A controlled trial of gluten-free diet in patients with irritable bowel syndrome-diarrhea: effects on bowel frequency and intestinal function

Irritable bowel syndrome: an integrated explanatory model for clinical practice

BACKGROUND

Although irritable bowel syndrome (IBS) is a symptom-based diagnosis, clinicians' management of and communication about the disorder is often hampered by an unclear conceptual understanding of the nature of the problem. We aimed to elucidate an integrated explanatory model (EM) for IBS from the existing literature for pragmatic use in the clinical setting.

METHODS

Systematic and exploratory literature searches were performed in PubMed to identify publications on IBS and EMs.

KEY RESULTS

The searches did not identify a single, integrated EM for IBS. However, three main hypotheses were elucidated that could provide components with which to develop an IBS EM: (i) altered peripheral regulation of gut function (including sensory and secretory mechanisms); (ii) altered brain-gut signaling (including visceral hypersensitivity); and (iii) psychological distress. Genetic polymorphisms and epigenetic changes may, to some degree, underlie the etiology and pathophysiology of IBS and could increase the susceptibility to developing the disorder. The three model components also fit into one integrated explanation for abdominal symptoms and changes in stool habit. Additionally, IBS may share a common pathophysiological mechanism with other associated functional syndromes.

CONCLUSIONS & INFERENCES

It was possible to elucidate an integrated, three-component EM as a basis for clinicians to conceptualize the nature of IBS, with the potential to contribute to better diagnosis and management, and dialog with sufferers.

Gluten Intake Is Positively Associated with Plasma α2-Macroglobulin in Young Adults

BACKGROUND

Gluten-free foods have increased in popularity over the past decade and are now being consumed by individuals without celiac disease. However, the physiologic effects of gluten intake in individuals without celiac disease remain unknown. High-abundance plasma proteins involved in inflammation, endothelial function, and other physiologic pathways may represent potential biomarkers of biological effects of gluten intake.

OBJECTIVE

The objective was to examine the association between gluten intake and plasma proteomic biomarkers in a population of adults without clinically diagnosed celiac disease.

METHODS

Subjects (n = 1095) were participants of the Toronto Nutrigenomics and Health Study, a cross-sectional examination of young adults aged 20-29 y. Dietary gluten intake was estimated by using a 1-mo, 196-item semiquantitative food-frequency questionnaire. The concentrations of 54 plasma proteins were measured simultaneously by liquid chromatography/multiple-reaction monitoring mass spectrometry. The association between gluten intake and each proteomic biomarker was examined by using general linear models. Analyses were then conducted in individuals who do not have the human leukocyte antigen (HLA)-DQ2 or DQ8 risk variants required for the development of celiac disease to determine whether any associations observed could have been due to undiagnosed cases of celiac disease.

RESULTS

Increased gluten intake was associated with increased concentrations of plasma α2-macroglobulin (P = 0.01), a marker of inflammation and cytokine release. The association remained after adjusting for age, sex, BMI, ethnicity, physical activity, energy intake, fiber intake, and hormonal contraceptive use among women. This relation was not modified by HLA risk variants.

CONCLUSION

Gluten consumption is associated with increased plasma α2-macroglobulin in young adults, which appears to be independent of celiac disease, suggesting possible effects of gluten on inflammation.

Wheat-related disorders reviewed: making a grain of sense

Wheat-related disorders have become a growing area of clinical and scientific interest and can be categorized broadly as: autoimmune-mediated; allergic; and non-autoimmune/non-allergic conditions. Non-celiac gluten sensitivity (NCGS) and non-celiac wheat sensitivity (NCWS) present on this spectrum as disorders associated with adverse gastrointestinal and extra-intestinal manifestations following exposure to gluten and/or other wheat-related constituents. NCGS/NCWS is increasingly considered in patients with unexplained symptoms after the exclusions of celiac disease and wheat allergy. As objective diagnostic data and specific biomarkers are lacking, response to a gluten-free/wheat-free diet can confirm the presence of NCGS/NCWS. An association with irritable bowel syndrome has been detected, and the effects of other food components, such as fermentable oligosaccharides, disaccharides, monosaccharides, and polyols, may contribute. Our organization and synthesis of extant knowledge pertaining to wheat-related disorders may advance current practice and research efforts toward an improved understanding of NCGS/NCWS as an evolving clinical entity.

Non-celiac gluten sensitivity: a work-in-progress entity in the spectrum of wheat-related disorders

Non-celiac gluten sensitivity is an undefined syndrome with gastrointestinal and extra-intestinal manifestations triggered by gluten in patients without celiac disease and wheat allergy. The pathogenesis involves immune-mediated mechanisms requiring further research. Symptoms disappear in a few hours or days after gluten withdrawal and recur rapidly after gluten ingestion. Besides gluten, other wheat proteins as well as fermentable oligo-, di-, mono-saccharides and polyols (FODMAPs) may contribute to this syndrome. This syndrome occurs mainly in young women, being rare in children. Its prevalence ranges from 0.6% to 6%, based on primary or tertiary care center estimates. No biomarker is available, but half of patients tests positive for IgG anti-gliadin antibodies, which disappear quickly after gluten-free diet together with symptoms. Also, genetic markers are still undefined. Although currently limited to a research setting, double-blind, placebo-controlled, cross-over trial strategy is recommended to confirm the diagnosis. Treatment is based on dietary restriction with special care to nutrient intake.

A systematic review of adherence to restricted diets in people with functional bowel disorders

Functional bowel disorders such as irritable bowel syndrome are commonly experienced within the population, and have an adverse impact on emotions, physical well-being, social activity, and occupational output. Adherence to a restricted diet can reduce symptoms, which in turn leads to increased quality of life and well-being. The aim of this review was to assess the extent to which predictors of dietary adherence have been considered in studies relating to functional bowel disorders and following a restricted diet. This was done firstly by examining such studies which contained a measure or indicator of adherence, and then by examining predictors of adherence within and between studies. A search of PsycINFO, Medline, CINAHL, Web of Science, and Cochrane databases was performed during July 2014, with the search criteria including relevant terms such as gastrointestinal disorder, irritable bowel syndrome, diet, and adherence. Of an initial 7927 papers, 39 were suitable for inclusion. Fourteen of the 39 studies included had a structured measure or indicator of dietary adherence, and the remaining 25 mentioned adherence without any structured levels of adherence. There was little investigation into the predictors of adherence, with symptom relief or induction being the primary goal of most of the studies. This review indicates that predictors of dietary adherence are rarely considered in research regarding functional bowel disorders. Further investigation is needed into the variables which contribute to rates of adherence to restricted diets, and more rigorous research is needed to characterise those individuals most likely to be non-adherent. Such research is necessary to ensure that people with these conditions can be provided with appropriate support and interventions.

Systematic review: noncoeliac gluten sensitivity

BACKGROUND

Noncoeliac gluten sensitivity (NCGS) is a controversial emerging disorder. Despite reported symptoms related to the ingestion of gluten, NCGS remains a diagnosis based on the exclusion of coeliac disease, given the absence of reliable biomarkers.

AIM

To evaluate the prevalence, diagnostic exclusion of coeliac disease and the efficacy of a gluten-free diet (GFD) for NCGS patients.

METHODS

A PubMed search was performed up to December 2014. According to consensus diagnostic criteria, NCGS was defined as self-reported gluten intolerance, negative coeliac serology and absence of villous atrophy. Studies evaluating the impact of a GFD on patients with irritable bowel syndrome (IBS) were also included.

RESULTS

Prevalence rates of NCGS (0.5-13%) differed widely. Seventeen studies, including 1561 patients (26 children), met the inclusion criteria for NCGS. HLA haplotypes could not be linked to histology [normal or lymphocytic enteritis (LE)] in 1123 NCGS patients. HLADQ2/DQ8 haplotypes were present in 44% of NCGS patients. After advanced diagnostic techniques in 189 NCGS patients combining LE and HLADQ2/DQ8 haplotypes, 39 (20%) were reclassified as coeliac disease. There was a higher than expected family history of coeliac disease and autoimmune disorders in NCGS patients. A GFD resulted in variable results for variable, but significantly improved stool frequency in HLADQ2 positive diarrhoea-predominant IBS patients.

CONCLUSIONS

Prevalence rates for NCGS are extremely variable. A subset of NCGS patients might belong in the so-called 'coeliac-lite' disease. The benefit of a GFD for NCGS patients is currently controversial. HLADQ2 positive diarrhoea-type IBS patients might gain symptom improvement from a GFD.

Food components and irritable bowel syndrome

Ingestion of food has long been linked with gut symptoms, and there is increasing interest in using diet in the management of patients with irritable bowel syndrome (IBS). The West has developed an intense interest in specialized, restrictive diets, such as those that target multiple food groups, avoid gluten, or reduce fermentable oligo-, di-, and mono-saccharides and polyols. However, most gastroenterologists are not well educated about diets or their effects on the gut. It is important to understand the various dietary approaches, their putative mechanisms, the evidence that supports their use, and the benefits or harm they might produce. The concepts behind, and delivery of, specialized diets differ from those of pharmacologic agents. High-quality research is needed to determine the efficacy of different dietary approaches and the place of specific strategies.

Nonceliac gluten sensitivity

During the past decade there has been an impressive increase in popularity of the gluten-free diet (GFD)-now the most trendy alimentary habit in the United States and other countries. According to recent surveys, as many as 100 million Americans will consume gluten-free products within a year. Operating under the concept that the GFD benefits only individuals with celiac disease, health care professionals have struggled to separate the wheat from the chaff; there are claims that eliminating gluten from the diet increases health and helps with weight loss, or even that gluten can be harmful to every human being. However, apart from unfounded trends, a disorder related to ingestion of gluten or gluten-containing cereals, namely nonceliac gluten sensitivity (NCGS), has resurfaced in the literature, fueling a debate on the appropriateness of the GFD for people without celiac disease. Although there is clearly a fad component to the popularity of the GFD, there is also undisputable and increasing evidence for NCGS. However, we require a better understanding of the clinical presentation of NCGS, as well as its pathogenesis, epidemiology, management, and role in conditions such as irritable bowel syndrome, chronic fatigue, and autoimmunity. Before we can begin to identify and manage NCGS, there must be agreement on the nomenclature and definition of the disorder based on proper peer-reviewed scientific information. We review the most recent findings on NCGS and outline directions to dissipate some of the confusion related to this disorder.

Non-coeliac gluten sensitivity: piecing the puzzle together

The avoidance of wheat- and gluten-containing products is a worldwide phenomenon. While coeliac disease is well-established, much remains unknown about whether gluten can be a trigger of gastrointestinal and/or extra-intestinal symptoms in patients without coeliac disease. In this article, we discuss the latest scientific evidence and our current understanding for the possible mechanisms of this largely ambiguous group, termed 'non-coeliac gluten sensitive' (NCGS). We can conclude that NCGS should be regarded as an independent disease outside of coeliac disease and wheat allergy, and that the number of patients affected is likely to be limited. Many questions remain unanswered and it needs to be verified whether the elimination of dietary gluten alone is sufficient for the control of symptoms, and to understand the overlap with other components of wheat.

Other Dietary Confounders: FODMAPS et al

BACKGROUND

While it is well documented and widely appreciated that ingestion of wheat (and less so rye and barley) is associated with gastrointestinal symptoms such as bloating or abdominal pain, the component of wheat to which such an effect is attributed is less well established.

KEY MESSAGES

Wheat is a complex of proteins (80% gluten, 20% metabolic proteins), carbohydrates (starch, non-starch polysaccharides, fructans), lipids and other components. The majority of attention has focused on gluten as the culprit in triggering symptoms, but re-challenge studies have nearly all used wheat flour-related products (such as bread) as the stimulus. When carbohydrate-deplete gluten was used as the challenge agent, gluten-specific feelings of depression and not gut symptoms were observed in those who fulfilled strict criteria of 'non-coeliac gluten sensitivity', thereby underlining the complexity of cereals and of undertaking research in this area. Candidate components other than gluten include poorly absorbed oligosaccharides (mainly fructans), non-gluten wheat proteins such as amylase-trypsin inhibitors or wheat germ agglutinin, and exorphins released during the digestion of gluten. Specific biological and/or clinical effects associated with gluten-free diets or wheat ingestion need to be carefully dissected before attribution to gluten can be claimed.

CONCLUSIONS

Currently, coeliac disease is the only common condition that has been unequivocally linked to gluten. Inaccurate attribution will be associated with suboptimal therapeutic advice and at least partly underlies the current gluten-free epidemic gripping the Western world.

Motility alterations in celiac disease and non-celiac gluten sensitivity

Regulation of gut motility is complex and involves neuromuscular, immune and environmental mechanisms. It is well established that patients with celiac disease (CD) often display gut dysmotility. Studies have shown the presence of disturbed esophageal motility, altered gastric emptying, and dysmotility of the small intestine, gallbladder and colon in untreated CD. Most of these motor abnormalities resolve after a strict gluten-free diet, suggesting that mechanisms related to the inflammatory condition and disease process are responsible for the motor dysfunction. Motility abnormalities are also a hallmark of functional bowel disorders such as irritable bowel syndrome (IBS), where it has been proposed as underlying mechanism for symptom generation (diarrhea, constipation, bloating). Non-celiac gluten sensitivity (NCGS) is a poorly defined entity, mostly self-diagnosed, that presents clinically with IBS symptoms in the absence of specific celiac markers. Patients with NCGS are believed to react symptomatically to wheat components, and some studies have proposed the presence of low-grade inflammation in these patients. There is little information regarding the functional characterization of these patients before and after a gluten-free diet. A study suggested the presence of altered gastrointestinal transit in NCGS patients who also have a high prevalence of nonspecific anti-gliadin antibodies. Results of an ongoing clinical study in NCGS patients with positive anti-gliadin antibodies before and after a gluten-free diet will be discussed. Elucidating the mechanisms for symptom generation in NCGS patients is important to find new therapeutic alternatives to the burden of imposing a strict gluten-free diet in patients who do not have CD.

Diet in irritable bowel syndrome

Irritable bowel syndrome (IBS) is a common chronic gastrointestinal disorder that is characterized by intermittent abdominal pain/discomfort, altered bowel habits and abdominal bloating/distension. This review aimed at presenting the recent developments concerning the role of diet in the pathophysiology and management of IBS. There is no convincing evidence that IBS patients suffer from food allergy/intolerance, and there is no evidence that gluten causes the debated new diagnosis of non-coeliac gluten sensitivity (NCGS). The component in wheat that triggers symptoms in NCGS appears to be the carbohydrates. Patients with NCGS appear to be IBS patients who are self-diagnosed and self-treated with a gluten-free diet. IBS symptoms are triggered by the consumption of the poorly absorbed fermentable oligo-, di-, monosaccharides and polyols (FODMAPs) and insoluble fibre. On reaching the distal small intestine and colon, FODMAPS and insoluble fibre increase the osmotic pressure in the large-intestine lumen and provide a substrate for bacterial fermentation, with consequent gas production, abdominal distension and abdominal pain or discomfort. Poor FODMAPS and insoluble fibres diet reduces the symptom and improve the quality of life in IBS patients. Moreover, it changes favourably the intestinal microbiota and restores the abnormalities in the gastrointestinal endocrine cells. Five gastrointestinal endocrine cell types that produce hormones regulating appetite and food intake are abnormal in IBS patients. Based on these hormonal abnormalities, one would expect that IBS patients to have increased food intake and body weight gain. However, the link between obesity and IBS is not fully studied. Individual dietary guidance for intake of poor FODMAPs and insoluble fibres diet in combination with probiotics intake and regular exercise is to be recommended for IBS patients.

Coeliac disease and noncoeliac gluten sensitivity

The spectrum of gluten-related disorders was restricted to coeliac disease and wheat allergy, but the new contemporary entity referred to as noncoeliac gluten sensitivity has gained recognition mainly in adults but also in children. Noncoeliac gluten sensitivity is defined as the presence of a variety of symptoms related to gluten ingestion in patients in whom coeliac disease and wheat allergy have been excluded. The pathophysiology and biomarkers of coeliac disease and wheat allergy are well known, but this is not the case for noncoeliac gluten sensitivity. It is also not clear whether noncoeliac gluten sensitivity is caused by consumption of gluten or by consumption of fermentable oligosaccharides, disaccharides, monosaccharides, and polyols. Randomized trials on noncoeliac gluten sensitivity in children are lacking and are hardly needed to evaluate its role in paediatric patients with gastroenterology to avoid the use of unnecessary restrictive diets in children and interference with proper diagnosis of coeliac disease.

New and Emerging Treatment Options for Irritable Bowel Syndrome

Irritable bowel syndrome (IBS) is a functional gastrointestinal disorder associated with abdominal pain, diarrhea, constipation, or a mix of symptoms. The pathophysiology of IBS is not completely understood but appears to involve genetics, the gut microbiome, immune activation, altered intestinal permeability, and brain-gut interactions. There is no gold standard for diagnosis. Several sets of symptom-based guidelines exist. Treatment strategies for IBS may include both nonpharmacologic and pharmacologic approaches. Lifestyle modifications that aim to improve exercise, sleep, diet, and stress may be warranted. Recent data suggest that a gluten-free diet and a diet low in fermentable oligosaccharides, disaccharides, monosaccharides, and polyols (FODMAPs) may benefit some patients. For patients with diarrhea-predominant IBS, treatment options include the synthetic peripheral μ-opioid receptor agonist loperamide, antispasmodic agents, antidepressants, serotonin 5-HT3 antagonists, and the gut-specific antibiotic rifaximin. Ongoing research is evaluating the use of probiotics. For patients with constipation-predominant IBS, therapeutic strategies may include dietary fiber, laxatives, and the prosecretory agents lubiprostone and linaclotide. Research is continuing to optimize the use of available agents and evaluating new approaches to further improve the care of patients with IBS.

Diet and irritable bowel syndrome

PURPOSE

of review Those who suffer from irritable bowel syndrome (IBS) have long reported the frequent precipitation of their symptoms in relation to food ingestion and have often been convinced that certain foods were especially problematic. However, until very recently, research on the responses to food or individual dietary constituents, in IBS, has been scarce. This review addresses recent literature on diet and IBS.

RECENT FINDINGS

The complexity of food-symptom interactions in IBS is being revealed in recent and ongoing research. Such studies have revealed the variable effects of fibre in IBS and the susceptibility of IBS individuals to the ingestion of poorly digested and absorbed carbohydrates. The latter has led to the widespread adoption of the low-fermentable oligosaccharides, disaccharides, monosaccharides and polyols (FODMAPs) diet. Less certain is the role of another widely adopted dietary strategy, gluten restriction. Diet-microbe interactions are critical to the homeostasis of the gut microbiome in health and may well be disturbed in disease; enthusiasm continues, therefore, for the use of probiotics in IBS.

SUMMARY

Food is a common precipitant of symptoms in IBS and recent research has focused on the role(s) of individual dietary constituents in IBS and on fibre, FODMAPs, gluten and probiotics, in particular. Each may have a role in certain IBS sufferers.

Dietary treatment of irritable bowel syndrome

INTRODUCTION

Food is a recognized trigger for most patients with irritable bowel syndrome (IBS). In recent years, an emerging evidence base has identified dietary manipulation as an important therapeutic approach in IBS.

SOURCES OF DATA

Original and review articles were identified through selective searches performed on PubMed and Google Scholar.

AREAS OF AGREEMENT

Randomized controlled trials have supported the use of a diet that restricts a group of short-chain carbohydrates known collectively as fermentable oligosaccharides, disaccharides, monosaccharides and polyols (FODMAPs). There is evidence that specific probiotics may improve symptoms in IBS.

AREAS OF CONTROVERSY

The role of a high-fibre diet remains subject to ongoing debate with a lack of high-quality evidence. The long-term durability and safety of a low FODMAP diet are unclear.

GROWING POINTS

A paradigm shift has led to a focus on the relationship between diet and pathophysiological mechanisms in IBS such as effects on intestinal microbiota, inflammation, motility, permeability and visceral hypersensitivity.

AREAS TIMELY FOR DEVELOPING RESEARCH

Future large, randomized controlled trials with rigorous end points are required. In addition, predictors of response need to be identified to offer personalized therapy.

Effect of gliadin on permeability of intestinal biopsy explants from celiac disease patients and patients with non-celiac gluten sensitivity

Background: Intestinal exposure to gliadin leads to zonulin upregulation and consequent disassembly of intercellular tight junctions and increased intestinal permeability. We aimed to study response to gliadin exposure, in terms of barrier function and cytokine secretion, using intestinal biopsies obtained from four groups: celiac patients with active disease (ACD), celiac patients in remission (RCD), non-celiac patients with gluten sensitivity (GS) and non-celiac controls (NC). Methods: Ex-vivo human duodenal biopsies were mounted in microsnapwells and luminally incubated with either gliadin or media alone. Changes in transepithelial electrical resistance were monitored over 120 min. Media was subsequently collected and cytokines quantified. Results: Intestinal explants from all groups (ACD (n = 6), RCD (n = 6), GS (n = 6), and NC (n = 5)) demonstrated a greater increase in permeability when exposed to gliadin vs. media alone. The increase in permeability in the ACD group was greater than in the RCD and NC groups. There was a greater increase in permeability in the GS group compared to the RCD group. There was no difference in permeability between the ACD and GS groups, between the RCD and NC groups, or between the NC and GS groups. IL-10 was significantly greater in the media of the NC group compared to the RCD and GS groups. Conclusions: Increased intestinal permeability after gliadin exposure occurs in all individuals. Following gliadin exposure, both patients with gluten sensitivity and those with active celiac disease demonstrate a greater increase in intestinal permeability than celiacs in disease remission. A higher concentration of IL-10 was measured in the media exposed to control explants compared to celiac disease in remission or gluten sensitivity.

A Grounded Guide to Gluten: How Modern Genotypes and Processing Impact Wheat Sensitivity

The role of wheat, and particularly of gluten protein, in our diet has recently been scrutinized. This article provides a summary of the main pathologies related to wheat in the human body, including celiac disease, wheat allergy, nonceliac wheat sensitivity, fructose malabsorption, and irritable bowel syndrome. Differences in reactivity are discussed for ancient, heritage, and modern wheats. Due to large variability among species and genotypes, it might be feasible to select wheat varieties with lower amounts and fewer types of reactive prolamins and fructans. Einkorn is promising for producing fewer immunotoxic effects in a number of celiac research studies. Additionally, the impact of wheat processing methods on wheat sensitivity is reviewed. Research indicates that germination and fermentation technologies can effectively alter certain immunoreactive components. For individuals with wheat sensitivity, less-reactive wheat products can slow down disease development and improve quality of life. While research has not proven causation in the increase in wheat sensitivity over the last decades, modern wheat processing may have increased exposure to immunoreactive compounds. More research is necessary to understand the influence of modern wheat cultivars on epidemiological change.

The rise and fall of gluten!

Mankind has existed for 2·5 million years but only in the last 10 000 years have we been exposed to wheat. Wheat was first cultivated in the Fertile Crescent (South Western Asia) with a farming expansion that lasted from about 9000BC to 4000BC. Thus it could be considered that wheat (and gluten) is a novel introduction to man's diet! Prior to 1939 the rationing system had already been devised. This led to an imperative to try to increase agricultural production. Thus it was agreed in 1941 that there was a need to establish a Nutrition Society. The very roots of the society were geared towards necessarily increasing the production of wheat. This goal was achieved and by the end of the 20th century, global wheat output had expanded 5-fold. Perhaps as a result the epidemiology of coeliac disease (CD) or gluten sensitive enteropathy has changed. CD is a state of heightened immunological responsiveness to ingested gluten in genetically susceptible individuals. CD now affects 1 % or more of all adults, for which the treatment is a strict lifelong gluten-free diet. However, there is a growing body of evidence to show that a far greater proportion of individuals without coeliac disease are taking a gluten-free diet of their own volition. This clinical entity has been termed non-coeliac gluten sensitivity (NCGS), although the condition is fraught with complexities due to overlap with other gluten-based constituents that can also trigger similar clinical symptoms. This review will explore the relationship between gluten, the rising prevalence of modern coeliac disease, and the new entity of NCGS along with its associated uncertainties.

Metabolic syndrome in patients with coeliac disease on a gluten-free diet

BACKGROUND

Several studies have shown that weight changes are common in patients with coeliac disease after starting a gluten-free diet (GFD), but data on the prevalence of metabolic syndrome in this population are still scarce.

AIMS

To assess the prevalence of metabolic syndrome in patients with CD at diagnosis and 1 year after starting GFD.

METHODS

We enrolled all consecutive patients with newly diagnosed coeliac disease (CD) who were referred to our third-level CD Unit. For all patients we collected: waist circumference, BMI, blood pressure, lipid profile (HDL cholesterol, triglycerides) and levels of blood glucose. Diagnosis of metabolic syndrome was made according to the International Diabetes Federation (IDF) criteria for European countries. The prevalence of metabolic syndrome was re-assessed after 12 months of GFD.

RESULTS

Ninety-eight patients with CD were assessed, two patients with CD (2%) fulfilled the diagnostic criteria for metabolic syndrome at diagnosis and 29 patients (29.5%) after 12 months of GFD (P < 0.01; OR: 20). With regard to metabolic syndrome sub-categories 1 year after GFD compared to baseline respectively: 72 vs. 48 patients exceeded waist circumference cut-off (P < 0.01; OR: 2.8); 18 vs. 4 patients had high blood pressure (P < 0.01; OR: 5.2); 25 vs. 7 patients exceeded glycemic threshold (P = 0.01; OR: 4.4); 34 vs. 32 patients with CD had reduced levels of HDL cholesterol (P = 0.7); and 16 vs. 7 patients had high levels of triglycerides (P = 0.05).

CONCLUSIONS

Patients with coeliac disease show a high risk of metabolic syndrome 1 year after starting a gluten-free diet. We suggest that an in-depth nutritional assessment is undertaken for all patients with coeliac disease.

The quest for biomarkers in IBS-where should it lead us?

Irritable bowel syndrome (IBS) is a prevalent functional gastrointestinal disorder which represents a major cost to health-care services. The diagnosis of IBS is currently performed by means of symptom-based diagnostic criteria, but there has been an ongoing interest in developing biomarkers which could simplify the diagnosis and/or evaluating the effect of treatments. This article reviews the current literature concerning the proposed biomarkers including those of altered gut motility, of visceral hypersensitivity, of abnormal brain mechanisms, of serum, fecal and mucosal inflammation and of increased intestinal permeability.

Validating biomarkers of treatable mechanisms in irritable bowel syndrome

BACKGROUND

A valid biomarker is 'an indicator of normal biologic or pathogenic processes, or pharmacological responses to a therapeutic intervention'. There is no validated biomarker for irritable bowel syndrome (IBS). The aim of the study was to assess ability of three quantitative traits to identify treatable processes to discriminate between IBS-diarrhea (IBS-D) patients, IBS-constipation (IBS-C) patients and healthy volunteers (HV).

METHODS

In 30 HV, 30 IBS-C patients and 64 IBS-D patients, we characterized bowel symptoms and quantitated pathophysiological mechanisms: bile acid (BA) synthesis (serum C4 and FGF19), fecal BA and fat, colonic transit (CT), and intestinal permeability (IP). We used multiple logistic regression and receiver-operating characteristic (ROCAUC ) to appraise three factors (fecal BA, CT, and IP) individually and in combination to identify discriminant targets for treatment in IBS.

KEY RESULTS

There were significant associations between the three subgroups and symptoms reflecting bowel function and the quantitative traits. There were significant associations between fecal BA and CT at 48 h (r = 0.43; p < 0.001) and between fecal BA and IP (r = 0.23; p = 0.015). Individually, fecal BA and CT48 (but not IP) were significant independent predictors for distinguishing HV from IBS. In combination, they discriminated HV from IBS-D patients (ROCAUC 0.70), HV from IBS-C patients (ROCAUC 0.73), and IBS-C patients from IBS-D patients (ROCAUC 0.86). Colonic transit and fecal BA excretion together discriminate between healthy volunteers and IBS-C patients or IBS-D patients, or between the IBS subgroups with 75-90% specificity at 60% sensitivity.

CONCLUSIONS & INFERENCES

Colonic transit and fecal BA individually and together constitute useful biomarkers to identify treatable mechanisms in IBS and to differentiate subgroups of IBS.

Ehealth: Low FODMAP diet vs Lactobacillus rhamnosus GG in irritable bowel syndrome

AIM: To investigate the effects of a low fermentable, oligosaccharides, disaccharides, monosaccharides and polyols diet (LFD) and the probiotic Lactobacillus rhamnosus GG (LGG) in irritable bowel syndrome (IBS).

METHODS: Randomised, unblinded controlled trial on the effect of 6-wk treatment with LFD, LGG or a normal Danish/Western diet (ND) in patients with IBS fulfilling Rome III diagnostic criteria, recruited between November 2009 and April 2013. Patients were required to complete on a weekly basis the IBS severity score system (IBS-SSS) and IBS quality of life (IBS-QOL) questionnaires in a specially developed IBS web self-monitoring application. We investigated whether LFD or LGG could reduce IBS-SSS and improve QOL in IBS patients.

RESULTS: One hundred twenty-three patients (median age 37 years, range: 18-74 years), 90 (73%) females were randomised: 42 to LFD, 41 to LGG and 40 to ND. A significant reduction in mean ± SD of IBS-SSS from baseline to week 6 between LFD vs LGG vs ND was revealed: 133 ± 122 vs 68 ± 107, 133 ± 122 vs 34 ± 95, P < 0.01. Adjusted changes of IBS-SSS for baseline covariates showed statistically significant reduction of IBS-SSS in LFD group compared to ND (IBS-SSS score 75; 95%CI: 24-126, P < 0.01), but not in LGG compared to ND (IBS-SSS score 32; 95%CI: 18-80, P = 0.20). IBS-QOL was not altered significantly in any of the three groups: mean ± SD in LFD 8 ± 18 vs LGG 7 ± 17, LFD 8 ± 18 vs ND 0.1 ± 15, P = 0.13.

CONCLUSION: Both LFD and LGG are efficatious in patients with IBS.

Confocal endomicroscopy shows food-associated changes in the intestinal mucosa of patients with irritable bowel syndrome

BACKGROUND & AIMS

We investigated suspected food intolerances in patients with irritable bowel syndrome (IBS) using confocal laser endomicroscopy (CLE) for real-time visualization of structural/functional changes in the intestinal mucosa after food challenge. Patients with functional changes after food challenge (CLE+) were placed on personalized exclusion diets and followed up for long-term symptom relief.

METHODS

Thirty-six IBS patients with suspected food intolerance and 10 patients with Barrett's esophagus (controls) without IBS symptoms were examined by CLE at University Hospital Schleswig-Holstein (Kiel, Germany). Diluted food antigens were administered directly to the duodenal mucosa through the working channel of the endoscope. Epithelial breaks, intervillous spaces, and the number of intraepithelial lymphocytes (IEL) were measured before and after the food challenge. CLE+ patients were placed on exclusion diets, given symptom score questionnaires, and followed up for 1 year; controls resumed their previous diet.

RESULTS

CLE showed a real-time response to food antigens in 22 of 36 patients; no responses were observed in 14 of 36 patients (CLE-) or any of the controls. Baseline IELs were significantly higher in CLE+ than CLE- subjects (P = .004); numbers increased significantly after food challenge (P = .0008). Within 5 minutes of exposure of CLE+ patients to food antigens, IELs increased, epithelial leaks/gaps formed, and intervillous spaces widened. Epithelial leaks and intervillous spaces also increased significantly in CLE+ vs baseline (both P < .001). The concordance of IELs measured by CLE and conventional histology was 70.6%; they did not correlate (P = .89; r(2) = 0.027). Symptom scores improved more than 50% in CLE+ patients after a 4-week exclusion diet and increased to 74% at 12 months; symptoms continued in CLE- patients.

CONCLUSIONS

Based on CLE analysis of IBS patients with a suspected food intolerance, exposure to candidate food antigens caused immediate breaks, increased intervillous spaces, and increased IELs in the intestinal mucosa. These changes are associated with patient responses to exclusion diets. Registered at clinicaltrials.gov (registration number: NCT01692613).

From intestinal permeability to dysmotility: the biobreeding rat as a model for functional gastrointestinal disorders

Background

Impaired intestinal barrier function, low-grade inflammation and altered neuronal control are reported in functional gastrointestinal disorders. However, the sequence of and causal relation between these events is unclear, necessitating a spontaneous animal model. The aim of this study was to describe the natural history of intestinal permeability, mucosal and neuromuscular inflammation and nitrergic motor neuron function during the lifetime of the BioBreeding (BB) rat.

Methods

Normoglycemic BB-diabetes prone (DP) and control rats were sacrificed at different ages and jejunum was harvested to characterize intestinal permeability, inflammation and neuromuscular function.

Results

Both structural and functional evidence of increased intestinal permeability was found in young BB-DP rats from the age of 50 days. In older animals, starting in the mucosa from 70 days and in half of the animals also in the muscularis propria from 110 days, an inflammatory reaction, characterized by an influx of polymorphonuclear cells and higher myeloperoxidase activity, was observed. Finally, in animals older than 110 days, coinciding with a myenteric ganglionitis, a loss of nitrergic neurons and motor function was demonstrated.

Conclusion

In the BB-rat, mucosal inflammatory cell infiltration is preceded by intestinal barrier dysfunction and followed by myenteric ganglionitis and loss of nitrergic function. This sequence supports a primary role for impaired barrier function and provides an insightful model for the pathogenesis of functional gastrointestinal disorders.

Dietary Renaissance in IBS: Has Food Replaced Medications as a Primary Treatment Strategy?

OPINION STATEMENT

The medical community has only recently started to focus attention on the role of food in the pathogenesis of irritable bowel syndrome (IBS), though the association between food and gastrointestinal (GI) symptoms has been recognized by patients for decades. Health care providers receive little formal training in the dietary management of IBS and have traditionally viewed dietary interventions with skepticism. There is mounting evidence that links food to changes in motility, visceral sensation, microbiome, permeability, immune activation, and brain-gut interactions-all key elements in the pathogenesis of IBS. The role of specific dietary modification in the management of IBS has not been rigorously investigated until recently. There is now credible evidence suggesting that targeted dietary carbohydrate exclusion provides clinical benefits to IBS patients. There is emerging evidence to suggest that proteins such as gluten, as well as food chemicals, may play a role in IBS.

Fermentable oligosaccharides, disaccharides, monosaccharides and polyols: role in irritable bowel syndrome

Irritable bowel syndrome (IBS) was previously left poorly treated despite its high prevalence and cost. Over the past decade, significant research has been conducted providing new dietary strategies for IBS management. The 'low fermentable oligosaccharides, disaccharides, monosaccharides and polyols diet' has shown symptom improvement in 68-76% of patients. Randomized, controlled trials have now proven its efficacy. The diet, low in poorly absorbed and fermentable carbohydrates, uses dietary restriction and re-challenge to determine individual tolerance to various short-chain carbohydrates. However there may be potential detrimental effects of the diet in the long term, due to potential changes to the gastrointestinal microbiota. Appropriate dietary education and management of the diet is imperative. Future research should focus on the relevance of changes to the microbiota and ways to liberalize the dietary restrictions.

Non coeliac gluten sensitivity - A new disease with gluten intolerance

Until recently gluten intolerance has been believed to be typical of celiac disease (CD) and wheat allergy (WA). In the last few years, however, several study results have been published that have proved that gluten intolerance can also affect people who do not suffer from any of the above mentioned diseases. The new syndrome has been named non-celiac gluten sensitivity (NCGS) or gluten sensitivity (GS). It has been included in the new list of gluten-related disorders published in 2012. Researchers believe that NCGS is the most common syndrome of gluten intolerance. This review discusses many aspects of NCGS epidemiology, pathophysiology, clinical spectrum, and treatment and current tools to identify patients suffering from CD, WA, and NCGS.

Irritable bowel syndrome: contemporary nutrition management strategies

Irritable bowel syndrome is a complex disorder whose pathophysiology involves alterations in the enteric microbiota, visceral hypersensitivity, gut immune/barrier function, hypothalamic-pituitary-adrenal axis regulation, neurotransmitters, stress response, psychological factors, and more. The importance of diet in the management of irritable bowel syndrome has taken center stage in recent times as the literature validates the relationship of certain foods with the provocation of symptoms. Likewise, a number of elimination dietary programs have been successful in alleviating irritable bowel syndrome symptoms. Knowledge of the dietary management strategies for irritable bowel syndrome will help guide nutritionists and healthcare practitioners to deliver optimal outcomes. This tutorial reviews the nutrition management strategies for irritable bowel syndrome.

Prevalence of a gluten-free diet and improvement of clinical symptoms in patients with inflammatory bowel diseases

BACKGROUND

Maintaining a gluten-free diet (GFD) without an underlying diagnosis of celiac disease has enjoyed widespread acceptance in the Unites States.

METHODS

We performed a cross-sectional study using a GFD questionnaire in 1647 patients with inflammatory bowel diseases (IBD) participating in the CCFA Partners longitudinal Internet-based cohort.

RESULTS

A diagnosis of celiac disease and non-celiac gluten sensitivity were reported by 10 (0.6%) and 81 (4.9%) respondents, respectively. Three hundred fourteen (19.1%) participants reported having previously tried a GFD and 135 (8.2%) reported current use of GFD. Overall 65.6% of all patients, who attempted a GFD, described an improvement of their gastrointestinal symptoms and 38.3% reported fewer or less severe IBD flares. In patients currently attempting a GFD, excellent adherence was associated with significant improvement of fatigue (P < 0.03).

CONCLUSIONS

In this large group of patients with IBD, a substantial number had attempted a GFD, of whom the majority had some form of improvement in gastrointestinal symptoms. Testing a GFD in clinical practice in patients with significant intestinal symptoms, which are not solely explained by the degree of intestinal inflammation, has the potential to be a safe and highly efficient therapeutic approach. Further prospective studies into mechanisms of gluten sensitivity in IBD are warranted.

RNA sequencing shows transcriptomic changes in rectosigmoid mucosa in patients with irritable bowel syndrome-diarrhea: a pilot case-control study

Our aim was to conduct a pilot case-control study of RNA expression profile using RNA sequencing of rectosigmoid mucosa of nine females with -diarrhea-predominant irritable bowel syndrome (IBS-D) with accelerated colonic transit and nine female healthy controls. Mucosal total RNA was isolated and purified, and next-generation pair-end sequencing was performed using Illumina TruSeq. Analysis was carried out using a targeted approach toward 12 genes previously associated with IBS and a hypothesis-generating approach. Of the 12 targeted genes tested, patients with IBS-D had decreased mRNA expression of TNFSF15 (fold change controls to IBS-D: 1.53, P = 0.01). Overall, up- and downregulated mRNA expressions of 21 genes (P = 10(-5) to 10(-8); P values with false detection rates are shown) were potentially relevant to IBS-D including the following: neurotransmitters [P2RY4 (P = 0.001), vasoactive intestinal peptide (VIP, P = 0.02)]; cytokines [CCL20 (P = 0.019)]; immune function [C4BPA complement cascade (P = 0.0187)]; interferon-related [IFIT3 (P = 0.016)]; mucosal repair and cell adhesion [trefoil protein (TFF1, P = 0.012)], retinol binding protein [RBP2 (P = 0.017)]; fibronectin (FN1, P = 0.009); and ion channel functions [guanylate cyclase (GUCA2B, P = 0.017), PDZ domain-containing protein 3 (PDZD3, P = 0.029)]. Ten genes associated with functions related to pathobiology of IBS-D were validated by RT-PCR. There was significant correlation in fold changes of the selected genes (Rs = 0.73, P = 0.013). Up- or downregulation of P2RY4, GUC2AB, RBP2, FNI, and C4BPA genes were confirmed on RT-PCR, which also revealed upregulation of farnesoid X receptor (FXR) and apical sodium-coupled bile acid transporter (IBAT/ASBT). RNA-Seq and RT-PCR analysis of rectosigmoid mucosa in IBS-D show transcriptome changes that provide the rationale for validation studies to explore the role of mucosal factors in the pathobiology of IBS-D.

Functional bowel symptoms and diet

It is well recognised that ingestion of food is a trigger for functional bowel symptoms, particularly those associated with irritable bowel syndrome (IBS). Patients often use manipulation of diet as a means of controlling symptoms. Despite description of multiple dietary methods, few have scientific backing or quality evidence of efficacy. One approach is to define how specific food components influence the pathophysiology of IBS and then rationally design dietary approaches. For example, short-chain poorly absorbed carbohydrates (fermentable oligo-, di- and mono-saccharides and polyols (FODMAP)) cause luminal distension, which is a major stimulus for the development of symptoms in patients with visceral hypersensitivity. By determining food content of FODMAP, a diet in which foods low in FODMAP are favoured over those high in FODMAP can be designed. Observational, comparative and randomised controlled treatment and rechallenge studies have shown that such an approach is efficacious in the majority of patients with IBS. The low FODMAP diet is now the primary dietary therapy for such patients. Similar approaches can be applied to other food components, including proteins (such as gluten), fats and natural bioactive food chemicals. Such approaches have suggestions of efficacy, but the evidence base remains underdeveloped. An additional and important consideration for any dietary therapy is its nutritional adequacy and potential adverse health effects. Dietary manipulation is now a key management strategy in patients with functional bowel symptoms. Future well-designed interventional studies will lead to refinement of dietary approaches taken and to a better understanding of their long-term safety.

Characteristics of patients who avoid wheat and/or gluten in the absence of Celiac disease

BACKGROUND

Gastrointestinal symptoms that respond to the removal of wheat and/or gluten are becoming more common. Patients who avoid wheat and/or gluten (PWAWG) are a heterogeneous group and predominantly self-diagnosed prior to presenting for clinical evaluation.

SPECIFIC AIM

We characterized PWAWGs seen at a tertiary care referral center and compared them to patients with celiac disease (CD) and subjects in the National Health and Nutrition examination survey (NHANES).

METHODS

This was a cross-sectional study evaluating patients seen by four gastroenterologists at a CD referral center. Baseline characteristics, laboratory values, and medical comorbidities were compared to CD patients who presented at the same center and subjects enrolled in NHANES.

RESULTS

Eighty-four PWAWGs were identified and compared to 585 CD patients and 2,686 NHANES patients. Thirty-two alternative diagnoses were made in 25 (30%) PWAWGs, including small intestinal bacterial overgrowth and fructose/lactose intolerance. When compared to patients with CD, PWAWGs had similar body mass index (BMI, 23.1 vs. 23.5, p = 0.54) and mean hemoglobin value (13.4 vs. 13.3, p = 0.6). When compared to male and female patients in NHANES, BMI, folate, and mean hemoglobin values were lower in PWAWGs. Both male and female PWAWGs had a lower prevalence of hypertension.

CONCLUSION

While there are similarities between CD and PWAWGs that could possibly be due to shared HLA haplotypes or an effect of the gluten-free diet, alternative diagnoses are common in these patients. PWAWGs have a similar cardiovascular profile as CD patients in terms of lower BMI and lower prevalence of hypertension.

An Italian prospective multicenter survey on patients suspected of having non-celiac gluten sensitivity

BACKGROUND

Non-celiac gluten sensitivity (NCGS) is still an undefined syndrome with several unsettled issues despite the increasing awareness of its existence. We carried out a prospective survey on NCGS in Italian centers for the diagnosis of gluten-related disorders, with the aim of defining the clinical picture of this new syndrome and to establish roughly its prevalence compared with celiac disease.

METHODS

From November 2012 to October 2013, 38 Italian centers (27 adult gastroenterology, 5 internal medicine, 4 pediatrics, and 2 allergy) participated in this prospective survey. A questionnaire was used in order to allow uniform and accurate collection of clinical, biochemical, and instrumental data.

RESULTS

In total, 486 patients with suspected NCGS were identified in this 1-year period. The female/male ratio was 5.4 to 1, and the mean age was 38 years (range 3-81). The clinical picture was characterized by combined gastrointestinal (abdominal pain, bloating, diarrhea and/or constipation, nausea, epigastric pain, gastroesophageal reflux, aphthous stomatitis) and systemic manifestations (tiredness, headache, fibromyalgia-like joint/muscle pain, leg or arm numbness, 'foggy mind,' dermatitis or skin rash, depression, anxiety, and anemia). In the large majority of patients, the time lapse between gluten ingestion and the appearance of symptoms varied from a few hours to 1 day. The most frequent associated disorders were irritable bowel syndrome (47%), food intolerance (35%) and IgE-mediated allergy (22%). An associated autoimmune disease was detected in 14% of cases. Regarding family history, 18% of our patients had a relative with celiac disease, but no correlation was found between NCGS and positivity for HLA-DQ2/-DQ8. IgG anti-gliadin antibodies were detected in 25% of the patients tested. Only a proportion of patients underwent duodenal biopsy; for those that did, the biopsies showed normal intestinal mucosa (69%) or mild increase in intraepithelial lymphocytes (31%). The ratio between suspected NCGS and new CD diagnoses, assessed in 28 of the participating centers, was 1.15 to 1.

CONCLUSIONS

This prospective survey shows that NCGS has a strong correlation with female gender and adult age. Based on our results, the prevalence of NCGS seems to be only slightly higher than that of celiac disease.

The role of diet on intestinal microbiota metabolism: downstream impacts on host immune function and health, and therapeutic implications

Dietary impacts on health may be one of the oldest concepts in medicine; however, only in recent years have technical advances in mass spectroscopy, gnotobiology, and bacterial sequencing enabled our understanding of human physiology to progress to the point where we can begin to understand how individual dietary components can affect specific illnesses. This review explores the current understanding of the complex interplay between dietary factors and the host microbiome, concentrating on the downstream implications on host immune function and the pathogenesis of disease. We discuss the influence of the gut microbiome on body habitus and explore the primary and secondary effects of diet on enteric microbial community structure. We address the impact of consumption of non-digestible polysaccharides (prebiotics and fiber), choline, carnitine, iron, and fats on host health as mediated by the enteric microbiome. Disease processes emphasized include non-alcoholic fatty liver disease/non-alcoholic steatohepatitis, IBD, and cardiovascular disease/atherosclerosis. The concepts presented in this review have important clinical implications, although more work needs to be done to develop fully and validate potential therapeutic approaches. Specific dietary interventions offer exciting potential for nontoxic, physiologic ways to alter enteric microbial structure and metabolism to benefit the natural history of many intestinal and systemic disorders.

Celiac disease or non-celiac gluten sensitivity? An approach to clinical differential diagnosis

OBJECTIVES

Differentiating between celiac disease (CD) and non-celiac gluten sensitivity (NCGS) is important for appropriate management but is often challenging.

METHODS

We retrospectively reviewed records from 238 patients who presented for the evaluation of symptoms responsive to gluten restriction without prior diagnosis or exclusion of CD. Demographics, presenting symptoms, serologic, genetic, and histologic data, nutrient deficiencies, personal history of autoimmune diseases, and family history of CD were recorded. NCGS was defined as symptoms responsive to a gluten-free diet (GFD) in the setting of negative celiac serology and duodenal biopsies while on a gluten-containing diet or negative human leukocyte antigen (HLA) DQ2/DQ8 testing.

RESULTS

Of the 238 study subjects, 101 had CD, 125 had NCGS, 9 had non-celiac enteropathy, and 3 had indeterminate diagnosis. CD subjects presented with symptoms of malabsorption 67.3% of the time compared with 24.8% of the NCGS subjects (P<0.0001). In addition, CD subjects were significantly more likely to have a family history of CD (P=0.004), personal history of autoimmune diseases (P=0.002), or nutrient deficiencies (P<0.0001). The positive likelihood ratio for diagnosis of CD of a >2× upper limit of normal IgA trans-glutaminase antibody (tTG) or IgA/IgG deaminated gliadan peptide antibody (DGP) with clinical response to GFD was 130 (confidence interval (CI): 18.5-918.3). The positive likelihood ratio of the combination of gluten-responsive symptoms and negative IgA tTG or IgA/IgG DGP on a regular diet for NCGS was 9.6 (CI: 5.5-16.9). When individuals with negative IgA tTG or IgA/IgG DGP also lacked symptoms of malabsorption (weight loss, diarrhea, and nutrient deficiencies) and CD risk factors (personal history of autoimmune diseases and family history of CD), the positive likelihood ratio for NCGS increased to 80.9.

CONCLUSIONS

On the basis of our findings, we have developed a diagnostic algorithm to differentiate CD from NCGS. Subjects with negative celiac serologies (IgA tTG or IgA/IgG DGP) on a regular diet are unlikely to have CD. Those with negative serology who also lack clinical evidence of malabsorption and CD risk factors are highly likely to have NCGS and may not require further testing. Those with equivocal serology should undergo HLA typing to determine the need for biopsy.

Irritable bowel syndrome: Emerging paradigm in pathophysiology

Irritable bowel syndrome (IBS) is one of the most common gastrointestinal disorders, characterized by abdominal pain, bloating, and changes in bowel habits. These symptoms cannot be explained by structural abnormalities and there is no specific laboratory test or biomarker for IBS. Therefore, IBS is classified as a functional disorder with diagnosis dependent on the history taking about manifested symptoms and careful physical examination. Although a great deal of research has been carried out in this area, the pathophysiology of IBS is complex and not completely understood. Multiple factors are thought to contribute to the symptoms in IBS patients; altered gastrointestinal motility, visceral hypersensitivity, and the brain-gut interaction are important classical concepts in IBS pathophysiology. New areas of research in this arena include inflammation, postinfectious low-grade inflammation, genetic and immunologic factors, an altered microbiota, dietary factors, and enteroendocrine cells. These emerging studies have not shown consistent results, provoking controversy in the IBS field. However, certain lines of evidence suggest that these mechanisms are important at least a subset of IBS patients, confirming that IBS symptoms cannot be explained by a single etiological mechanism. Therefore, it is important to keep in mind that IBS requires a more holistic approach to determining effective treatment and understanding the underlying mechanisms.

Advances in coeliac disease

PURPOSE OF REVIEW

To summarize the recent advances in coeliac disease.

RECENT FINDINGS

Details of the polygenic nature of coeliac disease with the human leukocyte antigen (HLA) locus as the dominating genetic element have been uncovered. The existence of a large number of non-HLA coeliac disease genes, only partly shared by each individual patient, suggests the genetic heterogeneity of the disease. The critical role for HLA-DQ-restricted CD4 T cells recognizing antigenic gluten peptides is further substantiated. Involvement of CD8 T cells has received new attention. Other components of wheat than gluten, in particular the amylase trypsin inhibitors, may also play a role. The disease is becoming more prevalent. New guidelines state that coeliac disease diagnosis in children can be made on the basis of clinical signs, serology and genetics without the need of biopsy. The clinical entity 'noncoeliac gluten sensitivity' has received much attention, but diagnostic and pathophysiological definitions are still elusive. The risk for mortality and morbidity in coeliac disease is less than previously thought.

SUMMARY

Our understanding of the basic and clinical aspects of coeliac disease increases. Coeliac disease stands out as a major health problem of almost global occurrence. Case finding, distinguishing coeliac disease from other gluten-sensitive conditions, better care and balanced use of resources are the current challenges.

Irritable bowel syndrome: the role of food in pathogenesis and management

Irritable bowel syndrome (IBS) is a common functional gastrointestinal disorder that affects approximately 10% to 20% of the general adult population in Europe and the Americas and is characterized by abdominal pain and altered bowel habits in the absence of reliable biomarkers. The pathophysiology of IBS is poorly understood and is currently thought to represent a complex interplay among the gut microbiota, low-grade inflammation, impaired mucosal barrier function, visceral hypersensitivity, gut motility, and alterations in the gut-brain axis. In any individual patient, 1 or more of these factors may interact to generate symptoms. Although up to 50% of patients report postprandial exacerbation of symptoms, few studies have critically assessed the role of diet in IBS. Furthermore, although many patients with IBS adopt any one of a host of dietary changes in an attempt to alleviate their symptoms, there has been, up until recently little scientific basis for any dietary recommendation in IBS. This review discusses the contribution of diet to the pathophysiology and symptoms of IBS.

Taste receptors of the gut: emerging roles in health and disease

Recent progress in unravelling the nutrient-sensing mechanisms in the taste buds of the tongue has triggered studies on the existence and role of chemosensory cells in the gut. Indeed, the gastrointestinal tract is the key interface between food and the human body and can sense basic tastes in much the same way as the tongue, through the use of similar G-protein-coupled taste receptors. These receptors 'taste' the luminal content and transmit signals that regulate nutrient transporter expression and nutrient uptake, and also the release of gut hormones and neurotransmitters involved in the regulation of energy and glucose homeostasis. Hence, they play a prominent role in the communication between the lumen, epithelium, smooth muscle cells, afferent nerve fibres and the brain to trigger adaptive responses that affect gastrointestinal function, food intake and glucose metabolism. This review summarises how sensing of nutrients by taste receptors along the gut plays a key role in the process of digestion, and how disturbances or adaptations of these chemosensory signalling pathways may contribute to the induction or resolution of a number of pathological conditions related to diabetes, obesity, or diet-induced symptom generation in irritable bowel syndrome. Targeting these receptors may represent a promising novel route for the treatment of a number of these diseases.

Irritable Bowel Syndrome: Peripheral Mechanisms and Therapeutic Implications

Irritable bowel syndrome (IBS) is the most common functional gastrointestinal disorder, affecting about 10 to 20% of the population in developed countries. The mechanisms underlying the symptoms of this condition are poorly understood. Considered initially as the consequence of abnormal gut motility, visceral hypersensitivity, psychosocial factors and brain-gut axis dysfunction, IBS is now acknowledged as a multifactorial disorder. Specific peripheral mechanisms are involved, including mucosal immune activation, increased intestinal permeability, entero-endocrine cell products, an excess of bile acids, gut dysbiosis. A better understanding of these mechanisms could help develop new and specific therapeutic pathways in patients suffering from IBS.