The intermediate filament protein, vimentin, is a regulator of NOD2 activity

OBJECTIVE

Mutations in the nucleotide-binding oligomerisation domain-containing protein 2 (NOD2) gene remain the strongest genetic determinants for Crohn's disease (CD). Having previously identified vimentin as a novel NOD2-interacting protein, the authors aimed to investigate the regulatory effects of vimentin on NOD2 function and the association of variants in Vim with CD susceptibility.

DESIGN

Coimmunoprecipitation, fluorescent microscopy and fractionation were used to confirm the interaction between NOD2 and vimentin. HEK293 cells stably expressing wild-type NOD2 or a NOD2 frameshift variant (L1007fs) and SW480 colonic epithelial cells were used alongside the vimentin inhibitor, withaferin A (WFA), to assess effects on NOD2 function using the nuclear factor-kappaB (NF-κB) reporter gene, green fluorescent protein-LC3-based autophagy, and bacterial gentamicin protection assays. International genome-wide association meta-analysis data were used to test for associations of single-nucleotide polymorphisms in Vim with CD susceptibility.

RESULTS

The leucine-rich repeat domain of NOD2 contained the elements required for vimentin binding; CD-associated polymorphisms disrupted this interaction. NOD2 and vimentin colocalised at the cell plasma membrane, and cytosolic mislocalisation of the L1007fs and R702W variants correlated with an inability to interact with vimentin. Use of WFA demonstrated that vimentin was required for NOD2-dependent NF-κB activation and muramyl dipeptide-induced autophagy induction, and that NOD2 and vimentin regulated the invasion and survival properties of a CD-associated adherent-invasive Escherichia coli strain. Genetic analysis revealed an association signal across the haplotype block containing Vim.

CONCLUSION

Vimentin is an important regulator of NOD2 function and a potential novel therapeutic target in the treatment of CD. In addition, Vim is a candidate susceptibility gene for CD, supporting the functional data.

Hypothesis: Increased consumption of emulsifiers as an explanation for the rising incidence of Crohn's disease

Crohn's disease (CD) incidence has increased over the past fifty years but the explanation is unclear. CD can be brought into remission by liquid enteral feeding, but the mechanism for this response is unknown. We suggest that consumption of emulsifiers in processed foods may promote CD by increasing bacterial translocation. This is supported by evidence that (i) geographical variation in CD correlates with emulsifier consumption as does the increasing incidence of CD in Japan; (ii) although CD incidence also correlates with fat consumption, the response to enteral feeding is not affected by the fat content of the feed and (iii) very small concentrations of the emulsifier polysorbate 80 enhance bacterial translocation across intestinal epithelia. Undigested emulsifiers may increase bacterial translocation, particularly in the small intestine where the mucus layer is discontinuous. The hypothesis should be testable by trials of enteral feeding with/without emulsifiers.

Associations between genetic polymorphisms in IL-33, IL1R1 and risk for inflammatory bowel disease

BACKGROUND

Recent evidence suggests that the IL-33/IL1RL1 axis plays a critical role in several autoimmune and inflammatory disorders; however, its mechanistic role in inflammatory bowel disease (IBD) has not been clearly defined. We investigated the contribution of IL-33 and IL1RL1 polymorphisms to IBD risk, and possible correlations with phenotype in an Italian cohort of adult and pediatric patients.

METHODS

We evaluated the association of six SNPs in IL-33 and IL1RL1 genes, in 805 Crohn's disease (CD), 816 ulcerative colitis (UC), and 752 controls, using Taqman. IL-33 and IL1RL1 mRNA expression was also analyzed.

RESULTS

Significant allele and genotype associations with IL-33 rs3939286 were found in CD (P = 0.004; P = 0.035) and UC patients (P = 0.002; P = 0.038). After stratifying the cohort for age at diagnosis, the differences remained significant only in the IBD adult-onset. Significant associations were also obtained in CD patients with two IL1RL1 polymorphisms (rs13015714 and rs2058660, P<0.015). By combining homo- and heterozygous carriers of the rs13015714 risk allele, differences were still significant for both CD adult- and pediatric-onset. Upon genotype-phenotype evaluation, an increased frequency of extensive colitis in adult UC (P = 0.019) and in steroid-responsive pediatric patients (P = 0.024) carrying the IL-33 rs3939286 risk genotype, was observed. mRNA expression of IL-33 and IL1RL1 in inflamed IBD biopsy samples was significantly increased.

CONCLUSIONS

Common IL-33 and IL1RL1 polymorphisms contribute to the risk of IBD in an Italian cohort of adult and pediatric patients, with some influence on sub-phenotypes.

Extended haplotype association study in Crohn's disease identifies a novel, Ashkenazi Jewish-specific missense mutation in the NF-κB pathway gene, HEATR3

The Ashkenazi Jewish population has a several-fold higher prevalence of Crohn’s disease compared to non-Jewish European ancestry populations and has a unique genetic history. Haplotype association is critical to Crohn’s disease etiology in this population, most notably at NOD2, in which three causal, uncommon, and conditionally independent NOD2 variants reside on a shared background haplotype. We present an analysis of extended haplotypes which showed significantly greater association to Crohn’s disease in the Ashkenazi Jewish population compared to a non-Jewish population (145 haplotypes and no haplotypes with P-value < 10⁻³, respectively). Two haplotype regions, one each on chromosomes 16 and 21, conferred increased disease risk within established Crohn’s disease loci. We performed exome sequencing of 55 Ashkenazi Jewish individuals and follow-up genotyping focused on variants in these two regions. We observed Ashkenazi Jewish-specific nominal association at R755C in TRPM2 on chromosome 21. Within the chromosome 16 region, R642S of HEATR3 and rs9922362 of BRD7 showed genome-wide significance. Expression studies of HEATR3 demonstrated a positive role in NOD2-mediated NF-κB signaling. The BRD7 signal showed conditional dependence with only the downstream rare Crohn’s disease-causal variants in NOD2, but not with the background haplotype; this elaborates NOD2 as a key illustration of synthetic association.

The microbiota and inflammatory bowel disease: insights from animal models

Inflammatory bowel disease (IBD) is thought to result from a dysregulated immune response to intestinal microbial flora in individuals with genetic predisposition(s). Genome-wide association studies (GWAS) in human IBD have identified more than 150 associated loci, some of which are key players in innate immunity and bacterial handling, reflecting the importance of the microbiota in disease pathogenesis. In fact, the presence of a microbial flora is not only crucial to the development of a normal murine immune system but also critical for the development of disease in the majority of animal models of IBD. Although animal models do not perfectly recapitulate human IBD, they have led to the discovery of important concepts in IBD pathogenesis, such as the central role of microbiota in disease development and perpetuation. Many genetically susceptible models do not develop colitis when raised in a germ-free or Helicobacter-free environment. In fact, disease in most models can be attenuated or completely abolished with antibiotic treatment. Moreover, an interplay between intestinal microbiota and mucosal immune activation is suggested by the presence of serum antibodies against the Cbir1 flagellin, an immunodominant antigen that activates TLR5, in certain models of spontaneous colitis as well as in human patients. Furthermore, T cells reactive to Cbir1 are able to induce disease in recipient mice upon adoptive cell transfer, demonstrating the pro-inflammatory properties of certain bacterial products. In fact, it has been shown that transfer of certain intestinal bacteria from a specific genetically altered mouse model with spontaneous colitis can induce disease in wild-type mice upon co-housing or direct feeding. These observations demonstrate the pathogenic potential of intestinal microbiota in IBD. However, intestinal bacteria are not always maladaptive in mucosal homeostasis. Both Bacteroides fragilis and Clostridium species promote the number and function of a certain regulatory T cell subset in the colon leading to protection against murine colitis. In fact, normal development of regulatory cells and epithelial cell integrity are abolished in the absence of an intestinal flora, suggestive of the need for certain microbial components to induce beneficial anti-inflammatory mechanisms. All in all, altered immune responses to microbes play a crucial role in IBD pathogenesis. However, certain components of the microbiota are also likely critical for normal development of regulatory mechanisms that contribute to mucosal homeostasis. Findings in animal models highlight the concept that IBD is a disease that results from the interplay of genetics and microbial/environmental factors.

The unfolded protein response and gastrointestinal disease

As the inner lining of the gastrointestinal tract, the intestinal epithelium serves an essential role in innate immune function at the interface between the host and microbiota. Given the unique environmental challenges and thus physiologic secretory functions of this surface, it is exquisitely sensitive to perturbations that affect its capacity to resolve endoplasmic reticulum (ER) stress. Genetic deletion of factors involved in the unfolded protein response (UPR), which functions in the resolution of ER stress that arises from misfolded proteins, result in spontaneous intestinal inflammation closely mimicking human inflammatory bowel disease (IBD). This is demonstrated by observations wherein deletion of genes such as Xbp1 and Agr2 profoundly affects the intestinal epithelium and results in spontaneous intestinal inflammation. Moreover, both genes, along with others (e.g., ORDML3) represent genetic risk factors for human IBD, both Crohn's disease and ulcerative colitis. Here, we review the current mechanistic understanding for how unresolved ER stress can lead to intestinal inflammation and highlight the findings that implicate ER stress as a genetically affected biological pathway in IBD. We further discuss environmental and microbial factors that might impact on the epithelium's capacity to resolve ER stress and which may constitute exogenous factors that may precipitate disease in genetically susceptible individuals.

A genome-wide association study identifies 2 susceptibility Loci for Crohn's disease in a Japanese population

BACKGROUND & AIMS

Crohn's disease is an inflammatory bowel disease induced by multiple genetic and environmental factors. Genome-wide association studies have identified genetic factors that affect the risk for Crohn's disease in European populations, but information from other ethnic groups is scarce. We therefore investigated genetic factors associated with Crohn's disease in the Japanese population.

METHODS

We performed a genome-wide association study with 372 individuals with Crohn's disease (cases) and 3389 controls, all from the Japanese population. To confirm identified associations, we performed a replication study with an independent panel of 1151 Crohn's disease cases and 15,800 controls. We also performed an association analysis using genome-wide genotype imputation in the discovery cohort.

RESULTS

We confirmed associations of Crohn's disease with variants in MHC (rs7765379, P = 2.11 × 10(-59)), TNFSF15 (rs6478106, P = 3.87 × 10(-45)), and STAT3 (rs9891119, P = 2.24 × 10(-14)). We identified 2 new susceptibility loci: on chromosome 4p14 (rs1487630, P = 2.40 × 10(-11); odds ratio, 1.33), and in the SLC25A15-ELF1-WBP4 region on 13q14 (rs7329174 in ELF1, P = 5.12 × 10(-9); odds ratio, 1.27).

CONCLUSIONS

In a genome-wide association study, we identified 2 new susceptibility loci for Crohn's disease in a Japanese population. These findings could increase our understanding of the pathogenesis of Crohn's disease.

B cells secrete eotaxin-1 in human inflammatory bowel disease

BACKGROUND

Our previous studies have demonstrated that B cells in human inflammatory bowel disease (IBD) are highly activated and produce copious amounts of chemokines. Here, we showed that B cells produce eotaxin-1, a selective chemokine for acute eosinophilia. Increased levels of activated eosinophils have been found in the intestinal mucosa in patients with IBD, but their role(s) and the regulation of their migration patterns remain poorly defined.

METHODS

To determine how B-cell secretion of eotaxin-1 influences eosinophil activation and migration, we performed immunoepidemiological approaches coupled with in vitro studies. B cells and eosinophils from patients with Crohn's disease and ulcerative colitis were isolated, and responses to Toll-like receptor ligands (TLR) were measured and assessed for the relationship with clinical disease.

RESULTS

Eotaxin-1 from recirculating B cells, and TLR ligands, regulated eosinophil homing mechanisms in IBD. B cells stimulated with hypo-acylated lipopolysaccharide (LPS) produced copious amounts of eotaxin-1, which influenced eosinophil activation profiles in the bloodstream. We also found that hexa-acylated LPS, such Escherichia coli LPS, directly activated TLR2-expressing and TLR4-expressing eosinophils from patients with IBD to express a different repertoire of mucosal homing receptors, namely CCR9 and CCR10. Whereas B-cell production of eotaxin-1 was correlated with reduced disease activity, eosinophil activation by hexa-acylated LPS was associated with increased disease activity.

CONCLUSIONS

These results suggest that systemic TLR ligands influence eosinophil migration patterns, both directly and indirectly, through B cells. Our report uncovers unexpected mechanisms of cross talk between certain immune cells that shed new light on IBD immunology.

Population genetic tools for dissecting innate immunity in humans

Innate immunity involves direct interactions between the host and microorganisms, both pathogenic and symbiotic, so natural selection is expected to strongly influence genes involved in these processes. Population genetics investigates the impact of past natural selection events on the genome of present-day human populations, and it complements immunological as well as clinical and epidemiological genetic studies. Recent data show that the impact of selection on the different families of innate immune receptors and their downstream signalling molecules varies considerably. This Review discusses these findings and highlights how they help to delineate the relative functional importance of innate immune pathways, which can range from being essential to being redundant.

New genes and new insights from old genes: update on Alzheimer disease

PURPOSE OF REVIEW

This article discusses the current status of knowledge regarding the genetic basis of Alzheimer disease (AD) with a focus on clinically relevant aspects.

RECENT FINDINGS

The genetic architecture of AD is complex, as it includes multiple susceptibility genes and likely nongenetic factors. Rare but highly penetrant autosomal dominant mutations explain a small minority of the cases but have allowed tremendous advances in understanding disease pathogenesis. The identification of a strong genetic risk factor, APOE, reshaped the field and introduced the notion of genetic risk for AD. More recently, large-scale genome-wide association studies are adding to the picture a number of common variants with very small effect sizes. Large-scale resequencing studies are expected to identify additional risk factors, including rare susceptibility variants and structural variation.

SUMMARY

Genetic assessment is currently of limited utility in clinical practice because of the low frequency (Mendelian mutations) or small effect size (common risk factors) of the currently known susceptibility genes. However, genetic studies are identifying with confidence a number of novel risk genes, and this will further our understanding of disease biology and possibly the identification of therapeutic targets.

The microaerophilic microbiota of de-novo paediatric inflammatory bowel disease: the BISCUIT study

INTRODUCTION

Children presenting for the first time with inflammatory bowel disease (IBD) offer a unique opportunity to study aetiological agents before the confounders of treatment. Microaerophilic bacteria can exploit the ecological niche of the intestinal epithelium; Helicobacter and Campylobacter are previously implicated in IBD pathogenesis. We set out to study these and other microaerophilic bacteria in de-novo paediatric IBD.

PATIENTS AND METHODS

100 children undergoing colonoscopy were recruited including 44 treatment naïve de-novo IBD patients and 42 with normal colons. Colonic biopsies were subjected to microaerophilic culture with Gram-negative isolates then identified by sequencing. Biopsies were also PCR screened for the specific microaerophilic bacterial groups: Helicobacteraceae, Campylobacteraceae and Sutterella wadsworthensis.

RESULTS

129 Gram-negative microaerophilic bacterial isolates were identified from 10 genera. The most frequently cultured was S. wadsworthensis (32 distinct isolates). Unusual Campylobacter were isolated from 8 subjects (including 3 C. concisus, 1 C. curvus, 1 C. lari, 1 C. rectus, 3 C. showae). No Helicobacter were cultured. When comparing IBD vs. normal colon control by PCR the prevalence figures were not significantly different (Helicobacter 11% vs. 12%, p = 1.00; Campylobacter 75% vs. 76%, p = 1.00; S. wadsworthensis 82% vs. 71%, p = 0.312).

CONCLUSIONS

This study offers a comprehensive overview of the microaerophilic microbiota of the paediatric colon including at IBD onset. Campylobacter appear to be surprisingly common, are not more strongly associated with IBD and can be isolated from around 8% of paediatric colonic biopsies. S. wadsworthensis appears to be a common commensal. Helicobacter species are relatively rare in the paediatric colon.

TRIAL REGISTRATION

This study is publically registered on the United Kingdom Clinical Research Network Portfolio (9633).

Dynamic regulatory network controlling TH17 cell differentiation

Despite their importance, the molecular circuits that control the differentiation of naïve T cells remain largely unknown. Recent studies that reconstructed regulatory networks in mammalian cells have focused on short-term responses and relied on perturbation-based approaches that cannot be readily applied to primary T cells. Here, we combine transcriptional profiling at high temporal resolution, novel computational algorithms, and innovative nanowire-based tools for performing perturbations in primary T cells to systematically derive and experimentally validate a model of the dynamic regulatory network that controls Th17 differentiation. The network consists of two self-reinforcing, but mutually antagonistic, modules, with 12 novel regulators, whose coupled action may be essential for maintaining the balance between Th17 and other CD4+ T cell subsets. Overall, our study identifies and validates 39 regulatory factors, embeds them within a comprehensive temporal network and reveals its organizational principles, and highlights novel drug targets for controlling Th17 differentiation.

Pathogen-driven selection in the human genome

Infectious diseases and epidemics have always accompanied and characterized human history, representing one of the main causes of death. Even today, despite progress in sanitation and medical research, infections are estimated to account for about 15% of deaths. The hypothesis whereby infectious diseases have been acting as a powerful selective pressure was formulated long ago, but it was not until the availability of large-scale genetic data and the development of novel methods to study molecular evolution that we could assess how pervasively infectious agents have shaped human genetic diversity. Indeed, recent evidences indicated that among the diverse environmental factors that acted as selective pressures during the evolution of our species, pathogen load had the strongest influence. Beside the textbook example of the major histocompatibility complex, selection signatures left by pathogen-exerted pressure can be identified at several human loci, including genes not directly involved in immune response. In the future, high-throughput technologies and the availability of genetic data from different populations are likely to provide novel insights into the evolutionary relationships between the human host and its pathogens. Hopefully, this will help identify the genetic determinants modulating the susceptibility to infectious diseases and will translate into new treatment strategies.

Stories of love and hate: innate immunity and host-microbe crosstalk in the intestine

PURPOSE OF REVIEW

Recent advances in molecular techniques have enabled a deep view into the structure and function of the host's immune system and the stably associated commensal intestinal flora. This review outlines selected aspects of the interplay of innate immune recognition and effectors that shape the ecological niches for the intestinal microbiota.

RECENT FINDINGS

Several studies have demonstrated a pivotal role of innate immune receptor pathways (NOD-like receptors and Toll-like receptors) for the maintenance of microbial communities in the gut. Genetic deficiencies in these pathways have been associated with increased susceptibility to inflammation that in animal models can be transmitted via direct contact or by stool transplantation in the absence of abundant pathogens.

SUMMARY

The genetic architecture of the human host shapes the diversity and function of its stably associated intestinal microflora. Innate immune receptors such as NOD2 or the inflammasome component NOD-like receptor, pyrin-domain containing 6 play a major role in licensing the microbiota under physiological conditions. Understanding the symbiotic interplay in the intestinal tract should help develop procedures and therapeutic interventions aiming at the identification and restoration of disturbed microbiota states. Indeed, these states may be the missing trigger factor for the manifestation of a multitude of civilization disorders including inflammatory bowel disease and gastrointestinal cancer.

Clinical progress in the two years following a course of exclusive enteral nutrition in 109 paediatric patients with Crohn's disease

BACKGROUND

Exclusive enteral nutrition (EEN) is an effective first line treatment for active paediatric Crohn's disease (CD).

AIM

To examine the effect of EEN on short- and long-term clinical outcome together with anthropometric measurements.

METHODS

Retrospective case-note review in newly diagnosed CD (<16 years) who completed 8 weeks of EEN. Demographics, anthropometry, disease characteristics and inflammatory markers were collected at EEN initiation and at 1, 2, 6, 12 & 24 months post treatment initiation. EEN response was determined by a patient global assessment.

RESULTS

One hundred and nine patients were included (Males 68; Median age: 11.2 years). After 8 weeks EEN, 65 were in remission, 32 improved and 12 had no improvement. By 4 weeks, mean weight/BMI z-score (s.d.) increased (P < 0.02) and between 4 and 8 weeks (P < 0.05). Baseline inflammatory markers all improved significantly by week 4 (albumin, CRP and platelets; all P < 0.01) and ESR (P < 0.00001). 63/109(58%) relapsed during follow-up. 44/63(70%) patients completed a second course of EEN with similar response rate, but lower weight gain (3.3 vs. 5.1 kg, P < 0.05). Height z-score did not change significantly over the 24 months. Introduction of azathioprine within 6 months of diagnosis did not improve height outcomes at 24 months.

CONCLUSIONS

Weight and BMI z-score improved with EEN and changes are sustained to 2 years, but height z-score did not. Seventy per cent of patients who relapsed during 2-year follow-up managed a 2nd course of EEN. The optimal therapeutic strategies for length of EEN course and to improve linear growth are awaited.

Negative regulation of human mononuclear phagocyte function

At mucosal surfaces, phagocytes such as macrophages coexist with microbial communities; highly controlled regulation of these interactions is essential for immune homeostasis. Pattern-recognition receptors (PRRs) are critical in recognizing and responding to microbial products, and they are subject to negative regulation through various mechanisms, including downregulation of PRR-activating components or induction of inhibitors. Insights into these regulatory mechanisms have been gained through human genetic disease-association studies, in vivo mouse studies utilizing disease models or targeted gene perturbations, and in vitro and ex vivo human cellular studies examining phagocytic cell functions. Although mouse models provide an important approach to study macrophage regulation, human and mouse macrophages exhibit differences, which must be considered when extrapolating mouse findings to human physiology. This review discusses inhibitory regulation of PRR-induced macrophage functions and the consequences of dysregulation of these functions and highlights mechanisms that have a role in intestinal macrophages and in human macrophage studies.

Regulation of intestinal homeostasis and immunity with probiotic lactobacilli

The gut microbiota provide important stimuli to the human innate and adaptive immune system and co-mediate metabolic and immune homeostasis. Probiotic bacteria can be regarded as part of the natural human microbiota, and have been associated with improving homeostasis, albeit with different levels of success. Composition of microbiota, probiotic strain identity, and host genetic differences may account for differential modulation of immune responses by probiotics. Here, we review the mechanisms of immunomodulating capacities of specific probiotic strains, the responses they can induce in the host, and how microbiota and genetic differences between individuals may co-influence host responses and immune homeostasis.

Fecal calprotectin and clinical disease activity in pediatric ulcerative colitis

Objective. To explore fecal calprotectin levels in pediatric ulcerative colitis (UC) in relation with the validated clinical activity index PUCAI. Methods. This study included all 37 children (median age 14 years) with UC who had calprotectin measured (PhiCal ELISA Test) by the time of PUCAI assessment at the Children's Hospital of Helsinki in a total of 62 visits. Calprotectin values <100 μg/g of stool were considered as normal. The best cut-off value of each measure to predict 3-month clinical outcome was derived by maximizing sensitivity and specificity. Results. In clinically active disease (PUCAI ≥ 10), calprotectin was elevated in 29/32 patients (91% sensitivity). When in clinical remission, 26% (8/30) of the children had normal calprotectin but 7 (23%) had an exceedingly high level (>1000 μg/g). The best cut-off value for calprotectin for predicting poor outcome was 800 μg/g (sensitivity 73%, specificity 72%; area under the ROC curve being 0.71 (95%CI 0.57–0.85)) and for the PUCAI best cut-off values >10 (sensitivity 62%, specificity 64%; area under the ROC curve 0.714 (95%CI 0.58–0.85)). Conclusion. The clinical relevance of somewhat elevated calprotectin during clinical remission in pediatric UC is not known and, until further evidence accumulates, does not indicate therapy escalation.

Prostasin is required for matriptase activation in intestinal epithelial cells to regulate closure of the paracellular pathway

The type II transmembrane serine protease matriptase is a key regulator of epithelial barriers in skin and intestine. In skin, matriptase acts upstream of the glycosylphosphatidylinositol-anchored serine protease, prostasin, to activate the prostasin zymogen and initiate a proteolytic cascade that is required for stratum corneum barrier functionality. Here, we have investigated the relationship between prostasin and matriptase in intestinal epithelial barrier function. We find that similar to skin, matriptase and prostasin are components of a common intestinal epithelial barrier-forming pathway. Depletion of prostasin by siRNA silencing in Caco-2 intestinal epithelium inhibits barrier development similar to loss of matriptase, and the addition of recombinant prostasin to the basal side of polarized Caco-2 epithelium stimulates barrier forming changes similar to the addition of recombinant matriptase. However, in contrast to the proteolytic cascade in skin, prostasin functions upstream of matriptase to activate the endogenous matriptase zymogen. Prostasin is unable to proteolytically activate the matriptase zymogen directly but induces matriptase activation indirectly. Prostasin requires expression of endogenous matriptase to stimulate barrier formation since matriptase depletion by siRNA silencing abrogates prostasin barrier-forming activity. Active recombinant matriptase, however, does not require the expression of endogenous prostasin for barrier-forming activity. Together, these data show that matriptase and not prostasin is the primary effector protease of tight junction assembly in simple columnar epithelia and further highlight a spatial and tissue-specific aspect of cell surface proteolytic cascades.

Oxidative stress associated to dysfunctional adipose tissue: a potential link between obesity, type 2 diabetes mellitus and breast cancer

Diabetes mellitus and breast cancer are two important health problems. Type 2 diabetes (T2DM) and obesity are closely linked with both being associated with breast cancer. Despite abundant epidemiological data, there is no definitive evidence regarding the mechanisms responsible for this association. The proposed mechanisms by which diabetes affects breast cancer risk and prognosis are the same as the mechanisms hypothesised for the contribution of obesity to breast cancer risk. The obesity-induced inflammation promoted by adipose tissue dysfunction is a key feature, which is thought to be an important link between obesity and cancer. Inflammation induces an increase in free radicals and subsequently promotes oxidative stress, which may create a microenvironment favourable to the tumor development in obese persons. Oxidative stress is also proposed as the link between obesity and diabetes mellitus. Therefore, obesity-related oxidative stress could be a direct cause of neoplastic transformation associated with obesity and T2DM in breast cancer cells. This review is focused on the role of obesity-related oxidative stress in the context of chronic inflammation, on the time of breast cancer onset and progression, which provide targets for preventive and therapeutic strategies in the fields of diabetes and obesity-related breast cancer.

Epigenetics and the developmental origins of inflammatory bowel diseases

The gut microbiota, the intestinal mucosa and the host immune system are among the large biological networks involved in the development of inflammatory bowel disease (IBD), which includes Crohn disease (CD) and ulcerative colitis (UC). Host genetics and environmental factors can significantly modulate the interactive relationships among these biological systems and influence predilection toward IBD. High monozygotic twin discordance rates and the rapid rise in the prevalence of IBD indicate that environmental influences may be as important or even more important in their pathogenesis than genetic susceptibility. However, the nature and timing of environmental factors critical for inducing IBD remain largely unknown. The molecular mechanisms and the key biological component(s) that may be affected by such factors are also in question. Epigenetic changes, such as DNA methylation (the methylation of cytosines followed by a guanine in CpG dinucleotides) can be modified by environmental influences during finite developmental periods and have been implicated in the pathogenesis of IBD. Mucosal DNA methylation can also react to changes in the commensal microbiota, underscoring the intercalating relationships among the large biological systems involved in gastrointestinal disorders. Therefore, transient environmental influences during specific periods of development may induce critical change(s) in an isolated or concomitant fashion within the intestinal biomic networks and lead to increased susceptibility to IBD. The present review focuses on the emerging paradigm shift considering IBD to originate from critical environmental effects during pre- and postnatal development.

Gene expression and thiopurine metabolite profiling in inflammatory bowel disease - novel clues to drug targets and disease mechanisms?

BACKGROUND AND AIMS

Thiopurines are effective to induce and maintain remission in inflammatory bowel disease (IBD). The methyl thioinosine monophosphate (meTIMP)/6-thioguanine nucleotide (6-TGN) concentration ratio has been associated with drug efficacy. Here we explored the molecular basis of differences in metabolite profiles and in relation to disease activity.

METHODS

Transcriptional profiles in blood samples from an exploratory IBD-patient cohort (n = 21) with a normal thiopurine S-methyltransferase phenotype and meTIMP/6-TGN ratios >20, 10.0-14.0 and ≤4, respectively, were assessed by hybridization to microarrays. Results were further evaluated with RT qPCR in an expanded patient cohort (n = 54). Additionally, 30 purine/thiopurine related genes were analysed separately.

RESULTS

Among 17 genes identified by microarray-screening, there were none with a known relationship to pathways of purines/thiopurines. For nine of them a correlation between expression level and the concentration of meTIMP, 6-TGN and/or the meTIMP/6-TGN ratio was confirmed in the expanded cohort. Nine of the purine/thiopurine related genes were identified in the expanded cohort to correlate with meTIMP, 6-TGN and/or the meTIMP/6-TGN ratio. However, only small differences in gene expression levels were noticed over the three different metabolite profiles. The expression levels of four genes identified by microarray screening (PLCB2, HVCN1, CTSS, and DEF8) and one purine/thiopurine related gene (NME6) correlated significantly with the clinical activity of Crohn's disease. Additionally, 16 of the genes from the expanded patient cohort interacted in networks with candidate IBD susceptibility genes.

CONCLUSIONS

Seventeen of the 18 genes which correlated with thiopurine metabolite levels also correlated with disease activity or participated in networks with candidate IBD susceptibility genes involved in processes such as purine metabolism, cytokine signaling, and functioning of invariant natural killer T cells, T cells and B cells. Therefore, we conclude that the identified genes to a large extent are related to drug targets and disease mechanisms of IBD.

Expression of innate immune genes, proteins and microRNAs in lung tissue of pigs infected experimentally with influenza virus (H1N2)

This study aimed at providing a better understanding of the involvement of innate immune factors, including miRNA, in the local host response to influenza virus infection. Twenty pigs were challenged by influenza A virus subtype H1N2. Expression of microRNA (miRNA), mRNA and proteins were quantified in lung tissue at different time points after challenge (24 h, 72 h and 14 d post-infection (p.i.). Several groups of genes were significantly regulated according to time point and infection status including pattern recognition receptors (TLR2, TLR3, TLR7, retinoic acid-inducible gene I, melanoma differentiation associated protein-5), IFN and IFN-induced genes (IFN-β, IFN-γ, IRF7, STAT1, ISG15 and OASL), cytokines (IL-1 β, IL-1RN, IL-6, IL-7, IL-10, IL-12A, TNF-α, CCL2, CCL3 and CXCL10) and several acute phase proteins. Likewise, the following miRNAs were differentially expressed in one or more time groups compared with the control pigs: miR-15a, miR-21, miR-146, miR-206, miR-223 and miR-451. At d 1 p.i. lung tissue protein levels of IL-6, IL-12 and IFN-α were significantly increased compared with the control group, and haptoglobin and C-reactive protein were significantly increased at d 3 p.i. Our results suggest that, in addition to a wide range of innate immune factors, miRNAs may also be involved in controlling acute influenza infection in pigs.

DNA methylation analysis in the intestinal epithelium-effect of cell separation on gene expression and methylation profile

BACKGROUND

Epigenetic signatures are highly cell type specific. Separation of distinct cell populations is therefore desirable for all epigenetic studies. However, to date little information is available on whether separation protocols might influence epigenetic and/or gene expression signatures and hence might be less beneficial. We investigated the influence of two frequently used protocols to isolate intestinal epithelium cells (IECs) from 6 healthy individuals.

MATERIALS AND METHODS

Epithelial cells were isolated from small bowel (i.e. terminal ileum) biopsies using EDTA/DTT and enzymatic release followed by magnetic bead sorting via EPCAM labeled microbeads. Effects on gene/mRNA expression were analyzed using a real time PCR based expression array. DNA methylation was assessed by pyrosequencing of bisulfite converted DNA and methylated DNA immunoprecipitation (MeDIP).

RESULTS

While cell purity was >95% using both cell separation approaches, gene expression analysis revealed significantly higher mRNA levels of several inflammatory genes in EDTA/DTT when compared to enzymatically released cells. In contrast, DNA methylation of selected genes was less variable and only revealed subtle differences. Comparison of DNA methylation of the epithelial cell marker EPCAM in unseparated whole biopsy samples with separated epithelium (i.e. EPCAM positive and negative fraction) demonstrated significant differences in DNA methylation between all three tissue fractions indicating cell type specific methylation patterns can be masked in unseparated tissue samples.

CONCLUSIONS

Taken together, our data highlight the importance of considering the potential effect of cell separation on gene expression as well as DNA methylation signatures. The decision to separate tissue samples will therefore depend on study design and specific separation protocols.

Clinical utility of calprotectin and lactoferrin in patients with inflammatory bowel disease: is there something new from the literature?

The identification of noninvasive biomarkers is still one of the major issue for gastroenterologists dealing with inflammatory bowel disease patients, due to the chronicity of these conditions and the early onset of symptoms in the majority of cases. Research attention has focused mainly on fecal proteins, especially calprotectin and lactoferrin, and most of the published data are reassuring about their applicability in the diagnosis and monitoring of these patients. However, there are still pending questions regarding the reliability of fecal proteins especially in the era of mucosal healing and biologics.

Epidemiology of inflammatory bowel diseases: new insights from a French population-based registry (EPIMAD)

Most data regarding the natural history of inflammatory bowel diseases and their therapeutic management are from tertiary referral-centres. However, the patients followed in these centres represent a selected sample and extrapolation of these data to the general population is disputable. The EPIMAD Registry covers a large area of Northern France with almost 6 million inhabitants representing 9.3% of the entire French population. From 1988 to 2008, 18,170 incident patients were recorded in the registry including 8071 incident Crohn's disease, 5113 incident ulcerative colitis and 591 unclassified inflammatory bowel disease cases. The aim of this study was to review some of the most recent information obtained from this large population-based registry since its launch in 1988.

Disease phenotype at diagnosis in pediatric Crohn's disease: 5-year analyses of the EUROKIDS Registry

BACKGROUND

It has been speculated that pediatric Crohn's disease (CD) is a distinct disease entity, with probably different disease subtypes. We therefore aimed to accurately phenotype newly diagnosed pediatric CD by using the pediatric modification of the Montreal classification, the Paris classification.

METHODS

Information was collected from the EUROKIDS registry, a prospective, web-based registry of new-onset pediatric IBD patients in 17 European countries and Israel. When a complete diagnostic workup was performed (ileocolonoscopy, upper gastrointestinal [GI] endoscopy, small bowel imaging), CD patients were evaluated for ileocolonic disease extent, esophagogastroduodenal involvement, and jejunal/proximal ileal involvement. Disease behavior and the occurrence of granulomas were also analyzed.

RESULTS

In all, 582 pediatric CD patients could be classified according to the Paris classification. Isolated terminal ileal disease (± limited cecal disease) was seen at presentation in 16%, isolated colonic disease in 27%, ileocolonic disease in 53%, and isolated upper GI disease in 4% of patients. In total, 30% had esophagogastroduodenal involvement and 24% jejunal/proximal ileal disease. Patients with L2 disease were less likely to have esophagogastroduodenal involvement or stricturing disease than patients with L1 or L3 disease. Terminal ileal disease and stricturing disease behavior were more common in children diagnosed after 10 years of age than in younger patients. Granulomas were identified in 43% of patients.

CONCLUSIONS

Accurate phenotyping is essential in pediatric CD, as this affects the management of individual patients. Disease phenotypes differ according to age at disease onset. The Paris classification is a useful tool to capture the variety of phenotypic characteristics of pediatric CD.

Fecal transplant: a safe and sustainable clinical therapy for restoring intestinal microbial balance in human disease?

Recent studies have suggested an association between intestinal microbiota composition and human disease, however causality remains to be proven. With hindsight, the application of fecal transplantation (FMT) does indeed suggest a causal relation between interfering with gut microbiota composition and a resultant cure of several disease states. In this review, we aim to show the available evidence regarding the involvement of intestinal microbiota and human (autoimmune) disease. Moreover, we refer to (mostly case report) studies showing beneficial or adverse effects of fecal transplantation on clinical outcomes in some of these disease states. If these findings can be substantiated in larger randomized controlled double blind trials also implementing gut microbiota composition before and after intervention, fecal transplantation might provide us with novel insights into causally related intestinal microbiota, that might be serve as future diagnostic and treatment targets in human disease.

Genetics of inflammatory bowel diseases: a comparison between Western and Eastern perspectives

Inflammatory bowel disease (IBD) is a chronic relapsing intestinal inflammatory disorder with unidentified causes. Currently, studies indicate that IBD results from a complex interplay between various genetic and environmental factors that produce intestinal inflammation. However, these factors may differ for Asians and Caucasians. Thus, differences in epidemiology, genetic variants, and clinical phenotypes of IBD have been observed between the two populations. Understanding the discrepancies between data from populations with different genetic backgrounds and environmental factors may reveal fundamental aspects of IBD pathogenesis. Accordingly, this review will summarize the current knowledge of IBD genetics studied in Asian countries and compare it with that from Western countries, with special focus on innate bacterial sensing, autophagy, and the interleukin-23 receptor-T helper cell 17 pathway. The epigenetic nature of IBD pathogenesis as well as the pharmacogenetics related to the use of immunomodulators will also be briefly covered.

S100A12: a noninvasive marker of inflammation in inflammatory bowel disease

Inflammatory bowel diseases are incurable conditions that feature gut inflammation. Standard markers have inadequate sensitivity and specificity. S100A12 is a new fecal marker that has promise as a non-invasive indicator of gut inflammation. This article reviews recent studies focusing on S100A12 and highlights the current and potential roles of this biomarker.

Intestinal microbiota: a source of novel biomarkers in inflammatory bowel diseases?

The human intestine harbours a complex microbial ecosystem that performs manifold functions important to the nutrition and health of its host. Extensive study has revealed that the composition of the intestinal microbiota is altered in individuals with inflammatory bowel disease (IBD). The IBD associated intestinal microbiota generally has reduced species richness and diversity, lower temporal stability, and disruption of the secreted mucus layer structure. Multiple studies have identified certain bacterial taxa that are enriched or depleted in IBD including Enterobacteriaceae, Ruminococcus gnavus, and Desulfovibrio (enriched) and Faecalibacterium prausnitzii, Lachnospiraceae, and Akkermansia (depleted). Additionally, the relative abundance of some taxa appears to correlate with established markers of disease activity such as Enterobacteriaceae (enriched) and Lachnospiraceae (depleted). Signature shifts in fecal microbial community composition may therefore prove to be valuable as diagnostic biomarkers, particularly for longitudinal monitoring of disease activity and response to treatments.

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

Background & Aims

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

Methodology/Principal Findings

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

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

Conclusions/Significance

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

Endoplasmic reticulum aminopeptidase 1 and interleukin-23 receptor in ankylosing spondylitis

Endoplasmic reticulum aminopeptidase 1 (ERAP1) and interleukin-23 receptor (IL-23R) gene polymorphisms were found to be associated with ankylosing spondylitis (AS) in a nonsynonymous single nucleotide polymorphism association study, and this has been replicated in several studies across different populations. ERAP1 variants could lead to significant changes in the repertoire of peptides presented by MHC-I. Reading this in conjunction with the known association of AS with HLA-B27, a functional interaction between ERAP1 and HLA-B27 is very likely. ERAP1 has additionally been shown to be involved in cytokine receptor shedding. The IL-23R is one of the two receptors that mediate the action of IL-23. AS is associated with the same polymorphisms of IL-23R as those linked to psoriasis and inflammatory bowel disease. This suggests common genetic risks linking AS and extra-articular manifestations. This review focuses on the pathogenic potential of these two genes in AS.

Human metastable epiallele candidates link to common disorders

Metastable epialleles (MEs) are mammalian genomic loci where epigenetic patterning occurs before gastrulation in a stochastic fashion leading to systematic interindividual variation within one species. Importantly, periconceptual nutritional influences may modulate the establishment of epigenetic changes, such as DNA methylation at MEs. Based on these characteristics, we exploited Infinium HumanMethylation450 BeadChip kits in a 2-tissue parallel screen on peripheral blood leukocyte and colonic mucosal DNA from 10 children without identifiable large intestinal disease. This approach led to the delineation of 1776 CpG sites meeting our criteria for MEs, which associated with 1013 genes. The list of ME candidates exhibited overlaps with recently identified human genes (including CYP2E1 and MGMT, where methylation has been associated with Parkinson disease and glioblastoma, respectively) in which perinatal DNA methylation levels where linked to maternal periconceptual nutrition. One hundred 18 (11.6%) of the ME candidates overlapped with genes where DNA methylation correlated (r > 0.871; p < 0.055) with expression in the colon mucosa of 5 independent control children. Genes involved in homophilic cell adhesion (including cadherin-associated genes) and developmental processes were significantly overrepresented in association with MEs. Additional filtering of gene expression-correlated MEs defined 35 genes, associated with 2 or more CpG sites within a 10 kb genomic region, fulfilling the ME criteria. DNA methylation changes at a number of these genes have been linked to various forms of human disease, including cancers, such as asthma and acute myeloid leukemia (ALOX12), gastric cancer (EBF3), breast cancer (NAV1), colon cancer and acute lymphoid leukemia (KCNK15), Wilms tumor (protocadherin gene cluster; PCDHAs) and colorectal cancer (TCERG1L), suggesting a potential etiologic role for MEs in tumorigenesis and underscoring the possible developmental origins of these malignancies. The presented compendium of ME candidates may accelerate our understanding of the epigenetic origins of common human disorders.

M89V Sialic acid Acetyl Esterase (SIAE) and all other non-synonymous common variants of this gene are catalytically normal

Catalytically defective rare variants of Sialic acid Acetyl Esterase (SIAE) have previously been linked to autoimmunity. Studies presented here confirm that the M89V SIAE protein and all other products of common variant alleles of SIAE are catalytically normal. Although overexpressing transfected non-lymphoid cells secrete small amounts of SIAE that can associate with the cell surface, normal human lymphocytes do not exhibit cell surface SIAE, supporting genetic evidence in mice that indicates that this protein functions in a lymphocyte intrinsic manner. Analyses of the plasma proteome also indicate that SIAE is not secreted in vivo. A re-analysis exclusively of catalytically defective rare variant alleles of SIAE in subjects in which this gene was completely sequenced confirmed an association of SIAE with autoimmunity. A subset of catalytically defective rare variant SIAE alleles has previously been typed in a large genotyping study comparing a diverse group of disease subjects and controls; our re-analysis of this data shows that catalytically defective alleles are enriched in disease subjects. These data suggest that SIAE may be associated with autoimmunity and that further study of catalytically defective rare variant SIAE alleles in terms of autoimmune disease susceptibility is strongly warranted.

The cell biology of the intestinal epithelium and its relation to inflammatory bowel disease

The epithelial layer of our intestines must meet two opposing requirements. On one hand it must allow for efficient uptake of nutrients and fluids, on the other hand it is a vital defence barrier between the milieu interior and the milieu exterior. In contrast to the lung that by virtue of cilia movement is kept virtually sterile, the gut epithelium is confronted by a stupendous microbiological load and a substantial xenobiotic challenge. The efficiency by which our intestinal epithelium manages to deal with the challenge of efficient nutrient absorption while simultaneously fulfilling its barrier function is testimony to what the forces of evolution can accomplish. Importantly, our understanding as to how our gut epithelial compartment manages this balancing act is now rapidly emerging, answering one of the oldest questions in cell biology. Importantly, when aberrations in this balance occur, for instance as a consequence genetic polymorphisms, increased propensity to develop chronic inflammation and inflammatory bowel disease is the result. Thus the knowledge on intestinal cell biology and biochemistry is not only of academic interest but may also aid design of novel avenues for the rational treatment of mucosal disease.

Promises, delivery, and challenges of inflammatory bowel disease risk gene discovery

Over the past two decades, investigators have used whole genome linkage and genome-wide association studies, including the "Immunochip" study, to identify a surprising number (over 163) of genetic loci containing susceptibility genes for inflammatory bowel disease (IBD) and its 2 major phenotypes, Crohn's disease (CD) and ulcerative colitis (UC). These loci, although nearly all low-risk, have provided important lessons regarding the nature of IBD etiopathogenesis, including that most loci cause both CD and UC risk; one-third of loci have risk for other common autoimmune diseases; numerous loci contain genes that regulate immunity to microbes; Th17 cells are disproportionately influenced by genes within IBD loci; and the HLA region influences UC far greater than CD. Interleukin-10 receptor subunit (IL10RA and IL10RB) and IL10 cytokine gene mutations cause a rare, severe, infantile-onset, autosomal recessive CD, and this knowledge has allowed curative treatment by bone marrow transplant. Key tasks for broader clinical translation include discovery of risk variants for non-white populations; discovery of the less frequent but higher penetrance and familial risk variants by next-generation sequencing; and determining which of numerous associated variations within loci result in specific gene dysfunction causing IBD risk-as only a small number of genes within IBD loci, including NOD2, IL23R, ATG16L1, IRGM, and PTPN22 have specific functional variations characterized. Studying the effect of IBD susceptiblity gene dysfunctions in tissue cultures and animal models will allow the ultimate translational benefits of developing novel treatments for and potentially preventing IBD in those having specific genetic risk factors.

Modulating the human gut microbiome as an emerging therapeutic paradigm

The human body is actually a vast and changing ecosystem comprised of billions of microbial organisms, known collectively as the microbiome. Within the last few years, the study of the microbiome and its impact on human health has been a rapidly growing area of biomedical science. The gut intestinal tract microbiome has been a particular focus of research given its potential role in many inflammatory and metabolic diseases as well as drug metabolism. Although a nascent field, the potential for modulating the gut microbiome or human host interactions associated with these microbes offers new therapeutic strategies for many chronic diseases, in particular obesity, diabetes and inflammatory bowel diseases. Here we provide an overview of present knowledge about the gut microbiome, its putative role in metabolic diseases and the potential for microbiome focused treatments from the drug development perspective.

The organisation and structure of inflammatory bowel disease services for children and young people in the UK in 2010: significant progress but still room for improvement

BACKGROUND

Inflammatory bowel disease (IBD) is becoming more common in children. While treatment options remain limited the appropriate organisation and delivery of services are an integral part of good care.

METHODS

All eligible UK paediatric sites were invited to submit data for organisation of paediatric IBD services as of 1 September 2010. Comparison, when relevant, was made with the previous paediatric audit (2008) and the concurrently running adult audit.

RESULTS

24/25 (96%) of sites submitted data. The median number of patients managed and the median number of new IBD (ulcerative colitis and Crohn's disease only) cases per annum was 178 (IQR 136-281) and 32 (IQR 23-50), respectively. There was an increase in the IBD workforce including whole-time equivalent (WTE) IBD nurses (1.0 vs 1.5 WTE nurses, p=0.02). 1023 patients 16 years and younger were looked after in the 202 adult sites who submitted data; only 78/202 sites indicated they cared for 16-year-old and younger children; approximately half of these 78 sites had age-appropriate support facilities. Most paediatric sites have access to urgent endoscopy (83%), telephone advice (100%) and urgent clinic appointments (91%). Most sites did not have: shared care pathways with primary care (74%), annual reviews (71%), real time patient management systems (83%) and research network trial participation (78%).

CONCLUSIONS

Many aspects of paediatric IBD care in the UK are good and have shown significant improvement over recent years. There are areas in need of further change and specific regional and national action plans should address identified deficiencies before any future audit of paediatric and adult IBD services.

Serum infliximab concentrations in pediatric inflammatory bowel disease

OBJECTIVE

To study serum infliximab (s-IFX) levels in pediatric patients with inflammatory bowel disease (IBD).

SUBJECTS AND METHODS

s-IFX trough levels were measured in a total of 133 blood samples of 37 pediatric IBD patients (Crohn's disease, 23): 48 during the induction phase (weeks 2 and 6) and 85 during maintenance treatment. Antibodies to infliximab (ATI) were determined in 93 samples (30 patients). s-IFX values were related to fecal calprotectin (FC) and serum markers of inflammation.

RESULTS

During induction (5 mg/kg) and maintenance therapy, the median s-IFX levels were 17.6 μg/ml (range 0-48 μg/ml) and 3.55 μg/ml (range 0-40 μg/ml), respectively. The IFX levels were similar in ulcerative colitis and Crohn's disease (e.g. during maintenance median 3.2 vs. 2.8 μg/ml, p = 0.718), thus the data are pooled. During induction, the s-IFX level was associated with the total dose of IFX, that is, young children with lower body weight had lower levels (p < 0.001 at week 2 and p < 0.05 at week 6). Shorter administration interval resulted in higher trough levels (p < 0.005). All samples with undetectable s-IFX (6.8%) levels presented ATI. High inflammation (FC >1000 µg/g) during induction was associated with lower s-IFX levels (median 4.0 μg/ml, range 0.47-25 compared to median 20 μg/ml, range 0-48 when FC <1000 µg/g, p < 0.005). There was no significant association between the ESR or values of C-reactive protein and s-IFX levels during induction.

CONCLUSIONS

In pediatric IBD, lower body weight and higher level of intestinal inflammation are associated to s-IFX levels during induction but relation to therapeutic response is unclear.