Characterization of genetic loci that affect susceptibility to inflammatory bowel diseases in African Americans

Mendelian randomization study of inflammatory bowel disease and type 1 diabetes

PURPOSE

Our purpose was to investigate and test the causal relationship between type 1 diabetes (T1D) and inflammatory bowel disease (IBD) and its major phenotypes, including ulcerative colitis (UC) and Crohn's disease (CD), in two large datasets.

METHODS

We obtained IBD samples from the largest publicly available genome-wide association study (GWAS), as well as the FinnGen database and the publicly accessible IEU GWAS database of T1D. We employed a two-sample Mendelian randomization approach to assess bidirectional causality using the inverse variance weighting (IVW) method as the primary outcome.

RESULTS

Genetic predisposition to T1D was associated with reduced risk of IBD (IVW: odds ratio (OR), 0.867; 95% confidence interval (CI), [0.852, 0.883]; P < 0.001), UC (OR = 0.879 [0.823, 0.939], P < 0.001), and CD (OR = 0.925 [0.872, 0.981], P = 0.009). The republication results found IBD genetically possessed negative association with T1D (OR = 0.781 [0.684, 0.891], P < 0.001). Additionally, a meta-analysis of results was conducted to prove the strong evidence between T1D and CD (OR = 0.95 [0.91, 0.98]; p = 0.01).

CONCLUSIONS

This study first demonstrated a causal effect of TID on the reduced risk of CD in the mendelian randomization study.

Metabolic health and genetic predisposition in inflammatory bowel disease: Insights from a prospective cohort study

BACKGROUND

Metabolic disorders exhibit strong inflammatory underpinnings and vice versa. This study aimed to investigate the association between metabolic health status, genetic predisposition, and the risk of inflammatory bowel disease (IBD), and to explore the potential benefits of maintaining ideal metabolic status for individuals with a predetermined genetic risk of IBD.

METHOD

This population-based prospective study included 385,820 unrelated European descent participants from the UK Biobank. Using multivariable Cox regression, we assessed the relationship of metabolic phenotypes with risk of IBD and its subtypes. We also developed a polygenic risk score to examine how metabolic health status interacted with genetic risk in relation to IBD risk.

RESULTS

During the follow-up period of 4,328,895 person-years, 2,044 newly-diagnosed IBD cases were identified. Higher genetic risk and an increasing number of abnormal metabolic phenotypes were associated with elevated IBD risk (p-trend <0.001). Individuals with high genetic risk and poor metabolic health had a significantly higher risk of IBD (HR=4.56, 95 % CI=3.27-6.36) compared to those with low genetic risk and ideal metabolic health. These results remained consistent for IBD subtypes. Maintaining ideal metabolic status reduced IBD risk within each genetic risk category and jointly decreased subsequent risk by 40 % in high genetic risk individuals.

CONCLUSION

Our study reveals a combined impact of poor metabolic health and genetic risk on IBD incidence. Those with low genetic risk and optimal metabolic health exhibit the lowest IBD risk, offering insights into potential management strategies for individuals at predefined genetic risk.

Impact of prenatal and postnatal maternal IBD status on offspring's risk of IBD: a population-based cohort study

OBJECTIVE

In utero exposure to maternal inflammation may impact immune system development and subsequent risk of disease. We investigated whether a maternal diagnosis of IBD before childbirth is linked to a higher risk of IBD in offspring compared with a diagnosis after childbirth. Further, we analysed paternal IBD status for comparison.

DESIGN

Using Danish health registers, we identified all individuals born in Denmark between 1997 and 2022 and their legal parents, as well as their IBD status. Cox proportional hazards regression analyses adjusted for calendar period and mode of delivery were used to estimate offspring IBD risk by maternal and paternal IBD status before and after childbirth.

RESULTS

Of 1 290 358 children, 10 041 (0.8%) had mothers with IBD diagnosis before childbirth and 9985 (0.8%) had mothers with IBD diagnosis after childbirth. Over 18 370 420 person-years, 3537 individuals were diagnosed with IBD. Offspring of mothers with IBD before childbirth had an adjusted HR of IBD of 6.27 (95% CI 5.21, 7.54) compared with those without maternal IBD, while offspring of mothers with IBD after childbirth had an adjusted HR of 3.88 (95% CI 3.27, 4.60). Corresponding adjusted HRs were 5.26 (95% CI 4.22, 6.56) among offspring with paternal IBD before childbirth and 3.73 (95% CI 3.10, 4.50) for paternal IBD after childbirth.

CONCLUSION

Offspring had a greater risk of IBD when either parent was diagnosed before childbirth rather than later, emphasising genetic predisposition and environmental risk factors rather than maternal inflammation in utero as risk factors for IBD.

Transcriptome-wide association studies associated with Crohn's disease: challenges and perspectives

Crohn's disease (CD) is regarded as a lifelong progressive disease affecting all segments of the intestinal tract and multiple organs. Based on genome-wide association studies (GWAS) and gene expression data, transcriptome-wide association studies (TWAS) can help identify susceptibility genes associated with pathogenesis and disease behavior. In this review, we overview seven reported TWASs of CD, summarize their study designs, and discuss the key methods and steps used in TWAS, which affect the prioritization of susceptibility genes. This article summarized the screening of tissue-specific susceptibility genes for CD, and discussed the reported potential pathological mechanisms of overlapping susceptibility genes related to CD in a certain tissue type. We observed that ileal lipid-related metabolism and colonic extracellular vesicles may be involved in the pathogenesis of CD by performing GO pathway enrichment analysis for susceptibility genes. We further pointed the low reproducibility of TWAS associated with CD and discussed the reasons for these issues, strategies for solving them. In the future, more TWAS are needed to be designed into large-scale, unified cohorts, unified analysis pipelines, and fully classified databases of expression trait loci.

Differential Manifestations of Inflammatory Bowel Disease Based on Race and Immigration Status

BACKGROUND AND AIMS

The prevalence of inflammatory bowel disease (IBD) is increasing globally. In this context, identifying risk factors for severe disease is important. We examined how race/ethnicity and immigration status influence IBD manifestations, treatments, and outcomes in a diverse, tertiary-care safety-net hospital.

METHODS

We conducted a single-center retrospective review of all IBD inpatients and outpatients treated from 1997-2017. Using logistic regression modeling, we compared disease onset, treatment, and outcomes by race (White, Black, Hispanic, or Asian) and immigration status (US-born vs foreign-born).

RESULTS

A total of 577 patients were identified, of which 29.8% were White, 27.4% were Hispanic, 21.7% were Black, and 13.0% were Asian. Compared to Whites, Asians were more likely to be male (odds ratio [OR] 2.63, 95% confidence interval [CI]: 1.45, 5.00), whereas Blacks were more likely to be diagnosed with Crohn's disease (OR 1.75, 95% CI: 1.10, 2.77) and more likely to undergo IBD-related intestinal resection (OR 2.49, 95% CI: 1.40, 4.50). Compared to US-born patients, foreign-born patients were more likely to be diagnosed with ulcerative colitis (OR 1.77, 95% CI: 1.04, 3.02). They were also less likely to be diagnosed before 16 years of age (OR 0.19, 95% CI: 0.08, 0.41), to have undergone intestinal resections (OR 0.39, 95% CI: 0.19, 0.83), to have received biologics (OR 0.43, 95% CI: 0.25, 0.76), or to have had dermatologic manifestations (OR 0.12, 95% CI: 0.03, 0.41).

CONCLUSION

IBD phenotype varies by race, although foreign-born patients of all races show evidence of later-onset and milder disease. These findings may aid in disease prognostication and clinical management and, furthermore, may provide insight into intrinsic and environmental influences on IBD pathogenesis.

multi-GPA-Tree: Statistical approach for pleiotropy informed and functional annotation tree guided prioritization of GWAS results

Genome-wide association studies (GWAS) have successfully identified over two hundred thousand genotype-trait associations. Yet some challenges remain. First, complex traits are often associated with many single nucleotide polymorphisms (SNPs), most with small or moderate effect sizes, making them difficult to detect. Second, many complex traits share a common genetic basis due to 'pleiotropy' and and though few methods consider it, leveraging pleiotropy can improve statistical power to detect genotype-trait associations with weaker effect sizes. Third, currently available statistical methods are limited in explaining the functional mechanisms through which genetic variants are associated with specific or multiple traits. We propose multi-GPA-Tree to address these challenges. The multi-GPA-Tree approach can identify risk SNPs associated with single as well as multiple traits while also identifying the combinations of functional annotations that can explain the mechanisms through which risk-associated SNPs are linked with the traits. First, we implemented simulation studies to evaluate the proposed multi-GPA-Tree method and compared its performance with existing statistical approaches. The results indicate that multi-GPA-Tree outperforms existing statistical approaches in detecting risk-associated SNPs for multiple traits. Second, we applied multi-GPA-Tree to a systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA), and to a Crohn's disease (CD) and ulcertive colitis (UC) GWAS, and functional annotation data including GenoSkyline and GenoSkylinePlus. Our results demonstrate that multi-GPA-Tree can be a powerful tool that improves association mapping while facilitating understanding of the underlying genetic architecture of complex traits and potential mechanisms linking risk-associated SNPs with complex traits.

Differentiating gastrointestinal tuberculosis and Crohn's disease- a comprehensive review

Gastrointestinal Tuberculosis (GITB) and Crohn's disease (CD) are both chronic granulomatous diseases with a predilection to involve primarily the terminal ileum. GITB is often considered a disease of the developing world, while CD and inflammatory bowel disease are considered a disease of the developed world. But in recent times, the epidemiology of both diseases has changed. Differentiating GITB from CD is of immense clinical importance as the management of both diseases differs. While GITB needs anti-tubercular therapy (ATT), CD needs immunosuppressive therapy. Misdiagnosis or a delay in diagnosis can lead to catastrophic consequences. Most of the clinical features, endoscopic findings, and imaging features are not pathognomonic for either of these two conditions. The definitive diagnosis of GITB can be clinched only in a fraction of cases with microbiological positivity (acid-fast bacilli, mycobacterial culture, or PCR-based tests). In most cases, the diagnosis is often based on consistent clinical, endoscopic, imaging, and histological findings. Similarly, no single finding can conclusively diagnose CD. Multiparametric-based predictive models incorporating clinical, endoscopy findings, histology, radiology, and serology have been used to differentiate GITB from CD with varied results. However, it is limited by the lack of validation studies for most such models. Many patients, especially in TB endemic regions, are initiated on a trial of ATT to see for an objective response to therapy. Early mucosal response assessed at two months is an objective marker of response to ATT. Prolonged ATT in CD is recognized to have a fibrotic effect. Therefore, early discrimination may be vital in preventing the delay in the diagnosis of CD and avoiding a complicated course.

IL-12 and IL-23 pathway inhibition in inflammatory bowel disease

Interleukin-12 (IL-12) and interleukin-23 (IL-23), which belong to the IL-12 family of cytokines, have a key role in intestinal homeostasis and inflammation and are implicated in the pathogenesis of inflammatory bowel disease. Upon their secretion by antigen-presenting cells, they exert both pro-inflammatory and anti-inflammatory receptor-mediated effects. An increased understanding of these biological effects, particularly the pro-inflammatory effects mediated by IL-12 and IL-23, has led to the development of monoclonal antibodies that target a subunit common to IL-12 and IL-23 (p40; targeted by ustekinumab and briakinumab), or the IL-23-specific subunit (p19; targeted by risankizumab, guselkumab, brazikumab and mirikizumab). This Review provides a summary of the biology of the IL-12 family cytokines IL-12 and IL-23, discusses the role of these cytokines in intestinal homeostasis and inflammation, and highlights IL-12- and IL-23-directed drug development for the treatment of Crohn's disease and ulcerative colitis.

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

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

Trans-ancestry, Bayesian meta-analysis discovers 20 novel risk loci for inflammatory bowel disease in an African American, East Asian and European cohort

Inflammatory bowel disease (IBD) is an immune-mediated chronic intestinal disorder with major phenotypes: ulcerative colitis (UC) and Crohn's disease (CD). Multiple studies have identified over 240 IBD susceptibility loci. However, most studies have centered on European (EUR) and East Asian (EAS) populations. The prevalence of IBD in non-EUR, including African Americans (AAs), has risen in recent years. Here we present the first attempt to identify loci in AAs using a trans-ancestry Bayesian approach (MANTRA) accounting for heterogeneity between diverse ancestries while allowing for the similarity between closely related populations. We meta-analyzed genome-wide association studies (GWAS) and Immunochip data from a 2015 EUR meta-analysis of 38 155 IBD cases and 48 485 controls and EAS Immunochip study of 2824 IBD cases and 3719 controls, and our recent AA IBD GWAS of 2345 cases and 5002 controls. Across the major IBD phenotypes, we found significant evidence for 92% of 205 loci lead SNPs from the 2015 meta-analysis, but also for three IBD loci only established in latter studies. We detected 20 novel loci, all containing immunity-related genes or genes with other evidence for IBD or immune-mediated disease relevance: PLEKHG5;TNFSFR25 (encoding death receptor 3, receptor for TNFSF15 gene product TL1A), XKR6, ELMO1, BC021024;PI4KB;PSMD4 and APLP1 for IBD; AUTS2, XKR6, OSER1, TET2;AK094561, BCAP29 and APLP1 for CD; and GABBR1;MOG, DQ570892, SPDEF;ILRUN, SMARCE1;CCR7;KRT222;KRT24;KRT25, ANKS1A;TCP11, IL7, LRRC18;WDFY4, XKR6 and TNFSF4 for UC. Our study highlights the value of combining low-powered genomic studies from understudied populations of diverse ancestral backgrounds together with a high-powered study to enable novel locus discovery, including potentially important therapeutic IBD gene targets.

3DFAACTS-SNP: using regulatory T cell-specific epigenomics data to uncover candidate mechanisms of type 1 diabetes (T1D) risk

Background

Genome-wide association studies (GWAS) have enabled the discovery of single nucleotide polymorphisms (SNPs) that are significantly associated with many autoimmune diseases including type 1 diabetes (T1D). However, many of the identified variants lie in non-coding regions, limiting the identification of mechanisms that contribute to autoimmune disease progression. To address this problem, we developed a variant filtering workflow called 3DFAACTS-SNP to link genetic variants to target genes in a cell-specific manner. Here, we use 3DFAACTS-SNP to identify candidate SNPs and target genes associated with the loss of immune tolerance in regulatory T cells (Treg) in T1D.

Results

Using 3DFAACTS-SNP, we identified from a list of 1228 previously fine-mapped variants, 36 SNPs with plausible Treg-specific mechanisms of action. The integration of cell type-specific chromosome conformation capture data in 3DFAACTS-SNP identified 266 regulatory regions and 47 candidate target genes that interact with these variant-containing regions in Treg cells. We further demonstrated the utility of the workflow by applying it to three other SNP autoimmune datasets, identifying 16 Treg-centric candidate variants and 60 interacting genes. Finally, we demonstrate the broad utility of 3DFAACTS-SNP for functional annotation of all known common (> 10% allele frequency) variants from the Genome Aggregation Database (gnomAD). We identified 9376 candidate variants and 4968 candidate target genes, generating a list of potential sites for future T1D or other autoimmune disease research.

Conclusions

We demonstrate that it is possible to further prioritise variants that contribute to T1D based on regulatory function, and illustrate the power of using cell type-specific multi-omics datasets to determine disease mechanisms. Our workflow can be customised to any cell type for which the individual datasets for functional annotation have been generated, giving broad applicability and utility.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13072-022-00456-5.

Role of Bile Acids and Nuclear Receptors in Acupuncture in Improving Crohn's Disease

Nuclear receptors (NRs) are ligand-dependent transcription factors that regulate the transcription of target genes. Bile acids (BAs) can be used as effector molecules to regulate physiological processes in the gut, and NRs are important receptors for bile acid signaling. Relevant studies have shown that NRs are closely related to the occurrence of Crohn's disease (CD). Although the mechanism of NRs in CD has not been clarified completely, growing evidence shows that NRs play an important role in regulating intestinal immunity, mucosal barrier, and intestinal flora. NRs can participate in the progress of CD by mediating inflammation, immunity, and autophagy. As the important parts of traditional Chinese medicine (TCM) therapy, acupuncture and moxibustion in the treatment of CD curative mechanism can get a lot of research support. At the same time, acupuncture and moxibustion can regulate the changes of related NRs. Therefore, to explore whether acupuncture can regulate BA circulation and NRs expression and then participate in the disease progression of CD, a new theoretical basis for acupuncture treatment of CD is provided.

One genome, many cell states: epigenetic control of innate immunity

A hallmark of the innate immune system is its ability to rapidly initiate short-lived or sustained transcriptional programs in a cell-specific and pathogen-specific manner that is dependent on dynamic chromatin states. Much of the epigenetic landscape is set during cellular differentiation; however, pathogens and other environmental cues also induce changes in chromatin that can either promote tolerance or 'train' innate immune cells for amplified secondary responses. We review chromatin processes that enable innate immune cell differentiation and functional transcriptional responses in naive or experienced cells, in concert with signal transduction and cellular metabolic shifts. We discuss how immune chromatin mechanisms are maladapted in disease and novel therapeutic approaches for cellular reprogramming.

Epigenetic regulation of 5α reductase-1 underlies adaptive plasticity of reproductive function and pubertal timing

Background

Women facing increased energetic demands in childhood commonly have altered adult ovarian activity and shorter reproductive lifespan, possibly comprising a strategy to optimize reproductive success. Here, we sought to understand the mechanisms of early-life programming of reproductive function, by integrating analysis of reproductive tissues in an appropriate mouse model with methylation analysis of proxy tissue DNA in a well-characterized population of Bangladeshi migrants in the UK. Bangladeshi women whose childhood was in Bangladesh were found to have later pubertal onset and lower age-matched ovarian reserve than Bangladeshi women who grew-up in England. Subsequently, we aimed to explore the potential relevance to the altered reproductive phenotype of one of the genes that emerged from the screens.

Results

Of the genes associated with differential methylation in the Bangladeshi women whose childhood was in Bangladesh as compared to Bangladeshi women who grew up in the UK, 13 correlated with altered expression of the orthologous gene in the mouse model ovaries. These mice had delayed pubertal onset and a smaller ovarian reserve compared to controls. The most relevant of these genes for reproductive function appeared to be SRD5A1, which encodes the steroidogenic enzyme 5α reductase-1. SRD5A1 was more methylated at the same transcriptional enhancer in mice ovaries as in the women’s buccal DNA, and its expression was lower in the hypothalamus of the mice as well, suggesting a possible role in the central control of reproduction. The expression of Kiss1 and Gnrh was also lower in these mice compared to controls, and inhibition of 5α reductase-1 reduced Kiss1 and Gnrh mRNA levels and blocked GnRH release in GnRH neuronal cell cultures. Crucially, we show that inhibition of this enzyme in female mice in vivo delayed pubertal onset.

Conclusions

SRD5A1/5α reductase-1 responds epigenetically to the environment and its downregulation appears to alter the reproductive phenotype. These findings help to explain diversity in reproductive characteristics and how they are shaped by early-life environment and reveal novel pathways that might be targeted to mitigate health issues caused by life-history trade-offs.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12915-021-01219-6.

Epigenetic Regulation of Cannabinoid-Mediated Attenuation of Inflammation and Its Impact on the Use of Cannabinoids to Treat Autoimmune Diseases

Chronic inflammation is considered to be a silent killer because it is the underlying cause of a wide range of clinical disorders, from cardiovascular to neurological diseases, and from cancer to obesity. In addition, there are over 80 different types of debilitating autoimmune diseases for which there are no cure. Currently, the drugs that are available to suppress chronic inflammation are either ineffective or overtly suppress the inflammation, thereby causing increased susceptibility to infections and cancer. Thus, the development of a new class of drugs that can suppress chronic inflammation is imperative. Cannabinoids are a group of compounds produced in the body (endocannabinoids) or found in cannabis (phytocannabinoids) that act through cannabinoid receptors and various other receptors expressed widely in the brain and immune system. In the last decade, cannabinoids have been well established experimentally to mediate anti-inflammatory properties. Research has shown that they suppress inflammation through multiple pathways, including apoptosis and inducing immunosuppressive T regulatory cells (Tregs) and myeloid-derived suppressor cells (MDSCs). Interestingly, cannabinoids also mediate epigenetic alterations in genes that regulate inflammation. In the current review, we highlight how the epigenetic modulations caused by cannabinoids lead to the suppression of inflammation and help identify novel pathways that can be used to target autoimmune diseases.

Potassium bromate (KBrO3) modulates oxidative stress and inflammatory biomarkers in sodium hydroxide (NaOH) - induced Crohn's colitis in Wistar rats

Potassium bromate (KBrO₃) present in consumed ozonised water was recently documented to exacerbate experimental gastric ulcer. Information, however, is vague as regards its effects in the colon where water reabsorption occurs. In this study, we observed the possible effects of KBrO₃ on oxidative stress and inflammatory biomarkers in sodium hydroxide (NaOH) - induced Crohn's colitis (CC). Wistar rats (180-200 g) were divided into six groups (n = 10): (i) control; (ii) untreated CC (induced by 1.4% NaOH; intra-rectal administration); and (iii-vi) CC treated with vitamin E, KBrO₃, vitamin E+KBrO₃, and sulphazalazine, respectively, for 7 days. Body weight and stool score were monitored daily. By day 3 and 7, excised colon was evaluated for ulcer scores and biochemical and histological analysis. Blood samples collected on days 3 and 7 were assayed for haematological indices using standard methods. Data were subjected to analysis of variance (ANOVA) and p ≤ 0.05 considered significant. Platelet/lymphocyte ratio, colonic ulcer score, malondialdehyde, and mast cells were significantly decreased while colonic sulfhydryl, and Ca²⁺- and Na⁺/K⁺-ATPase activities were increased following KBrO₃ treatment compared with untreated CC. These findings suggest that KBrO₃ may mitigate against NaOH-induced CC via inhibiting mast cell population and oxidative and inflammatory content but stimulating colonic sulfhydryl and Ca²⁺- and Na⁺/K⁺-ATPase activities.

Transethnic analysis of the human leukocyte antigen region for ulcerative colitis reveals not only shared but also ethnicity-specific disease associations

Inflammatory bowel disease (IBD) is a chronic inflammatory disease of the gut. Genetic association studies have identified the highly variable human leukocyte antigen (HLA) region as the strongest susceptibility locus for IBD and specifically DRB1*01:03 as a determining factor for ulcerative colitis (UC). However, for most of the association signal such as delineation could not be made because of tight structures of linkage disequilibrium within the HLA. The aim of this study was therefore to further characterize the HLA signal using a transethnic approach. We performed a comprehensive fine mapping of single HLA alleles in UC in a cohort of 9272 individuals with African American, East Asian, Puerto Rican, Indian and Iranian descent and 40 691 previously analyzed Caucasians, additionally analyzing whole HLA haplotypes. We computationally characterized the binding of associated HLA alleles to human self-peptides and analyzed the physicochemical properties of the HLA proteins and predicted self-peptidomes. Highlighting alleles of the HLA-DRB1*15 group and their correlated HLA-DQ-DR haplotypes, we not only identified consistent associations (regarding effects directions/magnitudes) across different ethnicities but also identified population-specific signals (regarding differences in allele frequencies). We observed that DRB1*01:03 is mostly present in individuals of Western European descent and hardly present in non-Caucasian individuals. We found peptides predicted to bind to risk HLA alleles to be rich in positively charged amino acids. We conclude that the HLA plays an important role for UC susceptibility across different ethnicities. This research further implicates specific features of peptides that are predicted to bind risk and protective HLA proteins.

Effects of Race and Ethnicity on Diagnosis and Management of Inflammatory Bowel Diseases

Although Crohn's disease (CD) and ulcerative colitis (UC) have been considered as disorders that affect individuals of European ancestry, the epidemiology of the inflammatory bowel diseases (IBDs) is changing. Coupled with the increasing incidence of IBD in previously low-incidence areas, the population demographics of IBD in the United States are also changing, with increases among non-White races and ethnicities. It is therefore important to fully understand the epidemiology and progression of IBD in different racial and ethnic groups, and the effects of race and ethnicity on access to care, use of resources, and disease-related outcomes. We review differences in IBD development and progression among patients of different races and ethnicities, discussing the effects of factors such as access to care, delays in diagnosis, and health and disease perception on disparities in IBD care and outcomes. We identify research priorities for improving health equity among minority patients with IBD.

Differential regulation of JAK/STAT-signaling in patients with ulcerative colitis and Crohn’s disease

In 2018, the pan-Janus kinase (JAK) inhibitor tofacitinib was launched for the treatment of ulcerative colitis (UC). Although tofacitinib has proven efficacious in patients with active UC, it failed in patients with Crohn’s disease (CD). This finding strongly hints at a different contribution of JAK signaling in both entities. Here, we review the current knowledge on the interplay between the JAK/signal transducer and activator of transcription (STAT) pathway and inflammatory bowel diseases (IBD). In particular, we provide a detailed overview of the differences and similarities of JAK/STAT-signaling in UC and CD, highlight the impact of the JAK/STAT pathway in experimental colitis models and summarize the published evidence on JAK/STAT-signaling in immune cells of IBD as well as the genetic association between the JAK/STAT pathway and IBD. Finally, we describe novel treatment strategies targeting JAK/STAT inhibition in UC and CD and comment on the limitations and challenges of the new drug class.

Construction and benchmarking of a multi-ethnic reference panel for the imputation of HLA class I and II alleles

Genotype imputation of the human leukocyte antigen (HLA) region is a cost-effective means to infer classical HLA alleles from inexpensive and dense SNP array data. In the research setting, imputation helps avoid costs for wet lab-based HLA typing and thus renders association analyses of the HLA in large cohorts feasible. Yet, most HLA imputation reference panels target Caucasian ethnicities and multi-ethnic panels are scarce. We compiled a high-quality multi-ethnic reference panel based on genotypes measured with Illumina’s Immunochip genotyping array and HLA types established using a high-resolution next generation sequencing approach. Our reference panel includes more than 1,300 samples from Germany, Malta, China, India, Iran, Japan and Korea and samples of African American ancestry for all classical HLA class I and II alleles including HLA-DRB3/4/5. Applying extensive cross-validation, we benchmarked the imputation using the HLA imputation tool HIBAG, our multi-ethnic reference and an independent, previously published data set compiled of subpopulations of the 1000 Genomes project. We achieved average imputation accuracies higher than 0.924 for the commonly studied HLA-A, -B, -C, -DQB1 and -DRB1 genes across all ethnicities. We investigated allele-specific imputation challenges in regard to geographic origin of the samples using sensitivity and specificity measurements as well as allele frequencies and identified HLA alleles that are challenging to impute for each of the populations separately. In conclusion, our new multi-ethnic reference data set allows for high resolution HLA imputation of genotypes at all classical HLA class I and II genes including the HLA-DRB3/4/5 loci based on diverse ancestry populations.

Functions and regulation of T cell-derived interleukin-10

Interleukin (IL)-10 is an essential anti-inflammatory cytokine and functions as a negative regulator of immune responses to microbial antigens. IL-10 is particularly important in maintaining the intestinal microbe-immune homeostasis. Loss of IL-10 promotes the development of inflammatory bowel disease (IBD) as a consequence of an excessive immune response to the gut microbiota. IL-10 also functions more generally to prevent excessive inflammation during the course of infection. Although IL-10 can be produced by virtually all cells of the innate and adaptive immune system, T cells constitute a non-redundant source for IL-10 in many cases. The various roles of T cell-derived IL-10 will be discussed in this review. Given that IL-10 is at the center of maintaining the delicate balance between effective immunity and tissue protection, it is not surprising that IL-10 expression is highly dynamic and tightly regulated. We summarize the environmental signals and molecular pathways that regulate IL-10 expression. While numerous studies have provided us with a deep understanding of IL-10 biology, the majority of findings have been made in murine models, prompting us to highlight gaps in our knowledge about T cell-derived IL-10 in the human system.

What did we learn from multiple omics studies in asthma?

More than a decade has passed since the finalization of the Human Genome Project. Omics technologies made a huge leap from trendy and very expensive to routinely executed and relatively cheap assays. Simultaneously, we understood that omics is not a panacea for every problem in the area of human health and personalized medicine. Whilst in some areas of research omics showed immediate results, in other fields, including asthma, it only allowed us to identify the incredibly complicated molecular processes. Along with their possibilities, omics technologies also bring many issues connected to sample collection, analyses and interpretation. It is often impossible to separate the intrinsic imperfection of omics from asthma heterogeneity. Still, many insights and directions from applied omics were acquired-presumable phenotypic clusters of patients, plausible biomarkers and potential pathways involved. Omics technologies develop rapidly, bringing improvements also to asthma research. These improvements, together with our growing understanding of asthma subphenotypes and underlying cellular processes, will likely play a role in asthma management strategies.

Review article: the genetics of the human leucocyte antigen region in inflammatory bowel disease

BACKGROUND

The human leucocyte antigen (HLA) complex, located at chromosome 6p21.3 is a highly polymorphic region containing the classical class I and II HLA genes. The region is highly associated with inflammatory bowel disease (IBD), largely through genome-wide association studies (GWAS).

AIMS

To review the role of HLA in immune function, summarise data on risk/protective HLA genotypes for IBD, discuss the role of HLA in IBD pathogenesis, treatment and examine limitations that might be addressed by future research.

METHODS

An organised search strategy was used to collate articles describing HLA genes in IBD, including Crohn's disease and ulcerative colitis.

RESULTS

All classical HLA genes with variation (including HLA-A, B, C, DRB1, DQA1, DQB1, DPA1 and DPB1) harbour IBD-associated genotypes. The most implicated gene is HLA-DRB1, with HLA-DRB1*03:01 the most associated risk allele in both Crohn's disease and ulcerative colitis. Elucidating precise disease associations is challenging due to high linkage disequilibrium between HLA genotypes. The mechanisms by which risk alleles cause disease are multifactorial, with the best evidence indicating structural and electrostatic alteration impacting antigen binding and downstream signalling. Adverse medication events have been associated with HLA genotypes including with thiopurines (pancreatitis) and anti-TNF agents (antibody formation).

CONCLUSIONS

The HLA complex is associated with multiple risk/protective alleles for IBD. Future research utilising long-read technology, ascertainment of zygosity and integration in disease modelling will improve the functional understanding and clinical translation of genetic findings.

Systems biology in inflammatory bowel diseases: on the way to precision medicine

Inflammatory bowel diseases (IBD) are chronic and recurrent inflammatory disorders of the gastrointestinal tract. The elucidation of their etiopathology requires complex and multiple approaches. Systems biology has come to fulfill this need in approaching the pathogenetic mechanisms of IBD and its etiopathology, in a comprehensive way, by combining data from different scientific sources. In combination with bioinformatics and network medicine, it uses principles from computer science, mathematics, physics, chemistry, biology, medicine and computational tools to achieve its purposes. Systems biology utilizes scientific sources that provide data from omics studies (e.g., genomics, transcriptomics, etc.) and clinical observations, whose combined analysis leads to network formation and ultimately to a more integrative image of disease etiopathogenesis. In this review, we analyze the current literature on the methods and the tools utilized by systems biology in order to cover an innovative and exciting field: IBD-omics.

Constitutive STAT5 activation regulates Paneth and Paneth-like cells to control Clostridium difficile colitis

Clostridium difficile impairs Paneth cells, driving intestinal inflammation that exaggerates colitis. Besides secreting bactericidal products to restrain C. difficile, Paneth cells act as guardians that constitute a niche for intestinal epithelial stem cell (IESC) regeneration. However, how IESCs are sustained to specify Paneth-like cells as their niche remains unclear. Cytokine-JAK-STATs are required for IESC regeneration. We investigated how constitutive STAT5 activation (Ca-pYSTAT5) restricts IESC differentiation towards niche cells to restrain C. difficile infection. We generated inducible transgenic mice and organoids to determine the effects of Ca-pYSTAT5-induced IESC lineages on C. difficile colitis. We found that STAT5 absence reduced Paneth cells and predisposed mice to C. difficile ileocolitis. In contrast, Ca-pYSTAT5 enhanced Paneth cell lineage tracing and restricted Lgr5 IESC differentiation towards pYSTAT5+Lgr5-CD24+Lyso+ or cKit+ niche cells, which imprinted Lgr5hiKi67+ IESCs. Mechanistically, pYSTAT5 activated Wnt/β-catenin signaling to determine Paneth cell fate. In conclusion, Ca-pYSTAT5 gradients control niche differentiation. Lack of pYSTAT5 reduces the niche cells to sustain IESC regeneration and induces C. difficile ileocolitis. STAT5 may be a transcription factor that regulates Paneth cells to maintain niche regeneration.

Inhibition of LINC00994 represses malignant behaviors of pancreatic cancer cells: interacting with miR-765-3p/RUNX2 axis

Pancreatic cancer exhibits one of the worst prognosis of all human cancers, and it is associated with gene dysregulation. Our microarray results first indicated long intergenic non-protein coding RNA 994 (LINC00994) as an upregulated long non-coding RNA (lncRNA) and miR-765-3p as a downregulated microRNA (miRNA) in pancreatic cancer tissues (Fold change ≥ 2 and P < 0.05; three paired samples). To investigate the role of LINC00994 in pancreatic carcinogenesis, a pair of short hairpin RNA (shRNA) was used to stably knock down the endogenous expression of LINC00994 in Panc-1 and AsPC-1 pancreatic cancer cells in vitro. We found that LINC00994 silencing inhibited the growth, migration and invasion, and promoted the G1 cell cycle arrest and apoptosis in Panc-1 and AsPC-1 cells. Furthermore, the expression of LINC00994 was negatively correlated with that of miR-765-3p in 10 pancreatic cancer specimens. Runt-related transcription factor 2 (RUNX2), a molecule that contributes to the aggressive behaviors of pancreatic cancer, was herein verified as a novel target for miR-765-3p. Like LINC00994, its expression was elevated in pancreatic cancers. Silencing of LINC00994 and RUNX2 reduced each other's expression in both Panc-1 and AsPC-1 cells. RUNX2 3'UTR and LINC00994 competed to bind miR-765-3p. Additionally, LINC00994-silenced cells regained their aggressive behaviors when miR-765-3p was antagonized, which was accompanied with RUNX2 re-expression. Collectively, our study reveals that LINC00994 contributes to the malignant behaviors of pancreatic cancer cells by preventing miR-765-3p from targeting RUNX2. LINC00994 can be considered as a novel therapeutic target against pancreatic cancer.

Inflammatory Bowel Disease and Primary Sclerosing Cholangitis: A Review of the Phenotype and Associated Specific Features

Primary sclerosing cholangitis (PSC) is a chronic, progressive cholestatic disease that is associated with inflammatory bowel disease (IBD) in approximately 70% of cases. Although the pathogenesis is still unknown for both diseases, there is increasing evidence to indicate that they share a common underlying predisposition. Herein, we review the epidemiology, diagnosis, disease pathogenesis, and specific clinical features of the PSC-IBD phenotype. Patients with PSC-IBD have a distinct IBD phenotype with an increased incidence of pancolitis, backwash ileitis, and rectal sparing. Despite often having extensive colonic involvement, these patients present with mild intestinal symptoms or are even asymptomatic, which can delay the diagnosis of IBD. Although the IBD phenotype has been well characterized in PSC patients, the natural history and disease behavior of PSC in PSC-IBD patients is less well defined. There is conflicting evidence regarding the course of IBD in PSC-IBD patients who receive liver transplantation and their risk of recurrent PSC. IBD may also be associated with an increased risk of cholangiocarcinoma in PSC patients. Overall, the PSC-IBD population has an increased risk of developing colorectal neoplasia compared to the conventional IBD population. Lifelong annual surveillance colonoscopy is currently recommended.

PFOA and ulcerative colitis

INTRODUCTION

PFOA (perfluoroctanoic acid) is a perfluoroalkyl substance (PFAS). Although use in the US has been phased out, PFOA persists indefinitely in the environment, and is present in the serum of virtually all people in industrialized countries. Approximately 6 million Americans drink water comtaminated with PFOA above EPA-recommended levels. In a previous cohort study (n = 32,000), we found a strong positive exposure-response relation between PFOA serum levels and subsequent ulcerative colitis (UC) in a high-exposed population from the mid-Ohio valley, but no association with Crohn's disease. In the present study we aimed to determine if UC cases had higher levels of PFOA than did controls or Crohn's disease patients.

METHODS

We measured PFOA and three other PFAS in the serum of 114 UC patients, 60 Crohn's disease patients, and 75 controls, within a year of diagnosis. We conducted regression analyses to assess the association of the PFAS with diagnosis.

RESULTS

The mean age of subjects was 17 years. The mean year of diagnosis was 2007. Mean levels of PFAS were similar to US levels. Mean log PFOA level in UC patients was 38% higher (p = 0.01) than the combined group of Crohn's disease and controls. In contrast, the three other PFASs were significantly higher in controls and Crohn's patients than UC patients. The odds ratio for UC per one unit of log PFOA was 1.60 (95% CI 1.14-2.24), but the trend by quintiles was not monotonic (1, 0.84, 40.98, 33.36, 2.86).

CONCLUSION

We found higher serum PFOA in UC cases compared to Crohn's disease patients or controls, in contrast to other PFAS. Our research is limited by not knowing if the elevated PFOA preceded UC in this population.

The influence of vitamin D on M1 and M2 macrophages in patients with Crohn's disease

Defective bacterial clearance by macrophages plays an important role in Crohn's disease (CD). Phenotypes and functions of inflammatory M1 and anti-inflammatory M2 have not been studied in CD. Vitamin D supplementation reduces the severity of CD by unclear mechanisms. We studied macrophage characteristics in CD and controls and the effects of 1,25 vitamin D (1,25D). PBMC were isolated from CD patients and controls. M1 and M2 were generated by culturing of monocytes with GM-CSF and M-CSF, respectively. CD M1 and M2 showed normal phagocytosis and chemotaxis to CCL2 and fMLP. LPS-induced production of TNF-α, IL-12p40 and IL-10 was comparable between groups. Phagocytosis was unaltered with 1,25D; migration only increased marginally. M1 produced more IL-12p40 and TNF-α; IL-10 was greater in M2. 1,25D markedly decreased IL-12p40 by M1 and M2. 1,25D decreased TNF-α in CD M1; IL-10 levels were unaffected. M2 express F13A1, PTGS2, CD163, CXCL10, CD14 and MMP2, whereas TGF-β, CCL1 and CYP27B1 expression was higher in M1. Marker expression was similar between CD and controls. M1 and M2 markers were not differentially modulated by 1,25D. CD macrophages are not functionally or phenotypically different vs.

CONTROLS

1,25D markedly decreased pro-inflammatory M1 cytokines but did not modulate polarization to anti-inflammatory M2 phenotype.

Effects of Melatonin on Intestinal Microbiota and Oxidative Stress in Colitis Mice

This study investigated the antioxidant capacity and intestinal bacteria community in a mouse model of DSS-induced colitis. Twenty mice were randomly assigned to two treatments: mice with colitis induced by 5% DSS (DSS group) and mice with colitis induced by 5% DSS that also received melatonin treatment (MEL group). The DSS group showed significantly less antioxidant capability than the MEL group, but the two groups did not differ significantly in terms of diversity index (Shannon and Simpson), bacterial culture abundance (Chao1 and ACE), and coverage (Good's coverage estimator). Bacteroidetes were the most abundant phylum in the DSS group (58.93%), followed by Firmicutes with 31.46% and Proteobacteria with 7.97%. In contrast, Firmicutes were the most abundant in the MEL group (49.48%), followed by Bacteroidetes with 41.63% and Proteobacteria with 7.50%. The results support the use of melatonin for prevention of intestinal bowel disease due to its modulatory effect on antioxidant capability and microbiota in mice with colitis. Melatonin was demonstrated to improve the oxidative stress resistance of mice with colitis and regulate the intestinal microbial flora, thus improving intestinal health.

A decade of research on the 17q12-21 asthma locus: Piecing together the puzzle

Chromosome 17q12–21 remains the most highly replicated and significant asthma locus. Genotypes in the core region defined by the first genome-wide association study correlate with expression of 2 genes, ORM1-like 3 (ORMDL3) and gasdermin B (GSDMB), making these prime candidate asthma genes, although recent studies have implicated gasdermin A (GSDMA) distal to and post-GPI attachment to proteins 3 (PGAP3) proximal to the core region as independent loci. We review 10 years of studies on the 17q12–21 locus and suggest that genotype-specific risks for asthma at the proximal and distal loci are not specific to early-onset asthma and mediated by PGAP3, ORMDL3, and/or GSDMA expression. We propose that the weak and inconsistent associations of 17q single nucleotide polymorphisms with asthma in African Americans is due to the high frequency of some 17q alleles, the breakdown of linkage disequilibrium on African-derived chromosomes, and possibly different early-life asthma endotypes in these children. Finally, the inconsistent association between asthma and gene expression levels in blood or lung cells from older children and adults suggests that genotype effects may mediate asthma risk or protection during critical developmental windows and/or in response to relevant exposures in early life. Thus studies of young children and ethnically diverse populations are required to fully understand the relationship between genotype and asthma phenotype and the gene regulatory architecture at this locus. (J Allergy Clin Immunol 2018;142:749–64.)

Crohn's disease

Crohn's disease is a chronic inflammatory bowel disease of unknown etiology associated with an impaired immune response, with periods of activity and remission. It is characterised by patchy and transmural lesions which can affect the entire gastrointestinal tract, from the mouth to the anus. The most frequent symptoms are abdominal pain and diarrhoea, which can seriously affect patients' quality of life. The increasing incidence and prevalence of the disease in our area has had a large impact on clinical practice, with the rapid development of diagnostic and therapeutic techniques. To reduce the risk of complications, primary care physicians and gastroenterologists should be familiar with the management of the disease.

Investigation of inflammatory bowel disease risk factors in 4 families in central China

The prevalence of inflammatory bowel disease (IBD), including Crohn's disease (CD) and ulcerative colitis (UC), is increasing markedly in China. The present study performed pedigree analysis of 4 families with a history of IBD and investigated the association of genetic and environmental factors with susceptibility to IBD. A total of 10 IBD patients (8 CD patients and 2 UC patients) and 90 family members were included in the present study. The clinical characteristics of familial subjects were compared with those of patients with sporadic IBD. Previously reported mutations, namely interleukin-10 receptor (IL10R)-A Thr84Ile, IL10RA Gly141Arg, IL10RB Trp159X, X-linked inhibitor of apoptosis (XIAP) Cys203Tyr, nucleotide-binding oligomerization domain-containing protein 2 (NOD2) Arg702Trp, NOD2 Gly908Arg and NOD2 Leu1007fsinsC, were screened in the patients with IBD, and selected demographic factors were compared between the patients and their unaffected family members. It was observed that single-gene and multi-gene inheritance patterns contributed to IBD in Chinese families. Based on data from the registry system, the ratio of patients with a family history of IBD was 1.25%, which was lower than that in the Western population. First-degree relatives were found to be more susceptible to IBD, and siblings were affected more frequently. Furthermore, the median age of diagnosis was younger in familial patients than in sporadic patients (29.0 vs. 36.0 for CD; 35.5 vs. 41.0 for UC). However, none of the 7 susceptibility loci were present in any of the familial patients. Immigration was a significant risk factor of IBD (odds ratio: 4.667; 95% confidence interval: 1.165-18.690; P=0.021). In conclusion, genetic heterogeneity exits between Chinese families with IBD and the Western population. The present findings suggest that genetic background and environmental factors serve a role in the pathogenesis of IBD.

Rates of hospitalization among African American and Caucasian American patients with Crohn's disease seen at a tertiary care center

BACKGROUND

There is equivocal evidence regarding differences in the clinical course and outcomes of Crohn's disease (CD) among African Americans compared with Caucasian Americans. We sought to analyze whether African Americans with CD are more likely to be hospitalized for CD-related complications when compared with Caucasian Americans with CD.

METHODS

We conducted a retrospective cohort study including 909 African Americans and Caucasian Americans with CD who were seen at our tertiary care Inflammatory Bowel Disease (IBD) referral center between 2000 and 2013. We calculated the rate of hospitalization for CD-related complications among African Americans and Caucasian Americans separately. Zero-inflated Poisson regression models with robust variance estimates were used to estimate crude and multivariable adjusted rate ratios (RR) for CD-related hospitalizations. Multivariable adjusted models included adjustment for age, sex, duration of CD, smoking and CD therapy.

RESULTS

The cumulative rate of CD-related hospital admissions was higher among African American patients compared with Caucasian American patients (395.6/1000 person-years in African Americans vs. 230.4/1000 person-years in Caucasian Americans). Unadjusted and multivariable adjusted rate ratios for CD-related hospitalization comparing African Americans and Caucasian Americans were 1.59 (95% confidence interval [95%CI]: 1.10-2.29; P=0.01) and 1.44 (95%CI: 1.02-2.03; P=0.04), respectively.

CONCLUSIONS

African Americans with CD followed at a tertiary IBD-referral center had a higher rate for CD-related hospitalizations compared with Caucasian Americans. Future studies should examine whether socioeconomic status and biologic markers of disease status could explain the higher risk observed among African Americans.

Crohn's Disease: Genetics Update

Since the discovery of the first Crohn's disease (CD) gene NOD2 in 2001, 140 genetic loci have been found in whites using high-throughput genome-wide association studies. Several genes influence the CD subphenotypes and treatment response. With the observations of increasing prevalence in Asia and developing countries and the incomplete explanation of CD variance, other underexplored areas need to be integrated through novel methodologies. Algorithms that incorporate specific genetic risk alleles with other biomarkers will be developed and used to predict CD disease course, complications, and response to specific therapies, allowing precision medicine to become real in CD.

Chromosome 17q21 Genes ORMDL3 and GSDMB in Asthma and Immune Diseases

Chromosome 17q21 contains a cluster of genes including ORMDL3 and GSDMB, which have been highly linked to asthma in genome-wide association studies. ORMDL3 is localized to the endoplasmic reticulum and regulates downstream pathways including sphingolipids, metalloproteases, remodeling genes, and chemokines. ORMDL3 inhibits serine palmitoyl-CoA transferase, the rate-limiting enzyme for sphingolipid biosynthesis. In addition, ORMDL3 activates the ATF6α branch of the unfolded protein response which regulates SERCA2b and IL-6, pathways of potential importance to asthma. The SNP-linking chromosome 17q21 to asthma is associated with increased ORMDL3 and GSDMB expression. Mice expressing either increased levels of human ORMDL3, or human GSDMB, have an asthma phenotype characterized by increased airway responsiveness and increased airway remodeling (increased smooth muscle and fibrosis) in the absence of airway inflammation. GSDMB regulates expression of 5-LO and TGF-β1 which are known pathways involved in the pathogenesis of asthma. GSDMB is one of four members of the GSDM family (GSDMA, GSDMB, GSDMC, and GSDMD). GSDMD (located on chromosome 8q24 and not linked to asthma) has emerged as a key mediator of pyroptosis. GSDMD is a key component of the NLPR3 inflammasome and is required for its activation. GSDMD undergoes proteolytic cleavage by caspase-1 to release its N-terminal fragment, which in turn mediates pyroptosis and IL-1β secretion. Chromosome 17q21 has not only been linked to asthma but also to type 1 diabetes, inflammatory bowel disease, and primary biliary cirrhosis suggesting that future insights into the biology of genes located in this region will increase our understanding of these diseases.

Re: Genome-Wide Association Study Identifies African-Specific Susceptibility Loci in African Americans With Inflammatory Bowel Disease

BACKGROUND & AIMS

The inflammatory bowel diseases (IBD) ulcerative colitis (UC) and Crohn’s disease (CD) cause significant morbidity and are increasing in prevalence among all populations, including African Americans. More than 200 susceptibility loci have been identified in populations of predominantly European ancestry, but few loci have been associated with IBD in other ethnicities.

METHODS

We performed 2 high-density, genome-wide scans comprising 2345 cases of African Americans with IBD (1646 with CD, 583 with UC, and 116 inflammatory bowel disease unclassified) and 5002 individuals without IBD (controls, identified from the Health Retirement Study and Kaiser Permanente database). Single-nucleotide polymorphisms (SNPs) associated at P < 5.0 × 10⁻⁸ in meta-analysis with a nominal evidence (P < .05) in each scan were considered to have genome-wide significance.

RESULTS

We detected SNPs at HLA-DRB1, and African-specific SNPs at ZNF649 and LSAMP, with associations of genome-wide significance for UC. We detected SNPs at USP25 with associations of genome-wide significance for IBD. No associations of genome-wide significance were detected for CD. In addition, 9 genes previously associated with IBD contained SNPs with significant evidence for replication (P < 1.6 × 10⁻⁶): ADCY3, CXCR6, HLA-DRB1 to HLA-DQA1 (genome-wide signifi-cance on conditioning), IL12B, PTGER4, and TNC for IBD; IL23R, PTGER4, and SNX20 (in strong linkage disequilibrium with NOD2) for CD; and KCNQ2 (near TNFRSF6B) for UC. Several of these genes, such as TNC (near TNFSF15), CXCR6, and genes associated with IBD at the HLA locus, contained SNPs with unique association patterns with African-specific alleles.

CONCLUSIONS

We performed a genome-wide association study of African Americans with IBD and identified loci associated with UC in only this population; we also replicated IBD, CD, and UC loci identified in European populations. The detection of variants associated with IBD risk in only people of African descent demonstrates the importance of studying the genetics of IBD and other complex diseases in populations beyond those of European ancestry.

Crohn's disease

Crohn's disease is a chronic inflammatory disease of the gastrointestinal tract, with increasing incidence worldwide. Crohn's disease might result from a complex interplay between genetic susceptibility, environmental factors, and altered gut microbiota, leading to dysregulated innate and adaptive immune responses. The typical clinical scenario is a young patient presenting with abdominal pain, chronic diarrhoea, weight loss, and fatigue. Assessment of disease extent and of prognostic factors for complications is paramount to guide therapeutic decisions. Current strategies aim for deep and long-lasting remission, with the goal of preventing complications, such as surgery, and blocking disease progression. Central to these strategies is the introduction of early immunosuppression or combination therapy with biologicals in high-risk patients, combined with a tight and frequent control of inflammation, and adjustment of therapy on the basis of that assessment (treat to target strategy). The therapeutic armamentarium for Crohn's disease is expanding, and therefore the need to develop biomarkers that can predict response to therapies will become increasingly important for personalised medicine decisions in the near future. In this Seminar, we provide a physician-oriented overview of Crohn's disease in adults, ranging from epidemiology and cause to clinical diagnosis, natural history, patient stratification and clinical management, and ending with an overview of emerging therapies and future directions for research.

Genetic Characterization and Influence on Inflammatory Bowel Disease Expression in a Diverse Hispanic South Florida Cohort

OBJECTIVES

Hispanics represent an understudied inflammatory bowel disease (IBD) population. Prior studies examining genetic predisposition to IBD in Hispanics are limited. In this study, we examined whether European-derived IBD variants confer risk in Hispanics and their influence on IBD phenotype in Hispanics compared to non-Hispanic whites (NHW).

METHODS

Self-identified Hispanics and NHWs with IBD were included. Hispanic controls were included for our genetic analyses. We performed single-variant testing at previously identified Crohn's disease (CD) and ulcerative colitis (UC) IBD variants in Hispanic cases and controls. These risk variants were used to compute individual genetic risk scores. Genetic risk scores and phenotype associations were compared between Hispanic and NHW.

RESULTS

A total of 1,115 participants were included: 698 controls and 417 IBD patients (230 Hispanics). We found evidence of association within our Hispanic cohort at 22 IBD risk loci, with ~76% of the risk loci demonstrating over-representation of the European risk allele; these included loci corresponding to IL23R and NOD2 genes. CD genetic risk score for Hispanics (199.67) was similar to the score for NHW (200.33), P=0.51; the same was true in UC. Genetic risk scores did not predict IBD phenotype or complications in Hispanics or NHW except for a younger age of CD onset in Hispanics (P=0.04).

CONCLUSIONS

This study highlights the fundamental importance of these loci in IBD pathogenesis including in our diverse Hispanic population. Future studies looking at non-genetic mechanisms of disease are needed to explain differences in age of presentation and phenotype between Hispanics and NHW.

Understanding and Preventing the Global Increase of Inflammatory Bowel Disease

The inflammatory bowel diseases (IBDs) are contemporary conditions of industrialized societies. The prevalence of IBD continues to increase steadily in Western countries, and newly industrialized countries have a rapidly increasing incidence. The global spread of IBD appears to associate with Westernization of diets and environments, which affects the intestinal microbiome and increases the risk of IBD in genetically susceptible individuals. It is important to increase our understanding of these events to slow progression of IBD. We present a long-term plan to develop interventions that slow or stop the global increase in the incidence of IBD.

Genome-Wide Association Study Identifies African-Specific Susceptibility Loci in African Americans With Inflammatory Bowel Disease

BACKGROUND & AIMS

The inflammatory bowel diseases (IBD) ulcerative colitis (UC) and Crohn's disease (CD) cause significant morbidity and are increasing in prevalence among all populations, including African Americans. More than 200 susceptibility loci have been identified in populations of predominantly European ancestry, but few loci have been associated with IBD in other ethnicities.

METHODS

We performed 2 high-density, genome-wide scans comprising 2345 cases of African Americans with IBD (1646 with CD, 583 with UC, and 116 inflammatory bowel disease unclassified) and 5002 individuals without IBD (controls, identified from the Health Retirement Study and Kaiser Permanente database). Single-nucleotide polymorphisms (SNPs) associated at P < 5.0 × 10-8 in meta-analysis with a nominal evidence (P < .05) in each scan were considered to have genome-wide significance.

RESULTS

We detected SNPs at HLA-DRB1, and African-specific SNPs at ZNF649 and LSAMP, with associations of genome-wide significance for UC. We detected SNPs at USP25 with associations of genome-wide significance for IBD. No associations of genome-wide significance were detected for CD. In addition, 9 genes previously associated with IBD contained SNPs with significant evidence for replication (P < 1.6 × 10-6): ADCY3, CXCR6, HLA-DRB1 to HLA-DQA1 (genome-wide significance on conditioning), IL12B,PTGER4, and TNC for IBD; IL23R, PTGER4, and SNX20 (in strong linkage disequilibrium with NOD2) for CD; and KCNQ2 (near TNFRSF6B) for UC. Several of these genes, such as TNC (near TNFSF15), CXCR6, and genes associated with IBD at the HLA locus, contained SNPs with unique association patterns with African-specific alleles.

CONCLUSIONS

We performed a genome-wide association study of African Americans with IBD and identified loci associated with UC in only this population; we also replicated IBD, CD, and UC loci identified in European populations. The detection of variants associated with IBD risk in only people of African descent demonstrates the importance of studying the genetics of IBD and other complex diseases in populations beyond those of European ancestry.

Pouchitis after ileal pouch-anal anastomosis in ulcerative colitis: Diagnosis, management, risk factors, and incidence

Restorative proctocolectomy with ileal pouch-anal anastomosis has been the surgical treatment of choice for patients with ulcerative colitis who require surgery. Quality of life after this procedure is satisfactory in most cases; however, pouchitis is a troublesome condition involving inflammation of the ileal pouch. When a patient presents with symptoms of pouchitis, such as increased bowel movements, mucous and/or bloody exudates, abdominal cramps, and fever, endoscopy is essential for a precise diagnosis. The proximal ileum and rectal cuff, as well as the ileal pouch, should be endoscopically observed. The reported incidence of pouchitis ranges from 14% to 59%, and antibiotic therapy is the primary treatment for acute pouchitis. Chronic pouchitis includes antibiotic-dependent and refractory pouchitis. Intensive therapy including antitumor necrosis factor antibodies and steroids may be necessary for antibiotic-refractory pouchitis, and pouch failure may occur despite such intensive treatment. Reported risk factors for the development of pouchitis include presence of extraintestinal manifestations, primary sclerosing cholangitis, non-smoking, and postoperative non-steroidal anti-inflammatory drug usage. In the present review, we focus on the diagnosis, endoscopic features, management, incidence, and risk factors of pouchitis in patients with ulcerative colitis who underwent ileal pouch-anal anastomosis.

Doxycycline, metronidazole and isotretinoin: Do they modify microRNA/mRNA expression profiles and function in murine T-cells?

Inflammatory bowel disease (IBD) may develop due to an inflammatory response to commensal gut microbiota triggered by environmental factors in a genetically susceptible host. Isotretinoin (acne therapy) has been inconsistently associated with IBD onset and flares but prior treatment with antibiotics, also associated with IBD development, complicates the confirmation of this association. Here we studied in mice whether doxycycline, metronidazole or isotretinoin induce epigenetic modifications, and consequently change T-cell mRNA expression and/or function directly after treatment and after a 4 week recovery period. Isotretinoin induced IL-10 signaling in Tregs and naive T-cells directly after treatment and reduced effector T-cell proliferation alone and in co-culture with Tregs. Metronidazole activated processes associated with anti-inflammatory pathways in both T-cell subsets directly after the treatment period whereas doxycycline induced an immediate pro-inflammatory expression profile that resolved after the recovery period. Long-term changes indicated an inhibition of proliferation by doxycycline and induction of beneficial immune and metabolic pathways by metronidazole. Persistent alterations in microRNA and mRNA expression profiles after the recovery period indicate that all three medications may induce long-term epigenetic modifications in both T-cell subsets. Yet, our data do not support the induction of a long-term pro-inflammatory phenotype in murine Tregs and naive T-cells.

Crohn's Disease: Evolution, Epigenetics, and the Emerging Role of Microbiome-Targeted Therapies

Crohn's disease (CD) is a chronic, systemic, immune-mediated inflammation of the gastrointestinal tract. Originally described in 1932 as non-caseating granulomatous inflammation limited to the terminal ileum, it is now recognized as an expanding group of heterogeneous diseases defined by intestinal location, extent, behavior, and systemic extraintestinal manifestations. Joint diseases, including inflammatory spondyloarthritis and ankylosing spondylitis, are the most common extraintestinal manifestations of CD and share more genetic susceptibility loci than any other inflammatory bowel disease (IBD) trait. The high frequency and overlap with genes associated with infectious diseases, specifically Mendelian susceptibility to mycobacterial diseases (MSMD), suggest that CD may represent an evolutionary adaptation to environmental microbes. Elucidating the diversity of the enteric microbiota and the protean mucosal immune responses in individuals may personalize microbiome-targeted therapies and molecular classifications of CD. This review will focus on CD's natural history and therapies in the context of epigenetics, immunogenetics, and the microbiome.

Why Are Omics Technologies Important to Understanding the Role of Nutrition in Inflammatory Bowel Diseases?

For many years, there has been confusion about the role that nutrition plays in inflammatory bowel diseases (IBD). It is apparent that good dietary advice for one individual may prove inappropriate for another. As with many diseases, genome-wide association studies across large collaborative groups have been important in revealing the role of genetics in IBD, with more than 200 genes associated with susceptibility to the disease. These associations provide clues to explain the differences in nutrient requirements among individuals. In addition to genes directly involved in the control of inflammation, a number of the associated genes play roles in modulating the gut microbiota. Cell line models enable the generation of hypotheses as to how various bioactive dietary components might be especially beneficial for certain genetic groups. Animal models are necessary to mimic aspects of the complex aetiology of IBD, and provide an important link between tissue culture studies and human trials. Once we are sufficiently confident of our hypotheses, we can then take modified diets to an IBD population that is stratified according to genotype. Studies in IBD patients fed a Mediterranean-style diet have been important in validating our hypotheses and as a proof-of-principle for the application of these sensitive omics technologies to aiding in the control of IBD symptoms.

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

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