBD patients. The IL-4-590 C allele was also significantly overrepresented when IBD patients were subdivided into CD and UC (P < 0.0001; OR, 5.2-6.28). While the IL-4-1098 T allele was present at higher frequencies in patients with UC (P = 0.05; OR, 1.95), but not in CD (P = 0.09). Multiple pairwise comparisons indicated that genotypes of all polymorphisms investigated within IL-4 gene are correlated with IBD, CD, and UC. Haplotype analysis showed that the IL-4-1098/-590 TC haplotype might predispose individuals to IBD, CD, and UC whereas the IL-4-1098/-590 TT and GC haplotypes have a protective effect. On the contrary, neither allele nor genotype frequencies of IL-10 polymorphisms (IL-10-1082 A > G, IL-10-592 A > C, and IL-10-819 T > C) were associated with IBD, CD, or UC.

CONCLUSIONS

The present study suggests that IL-4 polymorphisms might play a role in susceptibility to IBD and its major subtypes in the Iranian population.

Among autophagy genes, ATG16L1 but not IRGM is associated with Crohn's disease in Iranians

BACKGROUND

The prevalence of inflammatory bowel diseases is uprising in countries like Iran. Genetic predisposing elements play prominent role in the pathogenesis of Crohn's disease. In this study we studied the role of autophagy genes like IRGM (Immunity related GTPase M) and ATG16L1 (Autophagy related 16 like 1) in the pathogenesis of Crohn's Disease in Iranian patients.

METHODS

One hundred thirty-eight patients and 99 normal controls were recruited in this study. Polymorphisms in -1644 and -308 upstream of IRGM gene were studied by PCR-sequencing and 20 kb CNVdel/insertion was studied by specific PCR. Rs10065171, rs4958847 in IRGM gene and rs2241880 in ATG16L1 were studied by Taqman genotyping assays.

RESULTS

None of the so-called predisposing alleles of IRGM gene predispose Iranians to Crohn's disease while the prevalence of some of them like CNV deletion was higher in normal controls. Surprisingly all the so-called predisposing alleles in IRGM were linked to each other (especially rs4958847 with rs10065172 and polymorphisms in -308 region with rs4958847). Patients harboring A allele in rs4958847 site showed higher ratio of fibrostenotic type of disease while in patients with C/T genotype in rs4958847, colonic involvement was seen more frequently. G allele in ATG16L1 was associated with Crohn's disease though it was not associated with any phenotypic manifestation.

CONCLUSION

In our study the association of ATG16L1 to Crohn's disease in Iranian patients was confirmed while it was shown that the studied polymorphisms in IRGM was not associated with Crohn's disease. Therefore in order to have a better picture about the genetics of Crohn's disease in Iranian patients, it is recommended to study other clinically effective polymorphisms in IRGM and ATG16L1 in addition to other genes which are responsible for the process of autophagy.

Genetic variants in cellular transport do not affect mesalamine response in ulcerative colitis

Background and aims

Mesalamine is commonly used to treat ulcerative colitis (UC). Although mesalamine acts topically, in vitro data suggest that intracellular transport is required for its beneficial effect. Genetic variants in mucosal transport proteins may affect this uptake, but the clinical relevance of these variants has not been studied. The aim of this study was to determine whether variants in genes involved in cellular transport affect the response to mesalamine in UC.

Methods

Subjects with UC from a 6-week clinical trial using multiple doses of mesalamine were genotyped using a genome-wide array that included common exome variants. Analysis focused on cellular transport gene variants with a minor allele frequency >5%. Mesalamine response was defined as improvement in Week 6 Physician’s Global Assessment (PGA) and non-response as a lack of improvement in Week 6 PGA. Quality control thresholds included an individual genotyping rate of >90%, SNP genotyping rate of >98%, and exclusion for subjects with cryptic relatedness. All included variants met Hardy-Weinberg equilibrium (p>0.001).

Results

457 adults with UC were included with 280 responders and 177 non-responders. There were no common variants in transporter genes that were associated with response to mesalamine. The genetic risk score of responders was similar to that of non-responders (p = 0.18). Genome-wide variants demonstrating a trend towards mesalamine response included ST8SIA5 (p = 1x10^-5).

Conclusions

Common transporter gene variants did not affect response to mesalamine in adult UC. The response to mesalamine may be due to rare genetic events or environmental factors such as the intestinal microbiome.

Associations between single-nucleotide polymorphisms and inflammatory bowel disease-associated colorectal cancers in inflammatory bowel disease patients: a meta-analysis

PURPOSE

To assess the correlation between single-nucleotide polymorphisms (SNPs) and inflammatory bowel disease (IBD)-associated colorectal cancer (CRC) in IBD patients.

METHODS

A systematic search of PubMed, EmBase, and Cochrane databases was performed. Five genetic models (allelic, dominant, recessive, heterozygous and homozygous models) were used to analyze the associations, and trial sequential analysis was used to analyze the robustness of the results.

RESULTS

We collected and analyzed the results of seven trials including a total of 2287 patients in our meta-analysis. A total of 8 SNPs were tested in IBD patients. For rs1800629 of TNF-α, the allelic model showed that polymorphism at this locus significantly increased the risk of IBD-associated CRC in IBD patients (OR 4.45, 95% CI 3.18-6.21, P < 0.001). The results also showed a significant association between rs1800629 and an IBD-associated CRC population (heterozygous model: OR 4.335, 95% CI 2.329-8.069, P < 0.001; homozygous model: OR 11.5, 95% CI 2.498-52.592, P = 0.002; dominant model: OR 4.986, 95% CI 2.754-9.026, P < 0.001; recessive model: OR 7.208, 95% CI 1.588-32.72, P = 0.01). Other studies have found that mutation of rs1143627 of IL1B (allelic model: OR 2.97; 95% CI 1.74-5.05, P < 0.001) and rs1050152 of OCTN1 (allelic model: OR 1.637, 95% CI 1.078-2.485, P = 0.021) increased the proportion of IBD-associated CRC in the population. Moreover, there were significant associations between IBD-associated CRC and ITLN rs2274910, gene desert rs1551398 and rs4871611, FCGR2A rs1801274, and S100-Z rs7712957 in the allelic model.

CONCLUSION

Associations between SNPs and the proportion of IBD-associated CRC in IBD patients were examined, and further investigation of additional SNPs and their association with the risk of morbidity is needed.

Meta-Analysis of Risk Association Between Interleukin-17A and F Gene Polymorphisms and Inflammatory Diseases

This meta-analysis examined the relationship between IL-17A (rs2275913) and IL17F (rs763780 T/C) gene polymorphisms and the risk of inflammatory diseases, including periodontitis, rheumatoid arthritis (RA), and inflammatory bowel disease. PubMed, MEDLINE, EMBASE, Web of Science, and Elsevier Science Direct were searched, and odds ratios (ORs) with 95% confidence interval (CI) were calculated to estimate the strength of the association. A total of 25 studies comprising 7,474 cases and 10,628 controls were included. Significant associations were found between inflammatory diseases and IL-17A rs2275913 A versus G allele (OR = 1.197, P = 0.033) and the GA versus GG genotype in the codominant model (OR = 1.406, P = 0.036). Our findings suggested that individuals who carry the rs2275913 A allele or GA genotype have a 20% or 41%-increased risk of inflammatory diseases compared with subjects with the G allele or GG genotype, respectively. With respect to IL-17F rs763780, the C versus T allele (OR = 1.94; P = 0.040), the TC versus TT (OR = 1.39; P = 0.041), the CC versus TT (OR = 2.71; P = 0.003), as well as the TC + CC versus TT genotype (OR = 1.83; P = 0.032) were risk factors for RA. In summary, our pooled analysis indicated that the IL-17A (rs2275913) and IL17F (rs763780 T/C) increased the RA risk.

Paneth Cell Alterations in the Development and Phenotype of Crohn's Disease

Pathogenesis of Crohn's disease (CD) involves immune and microbial dysregulation, induced by environmental factors in genetically susceptible individuals. There are believed to be multiple subtypes of CD, which contributes to its observed clinical heterogeneity. This concept has been reinforced by recognition of the complexity of the genetic, microbial, immune, and environmental factors that affect risk for CD. Paneth cells mediate immunity and maintain the small intestinal epithelium; defects in activities of these cells have been observed in high proportions of patients with CD, and are associated with a more aggressive CD phenotype. Paneth cells integrate complex genetic, immune, and environmental signals, therefore alterations in their function could lead to different subtypes of CD, as observed in studies in cohorts of primarily European descent. Subtypes of CD associated with Paneth cell function have been observed even among patients from different genetic backgrounds. We discuss genetic susceptibility loci for CD and how these affect Paneth cell activity.

Genetic polymorphism in ATG16L1 gene influences the response to adalimumab in Crohn's disease patients

AIM

To see if SNPs could help predict response to biological therapy using adalimumab (ADA) in Crohn's disease (CD).

MATERIALS & METHODS

IBDQ index and CRP levels were used to monitor therapy response. We genotyped 31 CD-associated genes in 102 Slovenian CD patients.

RESULTS

The strongest association for treatment response defined as decrease in CRP levels was found for ATG16L1 SNP rs10210302. Additional SNPs in 7 out of 31 tested CD-associated genes (PTGER4, CASP9, IL27, C11orf30, CCNY, IL13, NR1I2) showed suggestive association with ADA response.

CONCLUSION

Our results suggest ADA response in CD patients is genetically predisposed by SNPs in CD risk genes and suggest ATG16L1 as most promising candidate gene for drug response in ADA treatment. Original submitted 24 September 2014; Revision submitted 1 December 2014.

Role of HLA typing on Crohn's disease pathogenesis

Crohn's disease (CD) is the main type of chronic inflammatory bowel disease of unknown etiology. Evidence from family and twin studies suggests that genetics plays a significant role in predisposing an individual to develop Crohn's disease. A susceptibility locus for Crohn's disease has been mapped 3 to chromosome 16: a frameshift variant and two missense variants of NOD2, encoding a member of the Apaf-1/Ced-4 superfamily of apoptosis regulators which is expressed in hematopoietic compartment cells and intestinal epithelial cells as well as in paneth cells, where NOD2 may play an important role in the pathogenesis of Crohn disease in the gastrointestinal system. This leads to alteration the structure of either the leucine-rich repeat domain of the protein or the adjacent region. NOD2 activates nuclear factor NF-kB; this activating function is regulated by the carboxy-terminal leucine-rich repeat domain, which has two functions, first an inhibitory role and also acts as an intracellular receptor for components of microbial pathogens. Thus, NOD2 gene product confers susceptibility to Crohn's disease by altering the recognition of these components and/or by over-activating NF-kB in intestinal epithelial cells as well as in paneth cells. Further confirmation of a genetic predisposition comes from studies of the association between the human leukocyte antigen (HLA) system and CD. The immunogenetic predisposition may be considered an important requirement for the development of CD, as several alleles of human major histocompatibility complex had an association with CD. Although it is difficult to estimate the importance of this region in determining overall genetic susceptibility in a population, studies of HLA allele sharing within families suggest that this region contributes between 10% and 33% of the total genetic risk of Crohn's disease.

The use of prognostic factors in inflammatory bowel diseases

The disease spectrum and natural course of Crohn's disease and ulcerative colitis are highly variable. The majority of Crohn's disease patients will require surgery at a certain stage in their disease compared to only a fraction of the ulcerative colitis patients. Similarly, some patients are destined to experience an indolent disease course while others will require early intensive therapy. Ideally, these subtypes of patients should be identified as early as possible with the help of reliable prognostic factors in order to guide personalized therapeutic decisions. In this review, the authors focused on the most relevant reports on the use of different prognostic factors to predict disease course, postoperative recurrence and response to therapy in patients with inflammatory bowel disease. The last 15 years have seen a wealth of novel genetic and serological markers of disease severity. Nevertheless, none of these markers have proven to be superior to careful clinical phenotyping and endoscopic features early in the disease course. Future attempts should apply an integrated approach that unites clinical, serological and (epi)genetic information with environmental influences, with a clear focus on the microbiome to ultimately identify molecular-based and clinically relevant subgroups.

Very early-onset inflammatory bowel disease: gaining insight through focused discovery

The pathogenesis of pediatric inflammatory bowel disease (IBD) is only partially understood. Strong evidence implicates a strong genetic component including high monozygotic twin concordance and familial disease phenotype concordance rates. Genome-wide association studies have identified associations between >160 genetic loci and the risk for developing IBD. The roles of implicated genes are largely immune-mediated, although other functions include cellular migration, oxidative stress, and carbohydrate metabolism. Additionally, growing literature describes monogenic causes of IBD that frequently present as infantile or very early-onset IBD. The interplay between IBD risk single nucleotide polymorphisms and rare genetic variants has yet to be determined. Studying patients with very early-onset IBD may elicit genetic factors that could be applied to broader populations of IBD. This review describes what is known about the genetic causes of very early-onset IBD and genetic strategies that may unravel more of the genetic causes of IBD.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Identification of risk loci for Crohn's disease phenotypes using a genome-wide association study

BACKGROUND & AIMS

Crohn's disease is a highly heterogeneous inflammatory bowel disease comprising multiple clinical phenotypes. Genome-wide association studies (GWASs) have associated a large number of loci with disease risk but have not associated any specific genetic variants with clinical phenotypes. We performed a GWAS of clinical phenotypes in Crohn's disease.

METHODS

We genotyped 576,818 single-nucleotide polymorphisms in a well-characterized cohort of 1090 Crohn's disease patients of European ancestry. We assessed their association with 17 phenotypes of Crohn's disease (based on disease location, disease behavior, disease course, age at onset, and extraintestinal manifestations). A total of 57 markers with strong associations to Crohn's disease phenotypes (P < 2 × 10(-4)) were subsequently analyzed in an independent replication cohort of 1296 patients of European ancestry.

RESULTS

We replicated the association of 4 loci with different Crohn's disease phenotypes. Variants in MAGI1, CLCA2, 2q24.1, and LY75 loci were associated with a complicated stricturing disease course (Pcombined = 2.01 × 10(-8)), disease location (Pcombined = 1.3 × 10(-6)), mild disease course (Pcombined = 5.94 × 10(-7)), and erythema nodosum (Pcombined = 2.27 × 10(-6)), respectively.

CONCLUSIONS

In a GWAS, we associated 4 loci with clinical phenotypes of Crohn's disease. These findings indicate a genetic basis for the clinical heterogeneity observed for this inflammatory bowel disease.

IBD candidate genes and intestinal barrier regulation

Technological advances in the large scale analysis of human genetics have generated profound insights into possible genetic contributions to chronic diseases including the inflammatory bowel diseases (IBDs), Crohn's disease and ulcerative colitis. To date, 163 distinct genetic risk loci have been associated with either Crohn's disease or ulcerative colitis, with a substantial degree of genetic overlap between these 2 conditions. Although many risk variants show a reproducible correlation with disease, individual gene associations only affect a subset of patients, and the functional contribution(s) of these risk variants to the onset of IBD is largely undetermined. Although studies in twins have demonstrated that the development of IBD is not mediated solely by genetic risk, it is nevertheless important to elucidate the functional consequences of risk variants for gene function in relevant cell types known to regulate key physiological processes that are compromised in IBD. This article will discuss IBD candidate genes that are known to be, or are suspected of being, involved in regulating the intestinal epithelial barrier and several of the physiological processes presided over by this dynamic and versatile layer of cells. This will include assembly and regulation of tight junctions, cell adhesion and polarity, mucus and glycoprotein regulation, bacterial sensing, membrane transport, epithelial differentiation, and restitution.

Infliximab therapy increases the frequency of circulating CD16(+) monocytes and modifies macrophage cytokine response to bacterial infection

Crohn's disease (CD) has been correlated with altered macrophage response to microorganisms. Considering the efficacy of infliximab treatment on CD remission, we investigated infliximab effects on circulating monocyte subsets and on macrophage cytokine response to bacteria. Human peripheral blood monocyte-derived macrophages were obtained from CD patients, treated or not with infliximab. Macrophages were infected with Escherichia coli, Enterococcus faecalis, Mycobacterium avium subsp. paratuberculosis (MAP) or M. avium subsp avium, and cytokine levels [tumour necrosis factor (TNF) and interleukin (IL)-10] were evaluated at different time-points. To evaluate infliximab-dependent effects on monocyte subsets, we studied CD14 and CD16 expression by peripheral blood monocytes before and after different infliximab administrations. We also investigated TNF secretion by macrophages obtained from CD16(+) and CD16(-) monocytes and the frequency of TNF(+) cells among CD16(+) and CD16(-) monocyte-derived macrophages from CD patients. Infliximab treatment resulted in elevated TNF and IL-10 macrophage response to bacteria. An infliximab-dependent increase in the frequency of circulating CD16(+) monocytes (particularly the CD14(++) CD16(+) subset) was also observed (before infliximab: 4·65 ± 0·58%; after three administrations: 10·68 ± 2·23%). In response to MAP infection, macrophages obtained from CD16(+) monocytes were higher TNF producers and CD16(+) macrophages from infliximab-treated CD patients showed increased frequency of TNF(+) cells. In conclusion, infliximab treatment increased the TNF production of CD macrophages in response to bacteria, which seemed to depend upon enrichment of CD16(+) circulating monocytes, particularly of the CD14(++) CD16(+) subset. Infliximab treatment of CD patients also resulted in increased macrophage IL-10 production in response to bacteria, suggesting an infliximab-induced shift to M2 macrophages.

Cell death and inflammatory bowel diseases: apoptosis, necrosis, and autophagy in the intestinal epithelium

Cell death mechanisms have been associated with the development of inflammatory bowel diseases in humans and mice. Recent studies suggested that a complex crosstalk between autophagy/apoptosis, microbe sensing, and enhanced endoplasmic reticulum stress in the epithelium could play a critical role in these diseases. In addition, necroptosis, a relatively novel programmed necrosis-like pathway associated with TNF receptor activation, seems to be also present in the pathogenesis of Crohn's disease and in specific animal models for intestinal inflammation. This review attempts to cover new data related to cell death mechanisms and inflammatory bowel diseases.

Genetic susceptibility and genotype-phenotype association in 588 Danish children with inflammatory bowel disease

AIM

To investigate the association between known inflammatory bowel disease (IBD)-associated genetic variants and development of paediatric IBD, and specific clinical sub-phenotypes.

MATERIAL AND METHODS

In this case-control study we included IBD patients <18 years of age at diagnosis from the Danish National Patient Registry and healthy children <18 years of age were randomly selected from the Danish Central Office of Civil Registration. The latter had filled out a questionnaire regarding health status, and DNA was obtained from blood samples and the buccal mucosa. Patient files were retrieved and clinical information was extracted. DNA was obtained from Guthrie cards from the Danish National Neonatal Screening Biobank (PKU-biobanken) at Statens Serum Institut and from blood samples.

RESULTS

A total of 588 IBD patients (244 Crohn's disease (CD), 318 ulcerative colitis (UC) and 26 IBD-unclassified (IBDU)) and 543 healthy controls were included. We found an association between CD and rs22411880 (ATG16L1, odds ratio (OR)=1.7 [1.1-1.7], p=0.003), rs5743289 (NOD2, OR=1.4 [1.1-1.9], p=0.009) and the paediatric specific rs1250550 (ZMIZ1, OR=0.7 [0.5-0.9], p=0.01). None of the investigated 41 SNPs were associated with disease localisation, medical treatment or surgery after correcting for multiple analyses.

CONCLUSION

We found an association between CD and three previously published genetic variants and replicated the association with the paediatric specific ZMIZ1 gene. No Bonferroni corrected significant genotype-phenotype associations were found. For future studies aimed at finding predictors for disease course in (paediatric) IBD, it will be worthwhile to include a combination of genetic, clinical and serological markers.

NOD-like receptors in intestinal homeostasis and epithelial tissue repair

The intestinal epithelium constitutes a dynamic physical barrier segregating the luminal content from the underlying mucosal tissue. Following injury, the epithelial integrity is restored by rapid migration of intestinal epithelial cells (IECs) across the denuded area in a process known as wound healing. Hence, through a sequence of events involving restitution, proliferation and differentiation of IECs the gap is resealed and homeostasis reestablished. Relapsing damage followed by healing of the inflamed mucosa is a hallmark of several intestinal disorders including inflammatory bowel diseases (IBD). While several regulatory peptides, growth factors and cytokines stimulate restitution of the epithelial layer after injury, recent evidence in the field underscores the contribution of innate immunity in controlling this process. In particular, nucleotide-binding and oligomerization domain-like receptors (NLRs) play critical roles in sensing the commensal microbiota, maintaining homeostasis, and regulating intestinal inflammation. Here, we review the process of intestinal epithelial tissue repair and we specifically focus on the impact of NLR-mediated signaling mechanisms involved in governing epithelial wound healing during disease.

IRGM rs13361189 polymorphism may contribute to susceptibility to Crohn's disease: A meta-analysis

The aim of the present meta-analysis was to evaluate the correlation between a common polymorphism, rs13361189 C>T in the immunity-related GTPase M (IRGM) gene, and susceptibility to Crohn's disease (CD). The PubMed, CISCOM, CINAHL, Web of Science, Google Scholar, EBSCO, Cochrane Library and CBM databases were investigated from database inception through to October 1, 2013 without the application of any language restrictions. The meta-analysis was performed using STATA 12.0 software and the relative risk (RR) with a 95% confidence interval (CI) was calculated. Seven case-control studies were included with a total of 3,093 CD patients and 3,227 healthy control subjects. The results of the meta-analysis revealed that the IRGM rs13361189 polymorphism correlates with an increased risk of CD (T allele versus C allele: RR=1.25 with 95% CI, 1.04-1.50; P=0.016 and CT + TT versus CC: RR=1.21 with 95% CI, 1.03-1.42; P=0.018). A subgroup analysis conducted using a genotyping method indicated that the IRGM rs13361189 polymorphism was correlated with an increased risk of CD in the TaqMan^® (T allele versus C allele: RR=1.32 with 95% CI, 1.01-1.73; P=0.042) and the polymerase chain reaction-restriction fragment length polymorphism subgroups (T allele versus C allele: RR=1.80 with 95% CI, 1.32-2.45; P<0.001 and CT + TT versus CC: RR=1.61 with 95% CI, 1.19-2.18; P=0.018). However, no correlation was observed in the direct sequencing subgroup (P>0.05). Further subgroup analysis by sample size demonstrated significant correlations between the IRGM rs13361189 polymorphism and an increased risk of CD in the large sample-size subgroup (T allele versus C allele: RR=1.46 with 95% CI, 1.26-1.68; P<0.001 and CT + TT versus CC: RR=1.40 with 95% CI, 1.21-1.62; P<0.001). However, no correlation was identified between the IRGM rs13361189 polymorphism and CD risk in the small sample-size subgroup (P>0.05). The present meta-analysis indicated that the IRGM rs13361189 polymorphism may contribute to susceptibility to CD. Thus, IRGM rs13361189 polymorphism may be a potential biomarker for the early diagnosis of CD.

Clinical and genetic factors predicting response to therapy in patients with Crohn's disease

AIM

To identify clinical and/or genetic predictors of response to several therapies in Crohn's disease (CD) patients.

METHODS

We included 242 patients with CD (133 females) aged (mean ± standard deviation) 39 ± 12 years and a disease duration of 12 ± 8 years. The single-nucleotide polymorphisms (SNPs) studied were ABCB1 C3435T and G2677T/A, IL23R G1142A, C2370A, and G9T, CASP9 C93T, Fas G670A and LgC844T, and ATG16L1 A898G. Genotyping was performed with real-time PCR with Taqman probes.

RESULTS

Older patients responded better to 5-aminosalicylic acid (5-ASA) and to azathioprine (OR 1.07, p = 0.003 and OR 1.03, p = 0.01, respectively) while younger ones responded better to biologicals (OR 0.95, p = 0.06). Previous surgery negatively influenced response to 5-ASA compounds (OR 0.25, p = 0.05), but favoured response to azathioprine (OR 2.1, p = 0.04). In respect to genetic predictors, we observed that heterozygotes for ATGL16L1 SNP had a significantly higher chance of responding to corticosteroids (OR 2.51, p = 0.04), while homozygotes for Casp9 C93T SNP had a lower chance of responding both to corticosteroids and to azathioprine (OR 0.23, p = 0.03 and OR 0.08, p = 0.02,). TT carriers of ABCB1 C3435T SNP had a higher chance of responding to azathioprine (OR 2.38, p = 0.01), while carriers of ABCB1 G2677T/A SNP, as well as responding better to azathioprine (OR 1.89, p = 0.07), had a lower chance of responding to biologicals (OR 0.31, p = 0.07), which became significant after adjusting for gender (OR 0.75, p = 0.005).

CONCLUSIONS

In the present study, we were able to identify a number of clinical and genetic predictors of response to several therapies which may become of potential utility in clinical practice. These are preliminary results that need to be replicated in future pharmacogenomic studies.

Association between variants of the autophagy related gene--IRGM and susceptibility to Crohn's disease and ulcerative colitis: a meta-analysis

Background

Polymorphisms in immunity-related GTPase family M (IRGM) gene may be associated with inflammatory bowel disease (IBD) by affecting autophagy. However, the genetic association studies on three common variants in IRGM gene (rs13361189, rs4958847 and rs10065172) have shown inconsistent results.

Methodology/ Principal Findings

The PubMed and Embase were searched up to June 5, 2013 for studies on the association between three IRGM polymorphisms and IBD risk. Data were extracted and the odd ratios (ORs) and 95% confidence intervals (95% CIs) were calculated. Finally, we performed a meta-analysis of 25 eligible studies in 3 SNPs located at IRGM gene by using a total of 20590 IBD cases and 27670 controls. The analysis showed modest significant association for the rs13361189, rs4958847 and rs10065172 variants in Crohn’s disease (CD): the risk estimates for the allele contrast were OR=1.306 (1.200-1.420), p=5.2×10^-10, OR=1.182 (1.082-1.290), p=0.0002, and OR=1.248 (1.057-1.473), p=0.009 respectively (still significant when the p value was Bonferroni adjusted to 0.017). When stratified by ethnicity, significantly increased CD risk was observed in Europeans, but not in Asians. Conversely, there was no association of rs13361189 or rs4958847 variant with risk of ulcerative colitis (UC).

Conclusions/ Significance

These results indicated that autophagy gene-IRGM polymorphisms appear to confer susceptibility to CD but not UC, especially in Europeans. Our data may provide further understanding of the role of autophagy in the pathogenesis of CD.

Recent insights on the putative role of autophagy in autoimmune diseases

The incidence of autoimmune pathologies is increasing worldwide. This has stimulated interest on their etiopathogenesis, caused by a complex interaction of genetic and environmental factors. With the advent of genome-wide linkage, candidate gene and genome wide association studies, risk polymorphisms in autophagy-related genes were discovered in several autoimmune conditions suggesting the possible contribution of autophagy to their etiopathogenesis. Autophagy represents the principal catabolic process mediated by lysosomes used by eukaryotic cells and is strictly regulated by proteins belonging to the Atg family. The function of autophagy has been well characterized in various tissues and systems, but its role in the regulation of innate and adaptive immune systems has been only recently discovered. It plays a fundamental role in the modulation of thymocyte selection and in the generation of T lymphocyte repertoire by participating in the intracellular antigen presentation on MHC class-II molecules by thymic epithelial cells. Furthermore, the generation of mice with knockout for specific autophagy-related genes induced several immunological alterations, including defects in B and T cell compartments and in T cell activation. In this review we report recent evidence on the role of autophagy in autoimmunity and discuss its relevance to the pathogenesis of these diseases. We finally highlight that future research may disclose potential new therapeutic targets for the treatment of this category of disorders by modulating the autophagic pathway.

Personalizing therapy for inflammatory bowel diseases

Inflammatory bowel diseases (IBDs; e.g., Crohn's disease [CD] and ulcerative colitis [UC]) are chronic immunologically mediated diseases characterized by frequent relapses, often requiring hospitalization and surgery. There is substantial heterogeneity in the progressive natural history of disease with cumulative accrual of bowel damage and impairment of functioning. Recent advances in therapeutics have significantly improved our ability to achieve disease remission; yet therapies remain expensive and are associated with significant side effects precluding widespread use in all patients with IBD. Consequently, algorithms for the management of patients with IBD require a personalized approach incorporating an individual's projected likely natural history, the probability of response to a specific therapeutic agent and an informed approach to management of loss of response to current therapies.

How does genotype influence disease phenotype in inflammatory bowel disease?

Inflammatory bowel diseases (Crohn's disease and ulcerative colitis) are chronic immunologically mediated diseases of the gut. Advances in genetics have revolutionized our understanding of the pathogenesis of these conditions with 163 risk loci identified, encompassing a variety of immunologic functions. There is substantial heterogeneity in the natural history of these diseases with respect to disease onset, course, and progression to complications. There are also significant variations in response to therapies and susceptibility to therapy-related and disease-related complications. An important need in the field is to identify predictors of disease course, complications, and likelihood of response and adverse events to allow for targeted therapeutic decision making. The genotype of an individual in constant and non-modifiable, and thus could potentially fulfill the role of important predictors of these outcomes. In this review, we discuss the existing literature on the prediction of various disease phenotypes in Crohn's disease and ulcerative colitis using underlying genotype. We also identify gaps in the literature and suggest future directions for research. There is need for large, multi-institutional, and international collaborative consortia with efficient and detailed cohort accrual, phenotypic definition, genotyping, and dynamic assessments of external (e.g., diet) and internal (microbiome) environment to allow us to progress toward personalized and precision medicine in the management of these complex diseases.

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.

The role of autophagy in Crohn's disease

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