The genetics of irritable bowel syndrome

Gender-specific insights into the irritable bowel syndrome pathophysiology. Focus on gut dysbiosis and permeability

Irritable bowel syndrome (IBS) is the most common functional gastrointestinal disorder involving the brain-gut interaction. IBS is characterized by persistent abdominal pain and changes in bowel habits. IBS exerts significant impacts on quality of life and imposes huge economic costs. Global epidemiological data reveal variations in IBS prevalence, both globally and between genders, necessitating comprehensive studies to uncover potential societal and cultural influences. While the exact pathophysiology of IBS remains incompletely understood, the mechanism involves a dysregulation of the brain-gut axis, leading to disturbed intestinal motility, local inflammation, altered intestinal permeability, visceral sensitivity, and gut microbiota composition. We reviewed several gender-related pathophysiological aspects of IBS pathophysiology, by focusing on gut dysbiosis and intestinal permeability. This perspective paves the way to personalized and multidimensional clinical management of individuals with IBS.

Efficacy and safety of probiotics in irritable bowel syndrome: A systematic review and meta-analysis

BACKGROUND

Irritable bowel syndrome (IBS) is a common gastrointestinal disease characterized by abdominal pain, distension, and altered bowel habits. Probiotics may alleviate IBS symptoms, but clinical trials remain conflicting.

AIMS

To conduct a systematic review and meta-analysis of clinical trials to evaluate the efficacy and safety of probiotics for IBS patients.

METHODS

We searched relevant trials in PubMed, Web of Science, Embase, Cochrane Library, and Google Scholar from 2000 to June 2023. Standardized mean difference (SMD) and 95% confidence interval (CI) were calculated for continuous outcomes. A risk ratio (RR) and a 95% CI were calculated for dichotomous outcomes.

RESULTS

A total of 20 studies involving 3011 patients were obtained. The results demonstrated that probiotics are more effective than placebo in reducing global IBS symptoms improvement rate (RR = 1.401, 95% CI 1.182-1.662, P < 0.001) and quality of life scores (SMD = 0.286, 95% CI = 0.154-0.418, P < 0.001). Subgroup analyses showed that a shorter treatment time (less than eight weeks) could reduce distension scores (SMD = 0.197, 95% CI = 0.038-0.356, P = 0.015). High doses (daily dose of probiotics ≥ 10ˆ10) or multiple strains of probiotics exhibit beneficial effects on abdominal pain (SMD = 0.412, 95% CI = 0.112-0.711, P = 0.007; SMD = 0.590, 95% CI = 0.050-1.129, P = 0.032; respectively). However, there was no significant benefit on global symptom scores (SMD = 0.387, 95% CI 0.122 to 0.653, P = 0.004) with statistically high inter-study heterogeneity (I2 = 91.9%, P < 0.001). Furthermore, there was no significant inter-group difference in terms of adverse events frequency (RR = 0.997, 95% CI 0.845-1.177, P = 0.973).

CONCLUSION

Probiotics are effective and safe for IBS patients. High doses or multiple probiotic strains seem preferable, but definite conclusions are challenging due to the high heterogeneity. Large-scale, well-designed, and rigorous trials are needed to confirm their effectiveness.

Bibliometric analysis of the 100 most-cited papers about the role of gut microbiota in irritable bowel syndrome from 2000 to 2021

AIM

Over the last few decades, gut microbiota research has been the focus of intense research and this field has become particularly important. This research aimed to provide a quantitative evaluation of the 100 most-cited articles on gut microbiota and IBS and highlight the most important advances in this field.

METHODS

The database Web of Science Core Collection was used to download the bibliometric information the top 100 most-cited papers. Microsoft Excel 2021, CiteSpace, VOSviewer, R software, and an online analytical platform ( https://bibliometric.com/ ) were was applied to perform bibliometric analysis of these papers.

RESULTS

The total citation frequency in the top 100 article ranged from 274 to 2324, with an average citation of 556.57. A total of 24 countries/regions made contributions to the top 100 cited papers, and USA, Ireland, and China were the most top three productive countries. Cryan JF was the most frequently nominated author, and of the top 100 articles, 20 listed his name. Top-cited papers mainly came from the Gastroenterology (n = 13, citations = 6373) and Gut (n = 9, citations = 3903). There was a significant citation path, indicating publications in molecular/biology/immunology primarily cited journals in molecular/biology/genetics fields. Keywords analysis suggested that the main topics on gut microbiota and IBS were mechanisms of microbiome in brain-gut axis." Behavior" was the keyword with the strongest burst strength (2.36), followed by "anxiety like behavior" (2.24), "intestinal microbiota" (2.19), and "chain fatty acid" (1.99), and "maternal separation" (1.95).

CONCLUSION

This study identified and provided the bibliometric information of the top 100 cited publications related to gut microbiota and IBS. The results provided a general overview of this topic and might help researchers to better understand the evolution, Influential findings and hotspots in researching gut microbiota and IBS, thus providing new perspectives and novel research ideas in this specific area.

Gluten-free Diet Reduces the Risk of Irritable Bowel Syndrome: A Mendelian Randomization Analysis

Background: Whether a gluten-free diet (GFD) is a cause of irritable bowel syndrome (IBS) remains controversial. We aim at exploring the causal relationship between gluten intake and IBS within Mendelian randomization (MR) design. Methods: We conducted a two-sample MR and selected single-nucleotide polymorphisms (SNPs) associated with GFD as instrumental variables (IVs). SNPs and genetic associations with GFD and IBS were obtained from the latest genome-wide association studies (GWAS) in Europeans (GFD: cases: 1,376; controls: 63,573; IBS: cases:1,121; controls: 360,073). We performed inverse variance weighting (IVW) as the primary method with several sensitivity analyses like MR-Egger and MR-PRESSO for quality control. The above analyses were re-run using another large dataset of IBS, as well as changing the p-value threshold when screening IVs, to verify the stability of the results. Results: The final estimate indicated significant causal association [per one copy of effect allele predicted log odds ratio (OR) change in GFD intake: OR = 0.97, 95% confidence interval (CI) 0.96 to 0.99, p < 0.01] without heterogeneity statistically (Q = 2.48, p = 0.78) nor horizontal pleiotropy biasing the causality (p = 0.92). Consistent results were found in validation analyses. Results of MR Steiger directionality test indicated the accuracy of our estimate of the causal direction (Steiger p < 0.001). Conclusion: GFD might be a protective factor of IBS. Therefore, we suggest taking a diet of lower gluten intake into account in IBS prevention and clinical practice.

Bile Acid Diarrhea and NAFLD: Shared Pathways for Distinct Phenotypes

Irritable bowel syndrome with diarrhea (IBS-D) and NAFLD are both common conditions that may be influenced by shared pathways of altered bile acid (BA) signaling and homeostatic regulation. Pathophysiological links between IBS-D and altered BA metabolism include altered signaling through the ileal enterokine and fibroblast growth factor 19 (FGF19) as well as increased circulating levels of 7α-hydroxy-4-cholesten-3-one, a metabolic intermediate that denotes increased hepatic BA production from cholesterol. Defective production or release of FGF19 is associated with increased BA production and BA diarrhea in some IBS-D patients. FGF19 functions as a negative regulator of hepatic cholesterol 7α-hydroxylase; therefore, reduced serum FGF19 effectively de-represses hepatic BA production in a subset of IBS-D patients, causing BA diarrhea. In addition, FGF19 modulates hepatic metabolic homeostatic response signaling by means of the fibroblast growth factor receptor 4/klotho beta receptor to activate cascades involved in hepatic lipogenesis, fatty acid oxidation, and insulin sensitivity. Emerging evidence of low circulating FGF19 levels in subsets of patients with pediatric and adult NAFLD demonstrates altered enterohepatic BA homeostasis in NAFLD. Conclusion: Here we outline how understanding of shared pathways of aberrant BA homeostatic signaling may guide targeted therapies in some patients with IBS-D and subsets of patients with NAFLD.

Epidemiology of irritable bowel syndrome and its associated factors in Saudi undergraduate students

BACKGROUND/AIM

Irritable bowel syndrome (IBS) is common among undergraduate students and is associated with several modifiable risk factors. The present study aimed to explore the epidemiology of IBS in Saudi undergraduate students.

MATERIALS AND METHODS

A cross-sectional study was carried out from February 2018 to June 2018. A total of 767 undergraduate students from all regions of Saudi Arabia completed an online self-administered questionnaire. IBS symptoms were assessed using the Rome IV diagnostic criteria.

RESULTS

The mean age was 21.88 years (range 18-29); 56.1% of the study population were females and 50.1% were from the central region of Saudi Arabia. Students of medical colleges represented 30.2% of the sample. The overall prevalence of IBS was 15.8%. Significant independent risk factors for IBS were female sex (OR = 3.738; 95% CI = 2.093, 6.673), being a student in a medical college (OR = 7.216; 95% CI = 4.438, 11.733), living in a rented apartment (OR = 6.752; 95% CI = 2.586, 17.627), living on campus (OR = 6.563; 95% CI = 2.138, 20.145), poor sleep quality (OR = 3.156; 95% CI = 1.850, 5.385), exercise (OR = 0.394; 95% CI = 0.193, 0.803), smoking (OR = 5.256; 95% CI = 2.841, 9.724), family history of IBS (OR = 1.641; 95% CI = 1.012, 2.661), and emotional stress (OR = 2.184; 95% CI = 1.375, 3.469).

CONCLUSION

Overall, 15.8% of participants in this study met the Rome IV criteria for IBS diagnosis. IBS was associated with several lifestyle factors, as well as family history and emotional stress.

Social learning pathways in the relation between parental chronic pain and daily pain severity and functional impairment in adolescents with functional abdominal pain

Having a parent with chronic pain (CP) may confer greater risk of persistence of CP from childhood into young adulthood. Social learning, such as parental modeling and reinforcement, represents one plausible mechanism for the transmission of risk of CP from parents to offspring. Based on a 7-day pain diary in 154 pediatric patients with functional abdominal CP, we tested a model in which parental CP predicted adolescents' daily average CP severity and functional impairment (distal outcomes) via parental modeling of pain behaviors and parental reinforcement of adolescent's pain behaviors (mediators) and adolescents' cognitive appraisals of pain threat (proximal outcome representing adolescents' encoding of parents' behaviors). Results indicated significant indirect pathways from parental CP status to adolescent average daily pain severity (b = 0.18, SE = 0.08, 95% confidence interval: 0.04-0.31, P = 0.03) and functional impairment (b = 0.08, SE = 0.04, 95% confidence interval: 0.02-0.15, P = 0.03) over the 7-day diary period via adolescents' observations of parent pain behaviors and adolescent pain threat appraisal. The indirect pathway through parental reinforcing responses to adolescents' pain did not reach significance for either adolescent pain severity or functional impairment. Identifying mechanisms of increased risk of pain and functional impairment in children of parents with CP ultimately could lead to targeted interventions aimed at improving functioning and quality of life in families with CP. Parental modeling of pain behaviors represents a potentially promising target for family-based interventions to ameliorate pediatric CP.

The Role of Dietary Approach in Irritable Bowel Syndrome

Irritable bowel syndrome (IBS) is a chronic functional disorder of the gastrointestinal tract and is one of the most frequent gastrointestinal diseases. In IBS multiple pathophysiological mechanisms including alterations in intestinal motility, permeability, nutrient absorption, and intestinal microbiota have been implicated. Foods are commonly reported by patients to be a trigger of symptoms and therefore are likely involved in the generation of symptoms in IBS. Among all possible therapeutic options, a first-line approach to IBS is dietary education and identification of foods potentially responsible for the onset or worsening of symptoms. Dietary approaches include reduction of gas-producing foods (i.e. fermentable oligo-, di-, and monosaccharides and polyols (FODMAPs)), lactose and gluten. Further studies are required to link the ultimate role of diets in different IBS subtypes.

Efficacy of bio-optimized extracts of turmeric and essential fennel oil on the quality of life in patients with irritable bowel syndrome

BACKGROUND

The use of herbal products to treat irritable bowel syndrome (IBS), a disease that frequently affects the quality of life (QoL), is still under evaluation. This open pilot study assessed the efficacy of bio-optimized extracts of turmeric and essential fennel oil (Enterofytol®) in IBS patients.

METHODS

A total of 211 patients (14% diarrhea-predominant, IBS-D; 24% constipation-predominant, IBS-C; 62% mixed, IBS-M) were enrolled by general practitioners and completed questionnaires measuring symptom severity and QoL before and after Enterofytol®, two capsules b.i.d. for one month, followed by two capsules q.d. for another month.

RESULTS

IBS severity index and QoL were inversely related. A significant reduction in the severity index and an improvement in QoL were evident following treatment in all IBS subgroups. IBS-D patients showed the worst clinical picture at entry, with the highest IBS severity index and the lowest QoL score, compared with IBS-C and IBS-M subtypes. IBS-D patients, however, also showed the most pronounced response to therapy, considering both scores. The improvement in the IBS severity index was independent of age and sex.

CONCLUSIONS

Results from this "real-life" study show that the combination of turmeric and essential fennel oil over two months improves both symptoms and QoL in IBS patients, irrespectively of age, sex, initial severity of symptoms and IBS-subtypes, suggesting a potential role for the natural treatment of IBS.

The Gut Microbiome in Irritable Bowel Syndrome and Other Functional Bowel Disorders

Emerging data from epidemiologic, microbiome, and physiology research in patients with functional bowel disorders (FBDs) provide evidence for a linkage between alterations in the intestinal microbiota and FBDs. However, currently most of the data is based on association studies, and the causality role of the microbiota in these disorders is not established. Growing evidence for compositional changes and the increasing recognition of the association between the intestinal microbiota and gut-brain functions that are relevant to the pathophysiology and/or clinical symptoms of FBDs have led to increased interest in manipulating the intestinal microbiota for the treatment of these disorders.

Irritable bowel syndrome and diet

Irritable bowel syndrome (IBS) is a chronic functional disorder of the gastrointestinal tract and is one of the most commonly diagnosed gastrointestinal diseases. The impact of IBS on the general population is large due to its high prevalence, suboptimal medical treatments and significant economic burden. The pathophysiology of IBS is complex and treatments are often symptom-specific. The most common therapeutic approaches for IBS include education and reassurance, lifestyles (especially nutrition-based interventions), peripherally acting medications (which typically target motility), centrally acting medications (which target visceral hypersensitivity and pain) and psychological interventions (which aim to reduce the effects of stress or symptom-specific anxiety). A beneficial dietary approach might include the following measures: a diet low in fermentable oligo-,di- and monosaccharides and polyols (FODMAPs), limitation or exclusion of gas-producing foods and/or lactose and gluten and fiber supplementation in selected cases. New therapeutic agents, namely nutraceutics, are also an interesting option in the management of IBS patients. This paper will focus on available dietary interventions for IBS and will review the evidence for nutrition-based therapies.

Probiotics in functional bowel disorders

Functional bowel disorders (FBDs) are the most common gastrointestinal (GI) disorders seen by gastroenterologists and primary care physicians. The disorders affect patients functioning and quality of life (QOL) and are associated with significant healthcare burden. The current theory regarding the development of FBDs suggests brain-gut axis dysfunctions associated abnormal GI motility and sensation. Recent data suggest that alterations in the intestinal microbiota may have a role in the pathogenesis of FBDs; or at least have the potential to affect intestinal functions that are thought to be relevant to the development of functional GI symptoms. This has led to growing interest of healthcare providers and patients in targeting the intestinal microbiota for the treatment of FBDs. In this article we discuss the potential role probiotic interventions in the treatment of FBDs. We review the evidence from pre-clinical and clinical studies and discuss the current recommendations for the use of probiotics for FBDs in clinical practice.

Gene polymorphisms associated with functional dyspepsia

Functional dyspepsia (FD) is a constellation of functional upper abdominal complaints with poorly elucidated pathophysiology. However, there is increasing evidence that susceptibility to FD is influenced by hereditary factors. Genetic association studies in FD have examined genotypes related to gastrointestinal motility or sensation, as well as those related to inflammation or immune response. G-protein b3 subunit gene polymorphisms were first reported as being associated with FD. Thereafter, several gene polymorphisms including serotonin transporter promoter, interlukin-17F, migration inhibitory factor, cholecystocynine-1 intron 1, cyclooxygenase-1, catechol-o-methyltransferase, transient receptor potential vanilloid 1 receptor, regulated upon activation normal T cell expressed and secreted, p22PHOX, Toll like receptor 2, SCN10A, CD14 and adrenoreceptors have been investigated in relation to FD; however, the results are contradictory. Several limitations underscore the value of current studies. Among others, inconsistencies in the definitions of FD and controls, subject composition differences regarding FD subtypes, inadequate samples, geographical and ethnical differences, as well as unadjusted environmental factors. Further well-designed studies are necessary to determine how targeted genes polymorphisms, influence the clinical manifestations and potentially the therapeutic response in FD.

Diagnosis of Irritable Bowel Syndrome: Role of Potential Biomarkers

Irritable bowel syndrome is a disorder diagnosed on symptom-based criteria without inclusion of any objective parameter measurable by known diagnostic methods. Heterogeneity of the disorder and overlapping with more serious organic diseases increase uncertainty for the physician's work and increase the cost of confirming the diagnosis. This paper is an attempt to summarize the efforts to find adequate biomarkers for irritable bowel syndrome, which should shorten the time to diagnosis and reduce the cost. Most of the reviewed papers were observational studies from secondary care institutions. Since publication of the Rome III criteria in 2006, most recent studies use these for the recruitment of IBS patients. This is a positive step forward as future studies should use the same criteria, facilitating comparison of their results. Among the studied biomarkers, most evidence is provided for fecal calprotectin. Cutoff values for fecal calprotectin have still to be investigated prior to inclusion in the irritable bowel syndrome diagnostic algorithm.

Systematic review with meta-analysis: post-infectious irritable bowel syndrome after travellers' diarrhoea

BACKGROUND

Gastrointestinal infection is known as a risk factor for the development of the irritable bowel syndrome (post-infectious irritable bowel syndrome, PI-IBS). The incidence of PI-IBS ranges between 3% and over 30% of people after infectious gastroenteritis.

AIM

To perform a meta-analysis pools and report data concerning the relative risk (RR) of PI-IBS after TD.

METHODS

Database search using Medline through PubMed, Scopus, EBM Reviews (Cochrane Database of Systematic Reviews) and PsycINFO was performed to identify relevant studies. Those that met the inclusion criteria were pooled. A random effects model (Mantel-Haenszel) was performed.

RESULTS

Six eligible studies were found. In three of six studies, the authors reported a statistically significant association of TD and PI-IBS. The pooled RR was 3.35 (95% CI: 2.22-5.05) with a significant overall effect (P < 0.00001). Overall PI-IBS incidence was 5.4% in TD subjects and 1.4% in healthy subjects. There was no significant heterogeneity within the pooled studies (I(2)  = 5%). Self-reported TD alone resulted in an over 1.5-fold RR for PI-IBS compared to laboratory-confirmed TD [RR 3.90 (95% CI: 2.35-6.49) vs. RR 2.42 (95% CI: 1.22-4.78)].

CONCLUSIONS

There is a strong association between travellers' diarrhoea and post-infectious irritable bowel syndrome. Self-reports of exposure seem to result in a higher post-infectious irritable bowel syndrome occurrence than laboratory-confirmed cases of travellers' diarrhoea, but further studies are needed to confirm this finding. Finally, potential influences of the selection of an appropriate study population on post-infectious irritable bowel syndrome epidemiology are discussed.

Irritable bowel syndrome: pathogenesis, diagnosis, treatment, and evidence-based medicine

Irritable bowel syndrome (IBS) is a chronic and debilitating functional gastrointestinal disorder that affects 9%-23% of the population across the world. The percentage of patients seeking health care related to IBS approaches 12% in primary care practices and is by far the largest subgroup seen in gastroenterology clinics. It has been well documented that these patients exhibit a poorer quality of life and utilize the health care system to a greater degree than patients without this diagnosis. The pathophysiology of IBS is not clear. Many theories have been put forward, but the exact cause of IBS is still uncertain. According to the updated ROME III criteria, IBS is a clinical diagnosis and presents as one of the three predominant subtypes: (1) IBS with constipation (IBS-C); (2) IBS with diarrhea (IBS-D); and (3) mixed IBS (IBS-M); former ROME definitions refer to IBS-M as alternating IBS (IBS-A). Across the IBS subtypes, the presentation of symptoms may vary among patients and change over time. Patients report the most distressing symptoms to be abdominal pain, straining, myalgias, urgency, bloating and feelings of serious illness. The complexity and diversity of IBS presentation makes treatment difficult. Although there are reviews and guidelines for treating IBS, they focus on the efficacy of medications for IBS symptoms using high-priority endpoints, leaving those of lower priority largely unreported. Therefore, the aim of this review is to provide a comprehensive evidence-based review of the diagnosis, pathogenesis and treatment to guide clinicians diagnosing and treating their patients.

Association of cannabinoid type 1 receptor and fatty acid amide hydrolase genetic polymorphisms in Chinese patients with irritable bowel syndrome

BACKGROUND AND AIM

The endocannabinoid system is involved in the pathophysiology of irritable bowel syndrome (IBS). Here, we investigated whether genetic variants of the cannabinoid type 1 receptor (CNR1) and fatty acid amide hydrolase (FAAH) are associated with the pathogenesis of IBS.

METHODS

In total, 292 patients with IBS and 298 healthy controls were enrolled. Polymerase chain reaction (PCR) and DNA sequencing were applied to determine the genotyping of polymorphic triplet AAT repeats located at the 3'-end of the CNR1 gene. The single nucleotide polymorphism (SNP) C385A at the FAAH gene (rs324420) was determined by PCR using TaqMan SNP Genotyping Assay Sets.

RESULTS

A total of eight alleles with AAT triplet repeats in the CNR1 gene were detected. The alleles were divided into two groups (≤ 10 and > 10) and three genotypes (≤ 10/≤ 10, ≤ 10/> 10, and > 10/> 10). The frequency of > 10 alleles was significantly higher in the IBS group (90.6%) when compared with the control group {81.7%, P < 0.001, odds ratio (OR) (95% confidence interval [CI]) = -0.128}. In addition, the genotypes > 10/> 10 were significantly associated with IBS (P < 0.001, OR [95% CI] = -0.163). The frequency of the A allele and the distribution of the AA genotype in the FAAH gene in the IBS group were not significantly different from those in the control group (P > 0.05), even though the frequency of the AA genotype was lower in the IBS group (1.0%) than that in the control group (3.4%, P = 0.089, OR [95% CI] = 3.345).

CONCLUSIONS

The variation in the (AAT)n repeat of the CNR1 gene conferred an increased risk for developing IBS, while rs324420 (C385) in the FAAH gene was not associated with IBS pathogenesis.

Association study of serotonin transporter SLC6A4 gene with Chinese Han irritable bowel syndrome

Objective

Irritable bowel syndrome (IBS) is a common clinical gastrointestinal dysfunction disorders. 5-sertonon (5-hydroxytryptamine, 5-HT) is a very important neurotransmitter, which is involved in gastrointestinal motion and sensation. Solute carrier family 6 member 4 (SLC6A4) gene encode serotonin transporter (SERT) which function is to rapidly reuptake the most of 5-HT. Therefore, it is needed to explore the association between SLC6A4 gene polymorphisms and IBS.

Methods

119 patients and 238 healthy controls were administrated to detect the SLC6A4 gene polymorphisms including 5-HT-transporter-gene-linked polymorphic region (5-HTTLPR), variable number of tandem repeats (VNTRs) and three selected tag Single Nucleotide Polymorphisms (SNPs) rs1042173, rs3794808, rs2020936 by using polymerase chain reaction (PCR) and TaqMan® SNP Genotyping.

Results

There were significant difference for 5-HTTLPR between IBS and control groups (X2 = 106.168, P<0.0001). In control group, genotypes were mainly L/L (58.4%), however, the genotypes in IBS were S/S (37.8%). The significant difference was shown in D-IBS subjects when compared to the controls (X² = 50.850, P<0.0001) for 5-HTTLPR. For STin2 VNTR, rs1042173, rs3794808, and rs2020936 polymorphisms, there were no any significant differences between IBS and control groups. There were no statistical significantly haplotypes for 5-HTTLPR, VNTRs and the three SNPs between IBS and controls.

Conclusion

The S allele in 5-HTTLPR was a susceptible allele with Chinese Han IBS, but other associations of VNTRs, three selected Tag SNPs and positive haplotype with IBS were not found. It is indicated that much research are needed to study the relationship between other polymorphisms in SLC6A4 gene and IBS.

Microbiota in health and irritable bowel syndrome: current knowledge, perspectives and therapeutic options

The gastrointestinal tract is a natural reservoir of microbiota. The gut is germ-free at birth, but rapidly becomes host to various bacteria establishing a progressively mutual relationship. The composition of gut microbiota is individual-specific and depends on the genotype of the host and environmental factors. Novel techniques have been used to characterize gastrointestinal microbiota, including genomic approaches. The bacterial profile shows that dominant and minor phyla are present in the gastrointestinal tract. From the proximal to the distal segments of the gut the bacterial density gradually increases, reaching an estimated 10(11) to 10(12) bacteria per gram of colonic content. Dynamic interactions between gut and microbiota play a physiological role in metabolic, protective and structural functions, while dysbiosis contributes to several diseases. Microbiota appear to play a role in IBS, where qualitative and quantitative changes of bacteriaoccur in IBS subtypes. Initial therapeutic approaches in IBS have focused on microbiota. The relationship between perturbations of the microbiota, mucosal inflammation and IBS remains to be further investigated.

The role of 5-HTT LPR and GNβ3 825C>T polymorphisms and gene-environment interactions in irritable bowel syndrome (IBS)

BACKGROUND

Smaller studies have evaluated SLC6A4 5-HTTLPR and GNβ3 825C>T polymorphisms in IBS, and interactions between 5-HTT LPR with life events have been reported in the psychiatric literature, but gene-environment studies in IBS are lacking.

AIMS

The purpose of this study was to assess the association of two polymorphisms with IBS and age of onset, and whether there are gene-environment interactions with IBS.

METHODS

Outpatients with IBS and controls completed a validated questionnaire and provided blood for DNA. Comparisons of genotype/allele frequencies between cases and controls were performed with logistic regression. Linear regression was used to evaluate the association between the variants and age of onset. Environmental variables tested included abuse, parental alcohol abuse, parental psychiatric disorders, and gastrointestinal infections.

RESULTS

Genotyping was performed in 385 cases and 262 controls with median age of 50 years (range, 18.0-70.0) and 498 (77 %) females. The IBS subtype distribution among cases was: 102 (26 %) D-IBS, 40 (10 %) C-IBS, 125 (32 %) M-IBS, 118 (31 %) other. No association was observed between IBS or age of onset and both variants. Significant interactions were observed between GI infection and the GNβ3 825T allele. For those reporting gastrointestinal infection, the OR for IBS was 3.9 (95 % CI 1.2-12.7) whereas the OR was 0.86 (95 % CI 0.65-1.13) for those without prior infection.

CONCLUSIONS

There was a significant interaction between the GNβ3 polymorphism and infection in the development of IBS, suggesting that its etiology is the result of a combination of specific genetic and environmental risk factors.

Sleep disruption secondary to overnight call shifts is associated with irritable bowel syndrome in residents: a cross-sectional study

OBJECTIVES

Sleep disruption has been associated with irritable bowel syndrome (IBS). We hypothesized that residents with greater sleep disruption secondary to intermittent overnight call shifts would have a higher prevalence of IBS.

METHODS

Postgraduate residents completed a Web-based survey including demographic data, frequency and characteristics of call shifts, the Rome III questionnaire, and the IBS-quality of life measure.

RESULTS

For every hour of sleep deprivation while on call vs. off call, the odds ratio for an increased likelihood of IBS was 1.32, after adjustment for age and gender. The mean number of calls per block, sleep deprivation while on call, and specialty program vs. family practice each predicted the severity of IBS.

CONCLUSIONS

Sleep disruption secondary to overnight call in residents was associated with an increased prevalence of IBS.

A cross-sectional study of the association between overnight call and irritable bowel syndrome in medical students

BACKGROUND

Shift work has been associated with irritable bowel syndrome (IBS), which includes gastrointestinal symptoms such as abdominal pain, constipation and diarrhea. Overnight call shifts also lead to a disruption of the endogenous circadian rhythm.

HYPOTHESIS

Medical students who perform intermittent overnight call shifts will demonstrate a higher prevalence of IBS symptoms when compared with medical students who perform no overnight call shifts.

METHODS

First- and second-year (preclinical) medical students have no overnight call requirements, whereas third- and fourth-year medical (clerkship) students do have overnight call requirements. All medical students at the Schulich School of Medicine and Dentistry (London, Ontario) were invited to complete an anonymous, web-based survey or an identical paper copy that included demographic data, the Rome III questionnaire and the IBS-Quality of Life measure (IBS-QOL). The prevalence of IBS symptoms and quality of life secondary to those symptoms were determined.

RESULTS

Data were available for 247 medical students (110 preclinical students, 118 clerkship students and 19 excluded surveys). There was no significant difference in the presence of IBS between preclinical and clerkship students (21 of 110 [19.1%] versus 26 of 118 [22.0%]; P=0.58). The were no significant differences in mean (± SD) IBS-QOL score of those with IBS between preclinical (43.5±8.3) and clerkship students (45.7±13.8) (P=0.53).

CONCLUSIONS

Participation in overnight call was not associated with the development of IBS or a lower quality of life secondary to IBS in medical students.

Irritable bowel syndrome among a cohort of European travelers to resource-limited destinations

BACKGROUND

Travelers' diarrhea (TD) remains a frequent travel-associated infection. Between 4 and 32% of enteric infections were followed by a postinfectious irritable bowel syndrome (pIBS) with long-term sequelae in various settings. Travel-related IBS incidence rates are based on small studies and IBS predictors have not been sufficiently evaluated.

METHODS

Adult travelers to resource-limited destinations participated in a prospective questionnaire-based cohort study. Demographics, travel characteristics, and medical history were assessed and those with functional or organic gastrointestinal disorders were excluded. Immediately after return from abroad, the volunteers completed a second questionnaire on TD, other health impairments, and on nutritional hygiene. Six-months post-travel, a follow-up questionnaire assessed IBS based on Rome III criteria. Risk factors were analyzed by multiple logistic regression.

RESULTS

Among a total of 2,476 subjects analyzed (participation rate 72.4%), 38 (1.5%) developed new IBS, and the 6-month incidence rate for pIBS was 3.0% (95% CI 1.9-4.2) following TD. Significant risk factors were TD during the surveyed journey (OR 3.7; 95% 1.8-7.4), an adverse life event experienced within 12 months pre-travel (OR 3.1; 1.4-6.8), and a diarrheal episode experienced within 4 months pre-travel (OR 2.7; 95% CI 1.3-5.6). Following multiple diarrheal episodes, the risk of acquiring IBS increased by six times.

CONCLUSIONS

In a large population of European travelers IBS had a lower incidence rate as compared to previous studies. Particular risk groups were identified; those may need to be protected.

Prevalence of irritable bowel syndrome (IBS) in first-degree relatives of patients with inflammatory bowel disease (IBD)

BACKGROUND

Epidemiological studies have shown a greater prevalence of irritable bowel syndrome (IBS) and inflammatory bowel disease (IBD) among first-degree relatives of patients diagnosed of these diseases. However, it is not known whether relatives of patients with IBD have a greater prevalence of IBS than the general population.

AIMS

To analyse the prevalence of IBS among first-degree relatives by consanguinity (parents, siblings and offspring) and affinity (spouses) of patients with IBD.

MATERIALS AND METHODS

A prevalence study was conducted identifying 490 relatives of 91 patients with IBD. Of these, 404 met inclusion criteria; and 360 (response rate: 89.1%) answered the questionnaires. Subjects were invited to participate in the study through index cases (patients with IBD). The following variables were collected: age, sex, history of digestive diseases, kinship and cohabitation with the index case. The relatives completed a questionnaire to identify those who met Rome I and Rome II criteria for IBS.

RESULTS

The overall prevalence of IBS among the first-degree relatives of patients with IBD was 49.4% and 10% according to Rome I and Rome II criteria respectively. IBS prevalence was higher in first-degree blood relatives than in spouses of patients (Rome I: 53.1% vs 29.1%, p=0.001; Rome II: 10.8% vs 5.4%, NS). No differences were found in IBS prevalence depending on whether relatives were living with the index case or not.

CONCLUSION

IBS prevalence in first-degree relatives of patients with IBD is elevated. It is significantly greater in blood relatives, which suggests involvement of genetic and psychological factors rather than environmental factors.

IBS: An epigenetic perspective

IBS is a common and debilitating disorder. The pathophysiology of IBS is poorly understood and is currently viewed as a biopsychosocial disorder with symptoms mediated via the brain-gut axis. Epidemiological studies of IBS point to risk factors such as familial clustering, sexual abuse and other forms of childhood trauma, low birth weight and gastrointestinal infection. Epigenetics focuses on the complex and dynamic interaction between the DNA sequence, DNA modifications and environmental factors, all of which combine to produce the phenotype. Studies in animal models of early stress and in humans who have experienced childhood trauma or abuse suggest that these events can lead to long-lasting epigenetic changes in the glucocorticoid receptor gene brought about by hypermethylation of a key regulatory component. Animal studies also indicate that the microbiota has a pivotal role in programming the core stress system, the hypothalamic-pituitary-adrenal axis and the immune system through epigenetic mechanisms. In this Perspectives, an epigenetic model of IBS is presented that incorporates many of the current findings regarding IBS, including proinflammatory markers, neuroendocrine alterations and links with both psychosocial stress and stress related to infection. We conclude that applying epigenetic methodology to this common and disabling disorder may help unravel its complex pathophysiology and lead to more effective treatments.

Current insights in to the pathophysiology of Irritable Bowel Syndrome

Irritable Bowel Syndrome (IBS) represents a functional disorder of gastrointestinal tract without the presence of an anatomic defect, in which abdominal pain is relieved with defecation and is associated with altered bowel habits.IBS includes a wide range of symptoms while its pathophysiology is very complicated. Recent studies indicate that the most important mechanisms include visceral sensitivity, abnormal gut motility and autonomous nervous system dysfunction. The interactions between these three mechanisms make bowel's function susceptible to many exogenous and endogenous factors like gastrointestinal flora, feeding and psychosocial factors. Recent data indicate that according to the above mechanisms, the influence of genetic factors and polymorphisms of human DNA in the development of IBS is equally important.

Familial aggregation of irritable bowel syndrome: a family case-control study

OBJECTIVES

Irritable bowel syndrome (IBS) clusters in families, but previous studies documented family history only from patients. We have shown that patient-relative agreement on IBS status is poor. Thus, we conducted a family case-control study with direct survey of symptoms from family members to better quantitate the aggregation of IBS in families. The aims of this study were to (i) compare the prevalence of IBS in case-relatives with control-relatives, and (ii) determine whether gender, relationship, predominant symptom, and environmental risk factors affect familial aggregation.

METHODS

Outpatients with IBS, matched controls, and their first-degree relatives completed a bowel symptom questionnaire. Percent of cases and controls with a family history were compared and odds ratios were computed using chi(2)-test; recurrence risks to relatives were computed using logistic regression and generalized estimating equations.

RESULTS

Data were collected from 477 cases, 297 controls, 1,492 case-relatives, and 936 control-relatives. Probands had a median age of 50 and 78% were women. 50% of case and 27% of control families had at least another relative with IBS yielding an odds ratio of 2.75 (95% CI: 2.01-3.76, P<0.0001). When aggregation estimates were reevaluated stratifying by relative relationship or proband gender, generational and gender effects were not observed. Familial clustering by bowel habit was weakest for diarrhea, and strongest for alternating bowel habits.

CONCLUSIONS

IBS aggregates strongly in families. The strength of the association does vary somewhat by relationship to proband, but the lack of association in spouses supports either a possible genetic etiology or a shared household environmental exposure as an underlying cause of IBS.

The serotonin transporter polymorphism rs25531 is associated with irritable bowel syndrome

Irritable bowel syndrome is a frequent gastrointestinal disorder of unknown etiology. The serotonin transporter regulates the intensity and duration of serotonin signaling in the gut and is, therefore, an attractive candidate gene for irritable bowel syndrome. Previous studies investigating the 5-HTTLPR and Stin2 VNTR polymorphisms of the serotonin transporter have proved inconclusive. In this exploratory study we therefore expanded the search for a possible association of the serotonin transporter with irritable bowel syndrome to include not only the 5-HTTLPR and Stin2 VNTR length polymorphisms, but also the functional single nucleotide polymorphism rs25531. We genotyped 186 patients with irritable bowel syndrome and 50 healthy control subjects raging in age from 18 to 70 years. Carriers of the rare G allele of rs25531 had approximately threefold increased odds of irritable bowel syndrome compared with healthy controls (OR 3.3, 95% CI 1.1-9.6). Our findings suggest that further investigation of the possible role of the serotonin transporter in the etiology of IBS is warranted.

Proinflammatory cytokine gene polymorphisms in irritable bowel syndrome

INTRODUCTION

Irritable bowel syndrome (IBS) is a multifactorial functional gastrointestinal disorder, characterized by recurrent abdominal pain and altered bowel habits. Proinflammatory cytokines can play an important role in intestinal inflammation, while their production is under genetic control.

METHODS

This study was performed in a group of patients with IBS to analyze the genotype frequencies of a number polymorphic genes coding for proinflammatory cytokine (interleukin-6 (IL), tumor necrosis factor-alpha (TNF-alpha), and IL-1 group). Using polymerase chain reaction with sequence-specific primers method, the cytokine genes were amplified, and alleles and genotypes of 71 patients with IBS were detected on gel electrophoresis, and the results were compared with healthy control subjects.

RESULTS

Results of the analyzed data showed that the frequencies IL-1R C allele at position Pst-I 1970 (P = 0.017), IL-6 G allele at position -174 (P = 0.002), and TNF-alpha G allele at position -238 (P < 0.001) in the patient group were significantly higher than the control group. IL-6 GG genotype (-174) and TNF-alpha GG genotype (-238) in the patient group were also significantly overrepresented (P < 0.001), while IL-6 CG genotype (-174) and TNF-alpha GA genotype (-238) were significantly decreased in the patients with IBS (P < 0.001). The frequencies of IL-6 (-174, nt565) GG haplotype and TNF-alpha (-308, -238) GG haplotype were also significantly higher in the patient group (P < 0.001), whereas the frequencies of the haplotypes IL-6 CG and TNF-alpha GA were significantly decreased in the patients with IBS (P < 0.001).

CONCLUSION

IL-6 and TNF-alpha proinflammatory cytokine gene polymorphisms could change individual susceptibility to IBS and might have a role in pathophysiology of disease.

Prevalence of functional gastrointestinal disorders in patients with fibromyalgia and the role of psychologic distress

BACKGROUND & AIMS

Fibromyalgia is a rheumatologic disorder associated with somatic and psychologic conditions. Although fibromyalgia is associated with irritable bowel syndrome, its relationship with other functional gastrointestinal disorders (FGID) is unclear. We evaluated the prevalence of FGID in patients with fibromyalgia and the role of psychologic factors in this relationship.

METHODS

From a Spanish population, 100 patients with fibromyalgia and 100 matched controls completed the Rome II Integrative Questionnaire to assess the prevalence of FGID and the Symptom Checklist-90 Revised (SCL-90R) to evaluate psychologic distress. Patients completed the Fibromyalgia Impact Questionnaire to evaluate the overall impact of fibromyalgia and controls filled out the Chronic Widespread Pain Questionnaire to detect potential cases of fibromyalgia.

RESULTS

Ninety-three percent of the total study population was female, with a mean age of 50 years. We identified 6 cases of widespread pain among controls. The average Fibromyalgia Impact Questionnaire score for patients was 67.28 +/- 14.25. All gastrointestinal symptoms except for vomiting were more frequent in patients. Ninety-eight percent of patients with fibromyalgia had at least one FGID, compared with only 39% of controls. Fibromyalgia was correlated most highly with irritable bowel syndrome. Patients presented with significantly higher scores of psychologic distress than controls, especially those with fecal incontinence.

CONCLUSIONS

There is a prevalence of FGID in patients with fibromyalgia and a wider distribution of such symptoms along the gastrointestinal tract compared with controls. We propose that an increased degree of psychologic distress in these patients predisposes them to FGID, especially significant for anorectal syndromes.

Sodium channel mutation in irritable bowel syndrome: evidence for an ion channelopathy

The SCN5A-encoded Na(v)1.5 Na(+) channel is expressed in interstitial cells of Cajal and smooth muscle in the circular layer of the human intestine. Patients with mutations in SCN5A are more likely to report gastrointestinal symptoms, especially abdominal pain. Twin and family studies of irritable bowel syndrome (IBS) suggest a genetic basis for IBS, but no genes have been identified to date. Therefore, our aims were to evaluate SCN5A as a candidate gene involved in the pathogenesis of IBS and to determine physiological consequences of identified mutations. Mutational analysis was performed on genomic DNA obtained from 49 subjects diagnosed with IBS who reported at least moderately severe abdominal pain. One patient hosted a loss-of-function missense mutation, G298S, that was not observed in >3,000 reference alleles derived from 1,500 healthy control subjects. Na(+) currents were recorded from the four common human SCN5A transcripts in transfected HEK-293 cells. Comparing Na(v)1.5 with G298S-SCN5A versus wild type in HEK cells, Na(+) current density was significantly less by 49-77%, and channel activation time was delayed in backgrounds that also contained the common H558R polymorphism. Single-channel measurements showed no change in Na(v)1.5 conductance. Mechanosensitivity was reduced in the H558/Q1077del transcript but not in the other three backgrounds. In conclusion, the G298S-SCN5A missense mutation caused a marked reduction of whole cell Na(+) current and loss of function of Na(v)1.5, suggesting SCN5A as a candidate gene in the pathophysiology of IBS.

Genetic determination of irritable bowel syndrome

Irritable bowel syndrome (IBS) is a common functional gastrointestinal disorder. According to the Rome III criteria, IBS is defined as recurrent abdominal pain or discomfort for at least 3 d per month during the previous 3 mo associated with two or more of the following symptoms: improvement with defecation, onset associated with a change in the frequency of stool and/or onset associated with a change in form or appearance of stool. There is growing evidence regarding the genetic contribution in IBS, however the precise etiology of IBS is still unknown. The evaluation of the genetic influence is based on twin studies, familial aggregation and genetic epidemiological investigations. Most studies showed a concordance for IBS significantly greater in monozygotic than in dizygotic twins. The majority of the studies have shown that familial aggregation may represent exposures to a similar environment, as well as the influence of genetic factors. Whereas no specific gene has been identified in association with IBS, recent studies have noticed the importance of polymorphisms in the promoter region of the serotonin reuptake transporter gene, G-protein beta 3 subunit gene (C825T), cholecystokinin receptor (CCKAR gene 779T>C), and high-producer tumor necrosis factor genotype. Further studies are necessary to determine how genetic factors influence the clinical manifestations and therapeutical response in IBS patients.

The genetics of the serotonin transporter and irritable bowel syndrome

Serotonin transporter (SERT) mediates the intracellular reuptake of released serotonin, thus regulating its biological functions. Abnormalities in serotonin reuptake can alter enteric serotonergic signalling, leading to sensory, motor and secretory gut dysfunctions, which contribute to the pathophysiology of irritable bowel syndrome (IBS). This relationship has fostered the use of selective serotonin reuptake inhibitors (SSRIs) in the treatment of IBS. Current data on the efficacy of SSRIs in IBS, association of the SERT gene promoter polymorphism 5-HTTLPR with IBS and the expression pattern of SERT in the intestinal mucosa of IBS patients are conflicting. Recent molecular studies have raised critical questions about multiple SERT mRNA transcripts in the human gut, the role of polymorphic SERT promoter in the regulation of enteric SERT expression and the ability of 5-HTTLPR to affect human SERT gene transcription. The present review highlights recent advances in SERT genetics, discusses their implications for potential therapeutic applications of SSRIs in IBS and presents original suggestions for future investigations.

Functional gastrointestinal disorders as a public health problem

The functional gastrointestinal disorders (FGIDs) are a heterogeneous group of chronic conditions that are considered to be important to public health because they are remarkably common, can be disabling, and induce a major social and economic burden. Despite the Rome consensus process, the line defining true abnormality from health is as yet imprecise. Furthermore, the concept that the FGIDs have no pathological or biochemical correlates is starting to unravel, and some candidate morphometric abnormalities (e.g. duodenal eosinophilia, colonic mastocytosis) have been documented. The quality of care that patients with FGIDs receive is not well understood, despite the high volume of patients seen in primary and specialty care. There are a remarkable number of symptom-based and disease-based co-morbidities that appear to be more common in those with FGIDs that are not alone explained by coexistent somatization. Whether there is any means of preventing the development of FGIDs post-infection is untested but has vast public health implications. Defining disease severity remains key to better understanding the public health impact of FGIDs; severity is probably influenced by the intestinal and extra-intestinal symptom burden, psychological distress and the impact on quality of life, but how these factors interact remains uncertain. An important future research direction must be to quantify at what risk level it is reasonable to prescribe a medication that may be dangerous, and stratify which subsets of patients with FGIDs would qualify for such an approach using objective well validated tools (e.g. based on accurately defining gradations of severity of disease). Finally, there are some reasons to suspect that there may be an increase in mortality in FGID sufferers; for example, unnecessary surgery or invasive testing has a small but not zero associated mortality, and this should be a factor in view of the high prevalence of disease.

Cognitive-affective neuroscience of somatization disorder and functional somatic syndromes: reconceptualizing the triad of depression-anxiety-somatic symptoms

Somatization disorder is a somatoform disorder that overlaps with a number of functional somatic syndromes and has high comorbidity with major depression and anxiety disorders. Proposals have been made for revising the category of somatoform disorders, for simplifying the criteria for somatization disorder, and for emphasizing the unitary nature of the functional somatic syndromes in future classifications. A review of the cognitive-affective neuroscience of somatization disorder and related conditions suggests that overlapping psychobiological mechanisms mediate depression, anxiety, and somatization symptoms. Particular genes and environments may contribute to determining whether symptoms are predominantly depressive, anxious, or somatic, and there are perhaps also overlaps and distinctions in the distal evolutionary mechanisms that produce these symptoms.

Meta-analysis: a functional polymorphism in the gene encoding for activity of the serotonin transporter protein is not associated with the irritable bowel syndrome

BACKGROUND

Serotonin is associated with symptoms of the irritable bowel syndrome, its action is terminated by the serotonin transporter protein.

AIM

To assess the association between a functional polymorphism in the gene encoding for activity of the serotonin transporter protein and the irritable bowel syndrome.

METHODS

Meta-analysis of studies identified through a Medline, PubMed and Web of Science search, describing the prevalence of a polymorphism in the serotonin transporter gene creating long and short alleles.

RESULTS

Eight eligible studies described a total of 1034 patients with the irritable bowel syndrome, and 1377 healthy controls. Presence of the short allele is not associated with an increased risk for the irritable bowel syndrome: OR 1.0; 95% CI: 0.7-1.4 for homozygous subjects, and OR 1.0; 95% CI: 0.8-1.2 for homozygous subjects and heterozygotes together. Although Caucasians and Asians had diverging genotypic frequencies, no association with the shot allele and irritable bowel syndrome was observed in subgroups: Asians OR 1.2; 95% CI: 0.9-1.6 and OR 1.1; 95% CI: 0.2-5.9; Caucasians OR 0.9; 95% CI: 0.5-1.7 and OR 0.9; 95% CI: 0.7-1.2, respectively, for homozygous subjects alone and for homozygous subjects and heterozygotes together.

CONCLUSION

A genetic polymorphism in the gene encoding for activity of the serotonin transporter protein is not associated with the irritable bowel.

A genetic association study of 5-HTT LPR and GNbeta3 C825T polymorphisms with irritable bowel syndrome

A pharmacogenetic study suggests the 5-HTT LPR polymorphism predicts response to alosetron, and another study describes a possible association of the GNbeta3 C825T polymorphism with IBS in patients with dyspepsia. We performed a case-control association study to determine whether these polymorphisms are associated with irritable bowel syndrome (IBS). The study aim was to compare allele and genotype frequencies between cases and controls for the 5-HTT LPR and the GNbeta3 C825T polymorphism. Cases were 50 GI outpatients; controls were 53 General Medicine outpatients matched to cases for age, gender and race at a major medical centre. Participants completed a questionnaire and donated blood. DNA was genotyped using polymerase chain reaction based assays. Eighty-two per cent of cases met Rome II criteria for IBS: 12% constipation-, 46% diarrhoea-, and 42% mixed-IBS. Genotype and allele frequencies for both polymorphisms did not differ between cases and controls. However, the allele frequency of the short (S) allele of the 5-HTT LPR polymorphism was greater in those with mixed-IBS compared with controls (68%vs 45%, P < 0.05). This study suggests that the 5-HTT LPR polymorphism may be associated with mixed-IBS, but not IBS overall. No association was observed for the GNbeta3 C825T polymorphism with IBS overall or subtypes.

Psychosocial factors at work and in every day life are associated with irritable bowel syndrome

The etiology of irritable bowel syndrome (IBS) tends to be complex and multi-factorial and there is still a lack of understanding of how different psychosocial factors are associated with the syndrome. Our aim was to examine the occurrence of psychosocial and behavioural factors among patients diagnosed with IBS in primary care. The study had an epidemiological population-based case-control design comparing 347 IBS cases to 1041 age and sex matched controls from the general population. A survey was directed to cases and controls based on validated questions asking for mood status, job strain, family history of IBS, and sleeping habits as well as education, nutritional and exercise habits and medication. In multivariate analyses, independent associations were found between IBS and lack of influence on work planning, a family history of IBS, anxiety, and sleeping disturbances. Important factors associated with IBS diagnosis among females were anxiety as well as family history of IBS and lack of co-determination at work. For males, only lack of influence on working pace and family history of IBS remained independently associated with an IBS diagnosis. The causal associations of the complex risk factor panorama for IBS warrants further study. This study indicates that there should be a special focus on investigating the psychosocial working conditions and their associations to IBS.

Management of functional somatic syndromes

Although functional somatic syndromes (FSS) show substantial overlap, treatment research is mostly confined to single syndromes, with a lack of valid and generally accepted diagnostic criteria across medical specialties. Here, we review management for the full variety of FSS, drawn from systematic reviews and meta-analyses since 2001, and give recommendations for a stepped care approach that differentiates between uncomplicated and complicated FSS. Non-pharmacological treatments involving active participation of patients, such as exercise and psychotherapy, seem to be more effective than those that involve passive physical measures, including injections and operations. Pharmacological agents with CNS action seem to be more consistently effective than drugs aiming at restoration of peripheral physiological dysfunction. A balance between biomedical, organ-oriented, and cognitive interpersonal approaches is most appropriate at this truly psychosomatic interface. In view of the iatrogenic component in the maintenance of FSS, doctor-centred interventions and close observation of the doctor-patient relationship are of particular importance.

New insights into the pathogenesis and pathophysiology of irritable bowel syndrome

The pathogenesis and pathophysiology of irritable bowel syndrome is complex and still incompletely known. Potential pathogenetic factors include genes, infectious events, psychological symptoms and other loosely defined environmental factors. Both alterations at the central and peripheral level are thought to contribute to the symptoms of irritable bowel syndrome, including psychosocial factors, abnormal gastrointestinal motility and secretion, and visceral hypersensitivity. Today irritable bowel syndrome is viewed upon as a disorder of dysregulation of the so-called brain-gut axis, involving abnormal function in the enteric, autonomic and/or central nervous systems, with peripheral abnormalities probably dominating in some patients and disturbed central processing of signals from the periphery in others. Lines of evidence also suggest that inflammation within the gastrointestinal tract may be of great importance in at least subgroups of irritable bowel syndrome patients. To conclude, a complex picture of the pathogenesis and pathophysiology of irritable bowel syndrome is emerging, with interactions between several different alterations resulting in the divergent symptom pattern in these patients.

Serotonergic and non-serotonergic targets in the pharmacotherapy of visceral hypersensitivity

Visceral hypersensitivity is considered a key mechanism in the pathogenesis of functional gastrointestinal (GI) disorders. Targeting visceral hypersensitivity seems an attractive approach to the development of drugs for functional GI disorders. This review summarizes current knowledge on targets for the treatment of visceral hypersensitivity, and the status of current and future drug and probiotic treatment development, and the role of pharmacogenomic factors.

Somatic referral of visceral sensations and rectal sensory threshold for pain in children with functional gastrointestinal disorders

OBJECTIVE

To test the hypothesis that abdominal pain related to functional gastrointestinal disorders is associated with visceral hypersensitivity and abnormal perception of visceral sensations.

STUDY DESIGN

We examined 35 children (10-17.6 years old) fulfilling the Rome II criteria with irritable bowel syndrome (IBS; n = 21), functional abdominal pain (FAP; n = 8) or functional dyspepsia (FD; n = 6) compared with 10 control subjects (10.2-16.1 years). All underwent a rectal barostat examination. Painful sensations were reported on a human body diagram. The projections of sensations induced by rectal distension, the rectal sensory threshold for pain (RSTP) and the diagnostic value of RSTP measurements were measured.

RESULTS

Rectal distension induced sensations that projected to the S3 dermatome in the control subjects and FD and to aberrant sites in children with IBS and FAP. The RSTP was decreased in children with IBS and FAP compared with control subjects (P <.002) and was not different in children with FD compared with control subjects. At 30.8 mm Hg, the 5th percentile for the control subjects, the RSTP had a sensitivity rate of 89% and a specificity rate of 83% for IBS and FAP diagnosis.

CONCLUSION

Children with IBS and FAP are characterized by the association of rectal hypersensitivity and abnormal pain referral after rectal distension.

Maternal serotonin is crucial for murine embryonic development

The early appearance of serotonin and its receptors during prenatal development, together with the many effects serotonin exerts during CNS morphogenesis, strongly suggest that serotonin influences the development and maturation of the mammalian brain before it becomes a neuromodulator/neurotransmitter. Sites of early serotonin biosynthesis, however, have not been detected in mouse embryos or extraembryonic structures, suggesting that the main source of serotonin could be of maternal origin. This hypothesis was tested by using knockout mice lacking the tph1 gene, which is responsible for the synthesis of peripheral serotonin. Genetic crosses were performed to compare the phenotype of pups born from homozygous and heterozygous mothers. Observations provide the first clear evidence that (i) maternal serotonin is involved in the control of morphogenesis during developmental stages that precede the appearance of serotonergic neurons and (ii) serotonin is critical for normal murine development. Most strikingly, the phenotype of tph1-/- embryos depends more on the maternal genotype than on that of the concepti. Consideration of the maternal genotype may thus help to clarify the influence of other genes in complex diseases, such as mental illness.

Irritable bowel syndrome

Conceptually, the irritable bowel syndrome (IBS) has been considered a brain-gut functional disorder, but this paradigm is under serious challenge. There is increasing evidence that organic disease of the gastrointestinal tract can be identified in subsets of patients who fulfil the Rome criteria for IBS. Evidence for subtle inflammatory bowel disease, serotonin dysregulation, bacterial overgrowth and central dysregulation continue to accumulate. The underlying causes of IBS remain to be adequately identified, but postinfectious IBS is a clear-cut entity. Furthermore, a genetic contribution to IBS also seems likely. Diagnosis continues to be based on the symptom profile and the absence of alarm features. A heightened awareness of coeliac disease masquerading as IBS is becoming accepted. Management remains largely based on symptomatic rather than on disease-modifying therapy, but this is likely to change in the near future. Here, recent advances in the pathophysiology and management of IBS are considered.