There were no differences in small intestinal or colonic permeability. In parents, controllingfor age, sex, and family, there were no differences in baseline GIPerm. In contrast, controllingfor baseline value, age, sex, and family, after ibuprofen administration GIPerm increasedmore in the parents of FAP/IBS children than in the Control parents (day/evening Gastric:0.14 ± 1.22 vs. 0.04 ± 1.28, respectively, P<0.0005; Proximal: 2.28 ± 1.47 vs. 0.34 ± 1.43,P=0.001). Similar differences were noted for the 24 hr period. Small intestinal and colonicpermeability were similar between parent groups. Conclusions: Compared to Controls: 1)Siblings of children with FAP/IBS have evidence of increased gastric and proximal smallbowel permeability and 2) Parents of children with FAP/IBS respond to ibuprofen administra-tion with a greater increase in GIPerm than Control parents; 3) Use of extended collectionperiods increases the ability to detect differences in GIPerm.

1000

Transcriptional and Proteomic Profiling of the Intestinal Mucosa of Diarrhea-IBS Patients Reveals Enhanced Active Cellular Pathways Compared to HealthySubjectsCristina Martinez, Maria Vicario, Beatriz Lobo, Jose L. Mosquera, Laura Ramos, CarmenAlonso, Mar Guilarte, Ines de Torres, Esteban Saperas, Javier Santos

Background & Aims: Micro-inflammation and gut dysfunction are features of diarrhea-IBS(d-IBS) patients, although the underlying interacting molecular mechanisms remain mostlyunknown. Therefore, we aimed to identify critical networks and signaling pathways activein chronic diarrhea-associated inflammation. Methods: Healthy volunteers (n=18, 8 men)and age-matched (range, 21-62y) non-allergic, non-celiac naïve participants fulfilling d-IBSRome II (n=18, 7 men) were studied. Jejunal biopsies, obtained by Watson's capsule, weresubjected to chip analysis (Affymetrix Human Genome U133 Plus 2.0 GeneChips) andvalidation by Real-Time PCR, and proteomic analysis (DIGE) and spot identification byMALDI-TOF mass spectrometry. Gene and protein expression profiles were then evaluatedusing the Ingenuity Pathway Analysis software to detemine the biological networks, functionsand pathways most significant to those profiles. Results: 379 transcripts were differentiallyexpressed (p<0.05) between healthy and d-IBS (top gene changes are shown in table 1).Further insight revealed tight junction signaling (p=0.00143), caveolae-mediated endocytosis(p=0.0029) and PTEN signaling (p=0.00642) as the top canonical pathways differentiallyactive in d-IBS. Likewise, the proteomic analysis revealed 139 protein spots differentiallyexpressed (p<0.05) between groups. Interestingly, two concordant networks (score>30, p<1-30) of potentially interacting genes and proteins implicated in the significant biologicalfunctions of cellular assembly and organization and cell-to-cell signaling and interactionwere identified in d-IBS. Conclusion: Substantial differences in gene and protein expressionexist between healthy and d-IBS jejunal mucosa. Building networks of interactions betweendifferentially expressed transcripts seems a helpful and innovative approach to decipher thecomplex interplay regulating mucosal inflammation and may provide novel comprehensivetherapeutic and diagnostic targets for IBS.Top 20 differentially expressed genes in jejunal mucosal biopsy specimens from d-IBSpatients compared to healthy individuals.

A-155 AGA Abstracts

1001

Fine Mapping of the Genetic Risk Factors for Post-Infectious Irritable BowelSyndrome (PI-IBS) in the Walkerton Outbreak of Waterborne Gastroenteritis(GE)Alexandra-Chloe Villani, Mathieu Lemire, Marroon Thabane, Stephen M. Collins, John K.Marshall, Denis Franchimont

Background & Aim: We have previously screened 78 known functional variants (related tothe serotoninergic, intestinal epithelial barrier, and innate immunity pathways) and identified4 promoter and coding SNPs in the TLR9, IL6, and CDH1 regions associated with PI-IBSsusceptibility1 in the well-defined Walkerton Health study cohort.2 We aimed at betterdefining these associations by performing thorough fine mapping in these 3 regions andfunctional experiments. Methods: We used a pairwise tagging approach to select 63 SNPsthat were genotyped using Sequenom hME assays. The design also included SNPs in codingand predicted regulatory regions. Analysis compared subjects who experienced GE but didnot develop PI-IBS (889 controls) to those who experienced GE and reported PI-IBS 2-3years after the outbreak (228 cases). Associations between genetic variants and PI-IBS, orrelated traits, were assessed using mixed effects logistic regression models. Quantitative RT-PCR and sequencing methods were used to assess gene-expression correlation in monocytesderived from 32 healthy individuals. We evaluated associations using linear regressionstatistic. Results: We observed 1 novel independent association in IL6 (rs2069861: p=0.0079)and 14 additional associations (i.e. 6 in TLR9, 3 in IL6, 4 in CDH1) that can be explainedby the linkage disequilibrium with the 4 original variants. All SNPs were more significantlyassociated in the clinically confirmed GE subgroup (p as low as 2.6x10-4). We also evaluatedand concluded that all the identified susceptibility variants in the TLR9, IL6, and CDH1regions were independent risk factors for developing PI-IBS when compared to the previouslyidentified clinical risk factors, including younger age, female gender, bloody stools, abdominalcramps, weight loss, and prolonged diarrhea.2 We observed a significant association betweenIL6 mRNA level and genotypes of rs2069861 (p=0.0366), with carrier of the risk allele beingassociated with the highest level of IL6 mRNA expression. Conclusion: This study establishesthe first pillars of the genetic architecture of PI-IBS by demonstrating that variants in these3 genes all contribute to PI-IBS susceptibility, and are all independent risk factors fordeveloping PI-IBS when controlling for previously reported PI-IBS clinical risk factors inthe Walkerton population.2 These results indicate abnormalities in genes encoding epithelialbarrier functions and innate immune responses to enteric bacteria, and suggest a geneticcontribution to the development of IBS following acute GE. References: 1-Gastroenterology2008;134(4):Suppl 1:A122. 2-Gastroenterology 2006;131:445-450.

1002

The Role of 5-HTT LPR and Gnβ3 825c>T Polymorphisms and Gene-Environment Interactions in Irritable Bowel Syndrome (IBS)Yuri A. Saito, Joseph J. Larson, Elizabeth J. Atkinson, Brooke L. Fridley, JaniceZimmerman, Ann E. Almazar Elder, Gloria M. Petersen, Nicholas J. Talley

Background: Family/twin studies support the hypothesis that IBS is the result of genes andenvironment. Smaller studies have evaluated the role of SLC6A4 5-HTT LPR and GNβ3825C>T polymorphisms in IBS, and gene-environment interactions between the 5-HTT LPRpolymorphism with trauma have also been reported in the psychiatric literature, but gene-environment studies in IBS to date are lacking. Specific Aims: To assess the association ofthe two polymorphisms with IBS and age of onset, and to assess whether there were significantgene-environment interactions with IBS. Methods: Outpatients with IBS and matched controlscompleted a bowel questionnaire and provided blood for DNA for PCR-based genotyping.Genotype/allele frequencies were generated for each variant, with comparisons between casesand controls performed with logistic regression. Linear regression was used to evaluate theassociation between the variants and age of onset. Environmental variables tested includedabuse, parental alcohol abuse, parental psychiatric disorders, and gastrointestinal infections.Results: Genotyping was performed in 312 cases and 242 controls. The median age for casesand controls was 49.8 yrs (range: 18.0-70.0), and consisted of 433 (78%) females; 539(98%) were Caucasian. No differences between the two groups were observed for age andrace; cases were more likely to be female (86% v. 69%, p<0.001). The distribution of IBSsubtypes among cases was: 88 (28%) D-IBS, 28 (9%) C-IBS, 104 (33%) M-IBS, 92 (29%)other. No association was observed between IBS and both variants, irrespective of geneticmodel tested, nor did the variants predict age of onset of IBS. Significant gene-environmentinteractions were observed between GI infection and the 825T allele. For those reportingprevious gastrointestinal infection, the OR for IBS was 3.9 (95%CI: 1.2-12.8) whereas theOR was 0.82 (95% CI: 0.62-1.09) for those without prior infection, using an additive geneticmodel with gender, abuse, and parental psychiatric disorders as covariates. Similarly, therewas a significant interaction between infection and the 5-HTT LPR polymorphism, althoughthe amount of variability explained by these variables was low (R2=0.02). None of the otherenvironmental variables interacted with either genetic variant to predict IBS or IBS age ofonset. Conclusions: We did not observe an association between two functional variants onthe SLC6A4 and GNβ3 genes and IBS. However, there was a significant interaction betweenboth polymorphisms and infection in the development of IBS, suggesting that its etiologyis the result of a combination of specific genetic and environmental risk factors. DK066271.

1003

A Coding Variant in the Serotonin Receptor 3C Subunit Is Associated withDiarrhea-Predominant Irritable Bowel SyndromeJohannes Kapeller, Lesley A. Houghton, Jutta Walstab, Heinz Boenisch, Gudrun Rappold,Beate Niesler

Background & Aims: Serotonin type 3 (5-HT3) receptors are ligand-gated ion channels. Todate, five 5-HT3 receptor subunits A, B, C, D and E are known forming pentameric receptorsof diverse structure and function. 5-HT3 receptors are involved in the regulation of gutmotility, visceral sensation and secretion. 5-HT3 receptor antagonists are beneficial in somebut not all patients with diarrhea-predominant irritable bowel syndrome (IBS-D). As we

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