2015 James W. Freston Single Topic Conference: A Renaissance in the Understanding and Management of Irritable Bowel Syndrome

Epigenetic modulation of visceral nociception

Epigenetics is a process that alters gene activity or phenotype without any changes in the underlying DNA sequence or genotype. These biological changes may have deleterious effects and can lead to various human diseases. Ongoing research is continuing to illuminate the role of epigenetics in a variety of pathophysiologic processes. Several categories of epigenetic mechanisms have been studied including chromatin remodeling, DNA methylation, histone modification, and non-coding RNA mechanisms. These epigenetic changes can have a long-term effect on gene expression without any underlying changes in the DNA sequences. The underlying pathophysiology of disorders of brain-gut interaction and stress-induced visceral pain are not fully understood and the role of epigenetic mechanisms in these disorders are starting to be better understood. Current work is underway to determine how epigenetics plays a role in the neurobiology of patients with chronic visceral pain and heightened visceral nociception. More recently, both animal models and human studies have shown how epigenetic regulation modulates stress-induced visceral pain. While much more work is needed to fully delineate the mechanistic role of epigenetics in the neurobiology of chronic visceral nociception, the current study by Louwies et al., in Neurogastroenterology and Motility provides additional evidence supporting the involvement of epigenetic alterations in the central nucleus of the amygdala in stress-induced visceral hypersensitivity in rodents.

[Irritable bowel syndrome: Role of gut microbiota]

Irritable Bowel Syndrome (IBS) is a functional disorder of the gastrointestinal tract with high prevalence. IBS, in particular the diarrheic subtype, is associated with alterations in gut microbiota composition and functionality, called dysbiosis. However, the treatment of this disease mainly relies on the patient's symptoms without considering the gut microbiota perturbations. In this review, we present epidemiological data about IBS-D. Then, we describe the main pathophysiological mechanisms associated with this disease, by focusing on gut microbiota alterations. We end up discussing the current therapies now available.

Randomised placebo-controlled trial of dietary glutamine supplements for postinfectious irritable bowel syndrome

BACKGROUND

More effective treatments are needed for patients with postinfectious, diarrhoea-predominant, irritable bowel syndrome (IBS-D). Accordingly, we conducted a randomised, double-blind, placebo-controlled, 8-week-long trial to assess the efficacy and safety of oral glutamine therapy in patients who developed IBS-D with increased intestinal permeability following an enteric infection.

METHODS

Eligible adults were randomised to glutamine (5 g/t.i.d.) or placebo for 8 weeks. The primary end point was a reduction of ≥50 points on the Irritable Bowel Syndrome Severity Scoring System (IBS-SS). Secondary endpoints included: raw IBS-SS scores, changes in daily bowel movement frequency, stool form (Bristol Stool Scale) and intestinal permeability.

RESULTS

Fifty-four glutamine and 52 placebo subjects completed the 8-week study. The primary endpoint occurred in 43 (79.6%) in the glutamine group and 3 (5.8%) in the placebo group (a 14-fold difference). Glutamine also reduced all secondary endpoint means: IBS-SS score at 8 weeks (301 vs 181, p<0.0001), daily bowel movement frequency (5.4 vs 2.9±1.0, p<0.0001), Bristol Stool Scale (6.5 vs 3.9, p<0.0001) and intestinal permeability (0.11 vs 0.05; p<0.0001). 'Intestinal hyperpermeability' (elevated urinary lactulose/mannitol ratios) was normalised in the glutamine but not the control group. Adverse events and rates of study-drug discontinuation were low and similar in the two groups. No serious adverse events were observed.

CONCLUSIONS

In patients with IBS-D with intestinal hyperpermeability following an enteric infection, oral dietary glutamine supplements dramatically and safely reduced all major IBS-related endpoints. Large randomised clinical trials (RCTs) should now be done to validate these findings, assess quality of life benefits and explore pharmacological mechanisms.

TRIAL REGISTRATION NUMBER

NCT01414244; Results.

Personalized medicine in functional gastrointestinal disorders: Understanding pathogenesis to increase diagnostic and treatment efficacy

There is overwhelming evidence that functional gastrointestinal disorders (FGIDs) are associated with specific mechanisms that constitute important targets for personalized treatment. There are specific mechanisms in patients presenting with functional upper gastrointestinal symptoms (UGI Sx). Among patients with UGI Sx, approximately equal proportions (25%) of patients have delayed gastric emptying (GE), reduced gastric accommodation (GA), both impaired GE and GA, or neither, presumably due to increased gastric or duodenal sensitivity. Treatments targeted to the underlying pathophysiology utilize prokinetics, gastric relaxants, or central neuromodulators. Similarly, specific mechanisms in patients presenting with functional lower gastrointestinal symptoms, especially with diarrhea or constipation, are recognized, including at least 30% of patients with functional constipation pelvic floor dyssynergia and 5% has colonic inertia (with neural or interstitial cells of Cajal loss in myenteric plexus); 25% of patients with diarrhea-predominant irritable bowel syndrome (IBSD) has evidence of bile acid diarrhea; and, depending on ethnicity, a varying proportion of patients has disaccharidase deficiency, and less often sucrose-isomaltase deficiency. Among patients with predominant pain or bloating, the role of fermentable oligosaccharides, disaccharides, monosaccharides and polyols should be considered. Personalization is applied through pharmacogenomics related to drug pharmacokinetics, specifically the role of CYP2D6, 2C19 and 3A4 in the use of drugs for treatment of patients with FGIDs. Single mutations or multiple genetic variants are relatively rare, with limited impact to date on the understanding or treatment of FGIDs. The role of mucosal gene expression in FGIDs, particularly in IBS-D, is the subject of ongoing research. In summary, the time for personalization of FGIDs, based on deep phenotyping, is here; pharmacogenomics is relevant in the use of central neuromodulators. There is still unclear impact of the role of genetics in the management of FGIDs.

AAPT Diagnostic Criteria for Chronic Abdominal, Pelvic, and Urogenital Pain: Irritable Bowel Syndrome

In conjunction with the Analgesic, Anesthetic, and Addiction Clinical Trial Translations, Innovations, Opportunities, and Networks public-private partnership with the U.S. Food and Drug Administration and the American Pain Society, the Analgesic, Anesthetic, and Addiction Clinical Trial Translations, Innovations, Opportunities, and Networks-American Pain Society Pain Taxonomy (AAPT) initiative strove to develop the characteristics of a diagnostic system useful for clinical and research purposes across disciplines and types of chronic pain conditions. After the establishment of these characteristics, a working group of clinicians and clinical and basic scientists with expertise in abdominal, pelvic, and urogenital pain began generating core diagnostic criteria and defining the related extraintestinal somatic pain and other symptoms experienced by patients. Systematic diagnostic criteria for several common abdominal, pelvic, and urogenital pain conditions are in development. In this report, we present the proposed AAPT criteria for irritable bowel syndrome (IBS), the most common chronic, noncancer abdominal pain condition. A systematic review and synthesis was conducted to complement the Rome IV Diagnostic Criteria for IBS. Future efforts will subject these proposed AAPT criteria to systematic empirical evaluation of their feasibility, reliability, and validity. The AAPT IBS criteria are part of an evidence-based classification system that provides a consistent vocabulary regarding diagnostic criteria, common features, comorbidities, consequences, and putative mechanisms of the disorder. A similar approach is being applied to other chronic and often debilitating abdominal, pelvic, and urogenital pain conditions.

PERSPECTIVE

The AAPT's goal is to develop an evidence-based taxonomy for chronic pain on the basis of a consistently applied multidimensional framework, and encourage experts to apply this taxonomy to specific chronic pain conditions. In this report, the taxonomy is applied to IBS, a chronic abdominal pain condition.