Monozygotic twins with Crohn's disease and ulcerative colitis: a unique case report

The Gut Microbiome and the Triple Environmental Hit Concept of Inflammatory Bowel Disease Pathogenesis

The incidence of chronic inflammatory bowel diseases (IBDs), such as Crohn's disease (CD) and ulcerative colitis (UC) have significantly increased in recent decades implicating environmental effects. The developmental origin of disease concept provides a theoretical framework by which the complex interplay between environmental factors and host cells, particularly during vulnerable time periods, ultimately cause disease, such as IBD. Epigenetics has been proposed as the underlying mechanism within this concept, turning environmental triggers into stable changes of cellular function. Adding further to the complexity of IBD is the gut microbiome, which is equally responsive to the environment, and can impact host cell function, where recent findings underscore the stochastic and individualized nature of such effects. We review the microbiome literature through a novel triple environmental hit concept (priming, modulation, and trigger) of IBD pathogenesis. We propose that there are at least 3 distinct stages during an individual's lifespan where random/stochastic events driven by environmental influences are necessary for ultimately developing IBD. By this means, we speculate that microbiome-directed therapeutics carry potential for individualized prevention and dynamic treatment of IBD.

Impact of Paneth Cell Autophagy on Inflammatory Bowel Disease

Intestinal mucosal barrier, mainly consisting of the mucus layer and epithelium, functions in absorbing nutrition as well as prevention of the invasion of pathogenic microorganisms. Paneth cell, an important component of mucosal barrier, plays a vital role in maintaining the intestinal homeostasis by producing antimicrobial materials and controlling the host-commensal balance. Current evidence shows that the dysfunction of intestinal mucosal barrier, especially Paneth cell, participates in the onset and progression of inflammatory bowel disease (IBD). Autophagy, a cellular stress response, involves various physiological processes, such as secretion of proteins, production of antimicrobial peptides, and degradation of aberrant organelles or proteins. In the recent years, the roles of autophagy in the pathogenesis of IBD have been increasingly studied. Here in this review, we mainly focus on describing the roles of Paneth cell autophagy in IBD as well as several popular autophagy-related genetic variants in Penath cell and the related therapeutic strategies against IBD.

Challenges for epigenetic research in inflammatory bowel diseases

The human epigenome may link environmental exposures and commensal microbiota changes to host pathology in respect to the developmental origins of inflammatory bowel diseases (ulcerative colitis [UC] and Crohn's disease [more appropriately Crohn disease, CD]). Genetic predisposition - prenatal, perinatal and pediatric environmental influences - microbiome aberration (dysbiosis) and immune dysregulation appear to be important elements in disease development, progression and maintenance. The prevalence of combined genetic and epigenetic susceptibility toward UC and CD is calculated herein to be as high as 2%, and approximately 1% for UC and CD in highly developed countries, respectively. This review emphasizes the significant challenges for epigenetic research in inflammatory bowel diseases. Overcoming these challenges, however, could reveal unique opportunities for disease prevention, treatment and possible cure.

Paternal chronic colitis causes epigenetic inheritance of susceptibility to colitis

Inflammatory bowel disease (IBD) arises by unknown environmental triggers in genetically susceptible individuals. Epigenetic regulation of gene expression may integrate internal and external influences and may thereby modulate disease susceptibility. Epigenetic modification may also affect the germ-line and in certain contexts can be inherited to offspring. This study investigates epigenetic alterations consequent to experimental murine colitis induced by dextran sodium sulphate (DSS), and their paternal transmission to offspring. Genome-wide methylome- and transcriptome-profiling of intestinal epithelial cells (IECs) and sperm cells of males of the F₀ generation, which received either DSS and consequently developed colitis (F₀^DSS), or non-supplemented tap water (F₀^Ctrl) and hence remained healthy, and of their F₁ offspring was performed using reduced representation bisulfite sequencing (RRBS) and RNA-sequencing (RNA-Seq), respectively. Offspring of F₀^DSS males exhibited aberrant methylation and expression patterns of multiple genes, including Igf1r and Nr4a2, which are involved in energy metabolism. Importantly, DSS colitis in F₀^DSS mice was associated with decreased body weight at baseline of their F₁ offspring, and these F₁ mice exhibited increased susceptibility to DSS-induced colitis compared to offspring from F₀^Ctrl males. This study hence demonstrates epigenetic transmissibility of metabolic and inflammatory traits resulting from experimental colitis.

The association between three promoter polymorphisms of IL-10 and inflammatory bowel diseases (IBD): a meta-analysis

AIM

To assess the relationship of the Interleukin-10 (IL-10) -1082G/A (rs1800896), -819C/T (rs1800871) and -592C/A (rs1800872) polymorphism with inflammatory bowel disease (IBD) by means of meta-analysis.

METHODS

Published data addressing the association between polymorphism of the IL-10 with Crohn's disease (CD) and Ulcerative colitis (UC) were selected from electronic databases. A total of 17 studies including 4132 cases and 5109 controls were included in this meta-analysis which detected whether -1082G/A, -819C/T and -592C/A polymorphism were associated with CD or UC susceptibility.

RESULT

The IL-10 -819C/T and -519C/A variant allele observed a significant association with UC (OR 1.16, 95%CI 1.03-1.31 and OR 1.19, 95%CI 1.03-1.38) not CD while there is no significant association between -1082G/A and UC or CD.

CONCLUSION

The IL-10 -819C/T and -592C/A polymorphisms contribute to susceptibility to UC, but IL-10 -1082G/A polymorphism neither associated with CD nor UC.

Crohn disease: a current perspective on genetics, autophagy and immunity

Crohn disease (CD) is a chronic and debilitating inflammatory condition of the gastrointestinal tract. Prevalence in Western populations is 100-150/100,000 and somewhat higher in Ashkenazi Jews. Peak incidence is in early adult life, although any age can be affected and a majority of affected individuals progress to relapsing and chronic disease. Medical treatments rely significantly on empirical corticosteroid therapy and immunosuppression, and intestinal resectional surgery is frequently required. Thus, 80% of patients with CD come to surgery for refractory disease or complications. It is hoped that an improved understanding of pathogenic mechanisms, for example by studying the genetic basis of CD and other forms of inflammatory bowel diseases (IBD), will lead to improved therapies and possibly preventative strategies in individuals identified as being at risk.

Crohn disease: a current perspective on genetics, autophagy and immunity

Crohn disease (CD) is a chronic and debilitating inflammatory condition of the gastrointestinal tract. Prevalence in Western populations is 100-150/100,000 and somewhat higher in Ashkenazi Jews. Peak incidence is in early adult life, although any age can be affected and a majority of affected individuals progress to relapsing and chronic disease. Medical treatments rely significantly on empirical corticosteroid therapy and immunosuppression, and intestinal resectional surgery is frequently required. Thus, 80% of patients with CD come to surgery for refractory disease or complications. It is hoped that an improved understanding of pathogenic mechanisms, for example by studying the genetic basis of CD and other forms of inflammatory bowel diseases (IBD), will lead to improved therapies and possibly preventative strategies in individuals identified as being at risk.

Association of ATG16L1 and IRGM genes polymorphisms with inflammatory bowel disease: a meta-analysis approach

The aim of this study was to determine the role of the ATG16L1 (rs2241880) and IRGM (rs13361189 and rs4958847) genes polymorphism in Crohn's disease (CD) and ulcerative colitis (UC). Our study included 557 CD and 425 UC patients and 672 ethnically matched Spanish controls and a meta-analysis with the data published to date. The polymorphisms were genotyped using predesigned TaqMan single nucleotide polymorphism genotyping assays. There was a statistically significant difference in the distribution of the ATG16L1 rs2241880 G allele between CD patients and controls in the Spanish population: P=6.5 x 10(-9), odds ratio (OR)=1.62. Although no differences were observed between UC patients and controls in the Spanish cohort, a meta-analysis demonstrated that the ATG16L1 G allele increase significantly risk for UC (P=0.0003, pooled OR=1.08). In addition, our meta-analysis data showed that IRGM rs13361189 and rs4958847 polymorphisms were associated with CD (rs13361189 C allele P=1.07 x 10(-19), pooled OR=1.34; rs4958847 A allele P=2.78 x 10(-17), pooled OR=1.31) and UC (rs13361189 P=0.0069, pooled OR=1.16; rs4958847 P=0.014, pooled OR=1.13). In conclusion, our results confirm the ATG16L1 rs2241880 and IRGM rs13361189 and rs4958847 polymorphisms as important markers for CD susceptibility and indicate that these variants are also associated with UC.

Classification of genetic profiles of Crohn's disease: a focus on the ATG16L1 gene

Inflammatory bowel disease constitutes two related clinical entities, Crohn's disease (CD) and ulcerative colitis (UC), both of which have increased in prevalence over the last decade. Family and twin studies have strongly indicated that genetic factors play a large role in an individual's risk of developing inflammatory bowel disease. Despite this, it has proven difficult to isolate disease genes that confer susceptibility to this disease using classical candidate gene and linkage approaches, with the notable exception of the isolation of the caspase recruitment domain family, member 15 (CARD15) gene. However, over the last 2 years, genome-wide association (GWA) studies have become feasible, where modern high-throughput single nucleotide polymorphism (SNP) genotyping technologies can be applied to large and comprehensively phenotyped patient cohorts. Such approaches have enabled scientists to robustly associate specific variants with many complex diseases, including age-related macular degeneration, Type 2 diabetes, breast cancer and asthma. In the inflammatory bowel disease field, positive associations with CD and UC coming from GWA studies have been reported for an ever increasing number of genes. The most consistently and strongly associated variants have been in the CARD15, the interleukin 23 receptor (IL23R) and autophagy-related 16-like 1 (ATG16L1) genes. With respect to ATG16L1, the G allele of SNP rs2241880 has been shown in multiple association studies to confer strong risk for CD, although its association with UC remains more debatable. This SNP is in fact a common coding variant, specifically a threonine-to-alanine substitution at amino acid position 300 of the ATG16L1 protein (T300A), and appears to account for all of the disease risk conferred by this locus. This review addresses recent advances in GWA studies of inflammatory bowel disease, with specific focus on the growing evidence of the ATG16L1 gene's role in CD and how its protein product operating within the autophagic pathway makes autophagy an attractive therapeutic target for this debilitating disorder.

Pediatric inflammatory bowel disease: clinical and molecular genetics

Pediatric-onset inflammatory bowel disease (IBD) is characterized by distinct phenotypic differences compared to adult-onset IBD. This raises the question whether early (pediatric) onset IBD represents the same disease process occurring in adults but merely at an earlier age or does IBD in children have a very different etiology and pathogenesis but with the same clinical presentation as adults. The use of techniques such as whole genome association studies to perform broad, unbiased screening for the contributions of common genetic variations to complex disease has rapidly assisted in the identification of several novel susceptibility loci associated with pediatric-onset Crohn's disease such as IL23R and ATG16L1. These genes join the already confirmed IBD susceptibility genes such as NOD2/CARD15, IBD5, and DLG5. Therefore, there is hope that advances in the field of clinical and molecular genetics will assist in answering the fundamental question of whether pediatric IBD has a different etiology and pathogenesis compared to adult IBD. This review examines the current status of clinical and molecular genetics of pediatric IBD, and highlights the differences between pediatric and adult IBD in disease phenotypes and genotypes. Finally, the future directions of genetic investigations in pediatric IBD are discussed.

Update on the genetics of inflammatory bowel disease

There is a general consensus that interplay of genetic and environmental factors leads to an overactive mucosal immune response, which mediates the tissue damage in inflammatory bowel disease. Ethnic aggregation of inflammatory bowel disease (particularly, increased incidence and prevalence in the Ashkenazim), familial aggregation of inflammatory bowel disease, and greater concordance for inflammatory bowel disease in monozygotic twins than dizygotic twins are 3 lines of evidence for a central role of genetic factors in the pathogenesis. The genetics of inflammatory bowel disease cannot be explained by simple Mendelian genetics; it is characterized by incomplete penetrance, multiple susceptibility loci and genetic heterogeneity. Unraveling the complex genetics of inflammatory bowel disease is a daunting challenge, but the perseverance of inflammatory bowel disease gene hunters has produced commendable results in recent years. Since 1996, the field of inflammatory bowel disease genetics has progressed from publication of the first systematic genome searches for inflammatory bowel disease susceptibility loci to the identification of Crohn disease-associated genetic variants in CARD15/NOD2. Strategies for finding additional inflammatory bowel disease genes include taking advantage of the greater resolution and power of linkage disequilibrium mapping, mapping by admixture disequilibrium in African-American and Hispanic-American populations, stratifying genetic analyses by genotypes at known inflammatory bowel disease loci, and refining inflammatory bowel disease phenotypes to reduce genetic heterogeneity and simplify the search for additional inflammatory bowel disease genes.

What are the major arguments in favour of the genetic susceptibility for inflammatory bowel disease?

Epidemiological data, notably concordance rates in twin pairs and familial aggregation, have provided strong evidence for the importance of the genetic contribution in inflammatory bowel diseases. Genome wide scanning has been remarkably successful in identifying a number of susceptibility loci. The identification of the IBD1 gene on chromosome 16 as NOD2/CARD15 definitely establishes that a significant proportion of Crohn's disease has an underlying genetic cause. In addition, our knowledge of the clinical impact of other genes in modelling disease phenotypes has increased in parallel. These results have led to great optimism that important clinical applications will result from genetic research in the near future.

Ulcerative colitis

Ulcerative colitis is a chronic inflammatory disease of the rectum and colon. Results from many studies in people and animals of intestinal inflammation suggest that ulcerative colitis results from environmental factors triggering a loss of tolerance for normal intestinal flora in genetically susceptible individuals. Although progress has been made in the overall management of the disease, no innovative treatment has been developed. By contrast with Crohn's disease, there are few clinical data on biological agents. Probiotics seem the most promising of several experimental and traditional agents that have been investigated in controlled clinical trials.

Clinical aspects and pathophysiology of inflammatory bowel disease

The chronic inflammatory bowel diseases (IBD), Crohn's disease and ulcerative colitis, are recognized as important causes of gastrointestinal disease in children and adults. In this review we delineate the clinical manifestations and diagnostic features of IBD. In addition, we summarize important recent advances in our understanding of the immune mediators of intestinal inflammation. This information has led to new therapeutic approaches in IBD. Further, we discuss the considerable data that point to the significance of genetic factors in the development of IBD and the genetic loci which have been implicated through genome-wide searches. The commensal bacterial flora also appears to be a critical element, particularly in regards to Crohn's disease, although the precise role of the bacteria in the disease manifestations remains unclear. Current investigations promise to yield fresh insights in these areas.

Epidemiology and the natural course of inflammatory bowel disease

Ulcerative colitis and Crohn's disease are inflammatory disorders of the gastrointestinal tract that are distributed unevenly within populations and throughout the world. Although the exact causes of inflammatory bowel disease (IBD) remain unknown, study of the epidemiology of IBD has provided insight into pathogenesis. This article examines the geographic, ethnic, and other trends of IBD; risk factors (including genetic and environmental); and the natural history of IBD.

Paramyxovirus infections in childhood and subsequent inflammatory bowel disease

BACKGROUND & AIMS

Measles virus has been implicated in the etiology of both inflammatory bowel diseases (IBDs), Crohn's disease and ulcerative colitis. Subacute sclerosing panencephalitis (SSPE) is caused by atypical measles infection. This study investigated the patterns of infection that are risks for SSPE, early infection and a close temporal relationship between measles and another infection, as potential risks for IBD.

METHODS

The data are from 7019 members of a nationally representative 1970 British Cohort Study. The ages of five childhood infections were recorded before onset of IBD symptoms. Diagnoses of IBD and insulin-dependent diabetes mellitus (IDDM), as a control disease, were identified by age 26 years.

RESULTS

Mumps infection before age 2 years was a risk for ulcerative colitis (odds ratio, 25.12; 95% confidence interval, 6. 35-99.36). Measles and mumps infections in the same year of life were significantly associated with ulcerative colitis and Crohn's disease, with odds ratios of 7.47 (2.42-23.06) and 4.27 (1.24-14.46), but not with IDDM. These relationships are independent of each other as well as sex, social class at birth, household crowding in childhood, and family history of IBD.

CONCLUSIONS

Atypical paramyxovirus infections in childhood may be risk factors for later IBD.