Irritable bowel syndrome: recent and novel therapeutic approaches

Probiotic effects on anxiety-like behavior in animal models

Gut microbiota have been shown to be useful in treating gastrointestinal diseases, cancer, obesity, infections, and, more recently, neuropsychiatric conditions such as degenerative diseases and depression. There has also been recent expansion in testing probiotics and prebiotics on anxiety-like behaviors in animals. Current results indicate that probiotic substances of the Lactobacillus and Bifidobacterium type are effective in reducing anxiety-like behaviors in mice or rats evaluated in the elevated plus-maze, the open-field, the light-dark box, and conditioned defensive burying. Probiotics are also effective in reducing serum or plasma corticosterone levels after acute stress. It is hypothesized that probiotics cause anxiolytic-like effects via vagal influences on caudal solitary nucleus, periaqueductal gray, central nucleus of the amygdala, and bed nucleus of the stria terminalis. Further experimentation is needed to trace the neurochemical anatomy underlying anxiolytic-like behaviors of gut microbiata exerting effects via vagal or nonvagal pathways.

Review article: current and future treatment approaches for pain in IBS

BACKGROUND

Abdominal pain is a core symptom of IBS and a primary driver of care seeking. Visceral hypersensitivity is a key pathophysiological mechanism and therapeutic target for pain in IBS, with components of peripheral and central sensitisation and psychological factors.

AIM

To review current and future treatment approaches specifically for the pain component of IBS.

METHODS

Pubmed search terms included combinations of irritable bowel, pain, visceral hypersensitivity, novel, new, emerging, future and advances.

RESULTS

Established non-pharmacological treatments for IBS pain include the low FODMAP diet, probiotics and psychological interventions, especially hypnotherapy. Tricyclics remain the best evidenced pharmacological approach with GCC agonists, tenapanor, lubiprostone, eluxadoline and 5HT3 antagonists second line according to patient characteristics and availability. Less well-evidenced current options include anti-spasmodics, peppermint oil, SSRIs, SNRIs, alpha 2 delta ligands, melatonin and histamine antagonists. Patients are vulnerable to iatrogenesis and harmful approaches to be avoided include opioids and unwarranted surgical interventions. For severe pain, the concept of augmentation with combined gut-brain neuromodulators and psychotherapy in a multi-disciplinary setting is considered. A plethora of molecular targets and ligands are emerging from pre-clinical studies, together with early clinical evidence for a range of pharmacological, dietary, neurostimulation and novel psychological treatment delivery methods which are reviewed. The history of such emerging approaches, however, merits both caution and optimism in equal measure.

CONCLUSIONS

Despite good in-roads and emerging options, the management of abdominal pain remains one of the biggest challenges and research priorities for patients with IBS.

A Mini Review on Characteristics and Analytical Methods of Otilonium Bromide

Irritable bowel syndrome (IBS) is a world-wide disease prevalently in Western nations. It influences about 15% of the western populace, with a negative effect on the quality of life and furthermore on medical services costs. Anticholinergic antispasmodics are first line of treatment for discomfort or abdominal pain, particularly if unrelieved after alleviation of stoppage or antidiarrheal treatment. Otilonium bromide (OTB) is quaternary ammonium compound with action on distal GI tract as antispasmodic. It is utilized in the treatment of patients influenced by Irritable inside disorder (IBS) because of its particular pharmacokinetic and pharmacodynamic properties. OTB is poorly absorbed systematically was viable in contrast with different medications used for same purpose, for example, pinaverium bromide and mebeverine, with a good tolerability profile. The effects are long lasting, even after stopping the dosage regime for reduction of abdominal pain. In this review, an overview of mechanism of action, pharmacologic action, synthesis and particularly various analytical and bioanalytical methods are discussed. The analytical methods discussed are spectrophotometry including Near Infrared Spectroscopy (NIRS), chromatography and capillary electrophoresis methods are described with the range, limit of detection and quantification. The paper also provides details of scope of further extension of analytical methods. It was found that most of the analytical methods involves usage of toxic solvents e.g., methanol, acetonitrile, chloroform etc. posing risk to the analyst as well as environment.

Recent advances in pharmacological research on the management of irritable bowel syndrome

Irritable bowel syndrome (IBS), a common gastrointestinal (GI) disorder, is associated with various factors, including lifestyle, infection, stress, intestinal flora, and related diseases. The pharmacotherapeutic stimulation of receptors and downstream signaling pathways is effective in reducing IBS symptoms; however, it is still associated with adverse effects. Various receptors related to GI motility and visceral hypersensitivity should be considered to enhance the benefit/risk ratio of IBS treatments. This review discusses recent pharmacological advances in IBS management. Several receptors related to GI motility and abdominal pain are investigated in various angles. 5-Hydroxytryptamine (5-HT) is an important neurotransmitter that activates the colonic mucosal 5-HT₄ receptor without causing severe cardiovascular adverse effects. The clinical potential of ramosetron for diarrhea-predominant IBS has been suggested because of a lower risk of ischemic colitis than conventional 5-HT₃ receptor antagonists. Toll-like receptors (TLRs), especially TLR2 and TLR4, show a significant effect on the post-infection symptoms and lipopolysaccharide-mediated regulation of GI motility. Histamine is a well-known nitrogenous compound that regulates inflammatory responses and visceral hypersensitivity. Histamine 1 receptor-mediated sensitization of the transient receptor potential vanilloid 1 is associated with IBS. Pharmacological approaches based on these signaling pathways could be useful in the development of novel IBS treatments.

Cannabinoid pharmacology and therapy in gut disorders

Cannabis sp. and their products (marijuana, hashish…), in addition to their recreational, industrial and other uses, have a long history for their use as a remedy for symptoms related with gastrointestinal diseases. After many reports suggesting these beneficial effects, it was not surprising to discover that the gastrointestinal tract expresses endogenous cannabinoids, their receptors, and enzymes for their synthesis and degradation, comprising the so-called endocannabinoid system. This system participates in the control of tissue homeostasis and important intestinal functions like motor and sensory activity, nausea, emesis, the maintenance of the epithelial barrier integrity, and the correct cellular microenvironment. Thus, different cannabinoid-related pharmacological agents may be useful to treat the main digestive pathologies. To name a few examples, in irritable bowel syndrome they may normalize dysmotility and reduce pain, in inflammatory bowel disease they may decrease inflammation, and in colorectal cancer, apart from alleviating some symptoms, they may play a role in the regulation of the cell niche. This review summarizes the main recent findings on the role of cannabinoid receptors, their synthetic or natural ligands and their metabolizing enzymes in normal gastrointestinal function and in disorders including irritable bowel syndrome, inflammatory bowel disease, colon cancer and gastrointestinal chemotherapy-induced adverse effects (nausea/vomiting, constipation, diarrhea).

Melatonin's role as a co-adjuvant treatment in colonic diseases: A review

Melatonin is produced in the pineal gland as well as many other organs, including the enterochromaffin cells of the digestive mucosa. Melatonin is a powerful antioxidant that resists oxidative stress due to its capacity to directly scavenge reactive species, to modulate the antioxidant defense system by increasing the activities of antioxidant enzymes, and to stimulate the innate immune response through its direct and indirect actions. In addition, the dysregulation of the circadian system is observed to be related with alterations in colonic motility and cell disruptions due to the modifications of clock genes expression. In the gastrointestinal tract, the activities of melatonin are mediated by melatonin receptors (MT2), serotonin (5-HT), and cholecystokinin B (CCK2) receptors and via receptor-independent processes. The levels of melatonin in the gastrointestinal tract exceed by 10-100 times the blood concentrations. Also, there is an estimated 400 times more melatonin in the gut than in the pineal gland. Gut melatonin secretion is suggested to be influenced by the food intake. Low dose melatonin treatment accelerates intestinal transit time whereas high doses may decrease gut motility. Melatonin has been studied as a co-adjuvant treatment in several gastrointestinal diseases including irritable bowel syndrome (IBS), constipation-predominant IBS (IBS-C), diarrhea-predominant IBS (IBS-D), Crohn's disease, ulcerative colitis, and necrotizing enterocolitis. The purpose of this review is to provide information regarding the potential benefits of melatonin as a co-adjuvant treatment in gastrointestinal diseases, especially IBS, Crohn's disease, ulcerative colitis, and necrotizing enterocolitis.

An Endogenous Tachykinergic NK2/NK3 Receptor Cascade System Controlling the Release of Serotonin from Colonic Mucosa

5-Hydroxytryptamine (5-HT) released from colonic mucosal enterochromaffin (EC) cells is a major signaling molecule, which participates in the pathophysiological regulation of colonic functions in gut disorder including irritable bowel syndrome (IBS), but the endogenous modulator system for the 5-HT release is not yet well elucidated. Our in vitro studies in guinea-pig colon have indicated that the cascade pathway of neuronal tachykinergic NK₃ receptors and NK₂ receptors on peptide YY (PYY)-containing endocrine L cells represents an endogenous modulator system for 5-HT release from EC cells and that melatonin, endogenous tachykinins and PYY play important roles in modulation of the release of 5-HT from EC cells via the endogenous NK₂/NK₃ receptor cascade system. This review aims at examining the potential role of the endogenous tachykinergic NK2/NK3 receptor cascade system controlling the release of 5-HT from EC cells, with special attention being paid to the pathophysiology of gut disorders including IBS.

Comparison of the Effects of pH-Dependent Peppermint Oil and Synbiotic Lactol (Bacillus coagulans + Fructooligosaccharides) on Childhood Functional Abdominal Pain: A Randomized Placebo-Controlled Study

Background:

Still there is no consensus on the best treatment for abdominal pain-related functional Gastrointestinal Disorders (FGIDs).

Objectives:

The purpose of this study was to compare the effects of a synbiotic Lactol (Bacillus coagulans + fructooligosaccharide (FOS)), peppermint oil (Colpermin) and placebo (folic acid) on abdominal pain-related FGIDs except for abdominal migraine.

Patients and Methods:

This placebo-controlled study was conducted on 120 children aged 4 - 13 years to compare the efficacy of pH-dependent peppermint oil (Colpermin) versus synbiotic Lactol (Bacillus coagulans + fructooligosaccharids (FOS)) in decreasing duration, severity and frequency of functional abdominal pain. The patients were randomly allocated into three equal groups (n = 40 in each group) and each group received Colpermin or Lactol or placebo.

Results:

Eighty-eight out of 120 enrolled patients completed a one-month protocol and analyses were performed on 88 patients’ data. Analyses showed that improvement in pain duration, frequency and severity in the Colpermin group was better than the placebo group (P = 0.0001, P = 0.0001 and P = 0.001, respectively). Moreover, pain duration and frequency were decreased in the Lactol group more than the placebo (P = 0.012 and P = 0.0001, respectively), but changes in pain severity were not significant (P = 0.373). Colpermin was superior to Lactol in decreasing pain duration and severity (P = 0.040 and P = 0.013, respectively). No known side effects or intolerance were seen with Colpermin or Lactol.

Conclusions:

The pH-dependent peppermint oil capsule and Lactol tablet (Bacillus coagulans+ FOS) as synbiotics seem to be superior to placebo in decreasing the severity, duration and frequency of pain in abdominal pain-related functional GI disorders.

5-HT7 receptor signaling: improved therapeutic strategy in gut disorders

Serotonin (5-hydroxytryptamine; 5-HT) is most commonly known for its role as a neurotransmitter in the central nervous system (CNS). However, the majority of the body’s 5-HT is produced in the gut by enterochromaffin (EC) cells. Alterations in 5-HT signaling have been associated with various gut disorders including inflammatory bowel disease (IBD), irritable bowel syndrome (IBS) and enteric infections. Recently, our studies have identified a key role for 5-HT in the pathogenesis of experimental colitis. 5-HT₇ receptors are expressed in the gut and very recently, we have shown evidence of 5-HT₇ receptor expression on intestinal immune cells and demonstrated a key role for 5-HT₇ receptors in generation of experimental colitis. This review summarizes the key findings of these studies and provides a comprehensive overview of our current knowledge of the 5-HT₇ receptor in terms of its pathophysiological relevance and therapeutic potential in intestinal inflammatory conditions, such as IBD.

Irritable bowel syndrome: focus on otilonium bromide

Irritable bowel syndrome is a prevalent and chronic disorder, characterized by recurrent abdominal pain/discomfort, bloating and altered bowel habits. This condition affects an estimated 10-15% of the population worldwide and impacts heavily on a patient's daily life and ability to work, as well as healthcare resource utilization. Drug therapy aimed at correcting the primary symptoms of diarrhea/constipation/bloating may have little effect on abdominal pain, which results from visceral hypersensitivity. Smooth muscle relaxants or antispasmodics decrease the tone and contractility of intestinal smooth muscle, effectively managing abdominal pain. Otilonium bromide has been widely used worldwide and has been found to be safe and well tolerated, and superior to placebo for the reduction of symptoms and the prevention of symptom relapse in patients with irritable bowel syndrome.

Constella™(EU)-Linzess™(USA): the last milestone in the long journey of the peptide linaclotide and its implications for the future of peptide drugs

Irritable bowel syndrome with constipation (IBS-C) and chronic idiopathic constipation (CIC) are highly prevalent gastrointestinal disorders associated with health, economical and social problems. Recently, after a long journey of preclinical studies and clinical trials, linaclotide, a first-in-class GC-C receptor peptide agonist, has received the approval in the USA and Europe for the treatment of IBS-C and CIC. This article provides an overview of clinical, economic and biological aspects of IBS-C and CIC and covers the current and emerging therapeutic agents for treating these conditions. Particularly, the pharmacodynamic and pharmacokinetic properties of linaclotide, a small, disulfide-rich peptide, and its implications in the future of peptide drug discovery and development are discussed.

The cannabinoid-1 receptor inverse agonist taranabant reduces abdominal pain and increases intestinal transit in mice

BACKGROUND

Constipation-predominant irritable bowel syndrome (IBS-C) is a common functional gastrointestinal (GI) disorder with abdominal pain and decreased motility. Current treatments of IBS-C are insufficient. The aim of this study was to evaluate the potential application of taranabant, a cannabinoid type 1 (CB1) inverse agonist using mouse models mimicking the symptoms of IBS-C.

METHODS

Changes in intestinal contractile activity were studied in vitro, using isolated mouse ileum and colon and intracellular recordings. In vivo, whole gastrointestinal transit (WGT) and fecal pellet output (FPO) were measured under standard conditions and with pharmacologically delayed GI transit. The antinociceptive effect was evaluated in mustard oil- and acetic acid-induced models of visceral pain. Forced swimming and tail suspension tests were performed and locomotor activity was measured to evaluate potential central side effects.

KEY RESULTS

In vitro, taranabant (10(-10) -10(-7) mol L(-1)) increased contractile responses in mouse ileum and blocked the effect of the CB agonist WIN 55,212-2. Taranabant had no effect on the amplitude of electrical field stimulation (EFS)-evoked junction potentials. In vivo, taranabant (0.1-3 mg kg(-1), i.p. and 3 mg kg(-1), p.o.) increased WGT and FPO in mice and reversed experimental constipation. The effect of taranabant was absent in CB1(-/-) mice. Taranabant significantly decreased the number of pain-related behaviors in animal models. At the doses tested, taranabant did not display mood-related adverse side effects typical for CB1 receptor inverse agonists.

CONCLUSIONS & INFERENCES

Taranabant improved symptoms related to slow GI motility and abdominal pain and may become an attractive template in the development of novel therapeutics targeting IBS-C.

Seasonal patterns of abdominal pain consultations among adults and children

BACKGROUND AND AIM

Consultations for chronic abdominal pain are frequent in adults and children. A seasonal pattern of abdominal pain consultations with winter predominance was shown in previous pediatric studies; however, no studies have investigated whether such a pattern exists in adult patients. Understanding the differences in seasonal patterns of abdominal pain consultations among adults and children may indicate that either different mechanisms exist for common chronic pain conditions or triggering factors may vary by age. The aim of the study was to investigate whether a seasonal variation in abdominal pain consultation patterns exists among adults and children.

METHODS

The number of outpatient consultations among children (5-17 years) and adults (18 years or older) with a diagnosis of abdominal pain of nonspecified origin (International Classification of Diseases-9 code 789.0) from May 2000 to December 2008 was identified in an administrative claims database. The primary outcome measure was the rate of abdominal pain consultations (total number of abdominal pain consultations/total number of distinct patients by month×1000) by season in children and adults. Seasons were defined as follows: winter (December-February), spring (March-May), summer (June-August), and fall (September-November). A trend test was conducted to determine the degree of linearity in the patterns between the 2 groups. Among children, subanalyses by age 5 to 11 years and 12 to 17 years and sex were conducted.

RESULTS

A total of 172.4 million distinct patients (13.4% children, 87.6% adults) were identified in the database between May 2000 and December 2008. During the same time period, 15.6 million patient consultations for abdominal pain were identified (10.1% children, 89.9% adults). Children demonstrated a seasonal pattern in abdominal pain consultations, which best fit a quadratic regression curve, with consultations less common during the summer months. Abdominal pain consultations in adults were linear with no seasonal predominance. The trend in seasonal variation of abdominal pain consultations among children stratified by age and sex remained consistent with the overall child population.

CONCLUSIONS

Abdominal pain consultations in children are less common during summer months, whereas no evidence of seasonal pattern of consultation was found in adults. Factors involved in the pathogenesis of abdominal pain in adults and children may differ.

Effect of electro-acupuncture at different acupoints on neuropeptide and somatostatin in rat brain with irritable bowel syndrome

OBJECTIVE

To compare the regulatory effects of electro-acupuncture (EA) at acupoints Zusanli (ST36) and Hegu (LI4) on the visceral hyper-sensitivity in the rat model of irritable bowel syndrome (IBS), and to explore the acting targets and specialty of acupoints.

METHODS

Except 8 rats of the normal control group, the rest 32 rats were prepared to set up the IBS models. IBS animal model was prepared by enema with acetic acid. Model rats were divided into three groups. Except for rats in the model group for control, those in the other two groups were treated 20 min by EA on ST36 (EA-ST36) and LI4 (EA-LI4) respectively for 2 weeks to observe the effect on behavior response of viscera sensitivity. The changes of neuropeptide (NPY), the somatostatin (SS) levels in blood and tissues of brain and intestine were monitored as well.

RESULTS

The volume thresholds for abdomen uplifting and back hunching were obviously increased after EA-ST36 (P<0.05), but showed insignificant change after EA-LI4. NPY contents lowered and SS contents increased in model rats; both EA-ST36 and EA-LI4 could raise the level of thalamic NPY (P<0.01 and P<0.05, respectively), but showed insignificant effects on NPY in colonic tissue. As for SS content, its colonic level could be reduced by EA-S36 and EA-LI4 (P<0.01 and P<0.05, respectively), however, its blood level was affected only by EA-ST36 (P<0.05).

CONCLUSIONS

EA-ST36 or EA-LI4 could regulate the NPY in thalamus and SS in colonic tissue, the former could affect blood level of SS as well. It is deemed that NPY and SS may be the key substances for regulating the action of acupuncture in the brain-intestinal axis; their different levels could be regarded as an indicator for the functional difference between the acupoints.

Prevalence of restless legs syndrome in patients with irritable bowel syndrome

AIM: To determine the prevalence of restless legs syndrome (RLS) in patients with irritable bowel syndrome (IBS).

METHODS: Patients with diarrhea-predominant IBS (n = 30), constipation-predominant IBS (n = 30), or mixed-symptom IBS (n = 30) were recruited from the community between March 2008 and February 2009. Rifaximin 200 mg three times daily was administered empirically to alleviate small intestinal bowel overgrowth in all patients. The presence of RLS was assessed via an RLS questionnaire and polysomnography.

RESULTS: Twenty-six patients with IBS (29%) were diagnosed with RLS using the RLS questionnaire. Twenty-four of the 26 patients (92%) underwent polysomnography, and all had confirmation of RLS. A greater percentage of patients with RLS had diarrhea-predominant IBS (62%) compared with patients with constipation-predominant IBS (4%) or mixed-symptom IBS (33%).

CONCLUSION: Restless legs syndrome is prevalent in patients with IBS, especially those with diarrheal symptoms. Assessment of concomitant disorders may improve diagnosis and expand relevant treatment options for patients.

Analgesic effects of melatonin: a review of current evidence from experimental and clinical studies

Melatonin is an endogenous indoleamine, produced mainly by the pineal gland. Melatonin has been proven to have chronobiotic, antioxidant, antihypertensive, anxiolytic and sedative properties. There are also experimental and clinical data supporting an analgesic role of melatonin. In experimental studies, melatonin shows potent analgesic effects in a dose-dependent manner. In clinical studies, melatonin has been shown to have analgesic benefits in patients with chronic pain (fibromyalgia, irritable bowel syndrome, migraine). The physiologic mechanism underlying the analgesic actions of melatonin has not been clarified. The effects may be linked to G(i) -coupled melatonin receptors, to G(i) -coupled opioid μ-receptors or GABA-B receptors with unknown downstream changes with a consequential reduction in anxiety and pain. Also, the repeated administration of melatonin improves sleep and thereby may reduce anxiety, which leads to lower levels of pain. In this paper, we review the current evidence regarding the analgesic properties of melatonin in animals and humans with chronic pain.

Both α2B- and α2C-adrenoceptor subtypes are involved in the mediation of centrally induced gastroprotection in mice

α(2)-adrenoceptors are known to mediate gastroprotective effect in both acid-dependent and acid-independent ulcer models. The aim of the present study was to determine, which of the three α(2)-adrenoceptor subtypes (α(2A), α(2B) or α(2C)) is responsible for this protection. Various α(2)-adrenoceptor agonists and antagonists were administered intracerebroventricularly (i.c.v.) to C57BL/6 mice with deletion of genes encoding the different subtypes. The gastric mucosal damage was induced by orally injected acidified ethanol. Both the non-selective α(2)-adrenoceptor agonist clonidine (0.3-2.8 nmol) and the α(2B/C)-adrenoceptor subtype preferring agonist ST-91 (0.5-11.5 nmol) induced dose-dependent gastroprotective effect in wild type, α(2A)-, α(2B)- and α(2C)-KO mice. In contrast, the α(2A)-adrenoceptor subtype agonist oxymetazoline (0.07-84 nmol i.c.v.) reduced only slightly the development of ethanol-induced ulcers. The effect of clonidine was antagonized by the non-selective antagonist yohimbine (25 nmol) and the α(2B/C)-adrenoceptor antagonist ARC 239 (10.4 nmol), but not by the α(2A)-adrenoceptor antagonist BRL 44408 (7.5 nmol). ARC 239 also reversed the effect of clonidine in α(2A)-, α(2B)- and α(2C)-KO mice, while the selective α(2C)-adrenoceptor antagonist JP 1302 (52 nmol) antagonized that only in α(2B)-KO, but not in α(2A)- and α(2C)-KO mice. These results suggest that α(2B)- and α(2C)-adrenoceptor subtypes can equally contribute to the mediation of gastroprotective effect induced by α(2)-adrenoceptor agonists in mice.

[Irritable bowel syndrome, levator ani syndrome, proctalgia fugax and chronic pelvic and perineal pain]

OBJECTIVES

To define functional gastrointestinal pain, irritable bowel syndrome (IBS), levator ani syndrome, proctalgia fugax, the pathophysiology of these syndromes and the treatments that can be proposed.

MATERIAL AND METHODS

Review of articles published on the theme based on a Medline (PubMed) search and consensus conferences selected according to their scientific relevance.

RESULTS

IBS is very common. Patients report abdominal pain and/or discomfort, bloating, and abnormal bowel habit (diarrhoea, constipation or both), in the absence of any structural or biochemical abnormalities. IBS has a complex, multifactorial pathophysiology, involving biological and psychosocial interactions resulting in dysregulation of the brain-gut axis associated with disorders of intestinal motility, hyperalgesia, immune disorders and disorders of the intestinal bacterial microflora and autonomic and hormonal dysfunction. Many treatments have been proposed, ranging from diet to pharmacology and psychotherapy.

DISCUSSION

Patients with various types of chronic pelvic and perineal pain, especially those seen in urology departments, very often report associated IBS. This syndrome is also part of a global and integrated concept of pelviperineal dysfunction, avoiding a rigorous distinction between the posterior segment and the midline and anterior segments of the perineum.

Pathways connecting cognitive behavioral therapy and change in bowel symptoms of IBS

OBJECTIVE

A single previous paper on this topic found a direct pathway between cognitive behavioral therapy (CBT) and an irritable bowel syndrome (IBS) global symptom score. This is controversial since under the biopsychosocial model, the expectation is that CBT's effect would be mediated by mood. Using more sensitive bowel symptom scales and measurements at additional time points, we aimed to compare the relative strengths of direct pathways between CBT and change in IBS symptoms and indirect pathways that operate via mood state using structural equation modeling.

METHODS

Our data set included 105 people with Rome I IBS randomized to individual CBT (n=34), relaxation therapy (n=36), and usual medical care (n=35). The primary outcome was defined as adequate relief of IBS symptoms in terms of the distress, frequency, and impairment according to the Bowel Symptom Severity Scale. Outcomes in functional status (according to the 36-item Short-Form Health Survey) and psychological status (Hospital Anxiety and Depression Scale) were secondary outcomes.

RESULTS

Our data suggest indirect pathways that operate via mood, most clearly anxiety but to a lesser extent depression. Statistically significant pathways were identified that lead from CBT to change in mood state thence to change in bowel symptoms, followed by further changes in mood then changes in bowel symptoms. Our data provide no evidence of direct effect of CBT on bowel symptoms.

CONCLUSIONS

The present study suggests that CBT may operate via changes in mood state while not ruling out the possibility of direct effects. Our findings do not directly support, but are consistent with, a biopsychosocial model.

Synthesis and biological evaluation of novel peripherally active morphiceptin analogs

Morphiceptin (Tyr-Pro-Phe-Pro-NH(2)), a tetrapeptide present in the enzymatic digest of bovine beta-casein, is a selective ligand of the mu-opioid receptor. In the present study, we describe the synthesis of a series of novel morphiceptin analogs modified in positions 1-3. Two of the obtained analogs, [Dmt(1), D-Ala(2), D-1-Nal(3)]morphiceptin and [Dmt(1), D-NMeAla(2), D-1-Nal(3)]morphiceptin (Dmt-2',6'-dimethyltyrosine and d-1-Nal-3-(1-naphthyl)-D-alanine)) displayed very high mu-receptor affinity, resistance to enzymatic degradation, and remarkable supraspinally mediated analgesia, as shown in the hot-plate test after intracerebroventricular but not intravenous administration, which indicated that they could not cross the blood-brain barrier. Therefore, these two analogs were further tested in vitro and in vivo towards their possible peripheral analgesic activity and inhibitory effect on gastrointestinal (GI) motility. We report that both peptides showed strong antinociceptive effect in the writhing test after intraperitoneal administration, inhibited smooth muscle contractility in vitro and GI motility in vivo. Taken together, these findings indicate that the novel morphiceptin analogs which induce peripheral, but not central antinociception, inhibit GI transit, and possess exceptional metabolic stability, may provide an interesting approach to the development of peripherally restricted agents for the treatment of GI motility disorders, such as diarrhea or diarrhea-predominant irritable bowel syndrome.

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.

Effect of electro-acupuncture on substance P, its receptor and corticotropin-releasing hormone in rats with irritable bowel syndrome

AIM: To investigate the effect and mechanism of electro-acupuncture (EA) at ST25 and ST37 on irritable bowel syndrome (IBS) of rats.

METHODS: A total of 21 male Sprague-Dawley rats were randomly divided into normal group, model group and EA group. A rat model of IBS was established by constraining the limbs and distending the colorectum of rats. Rats in EA group received bilateral EA at ST25 and ST37 with a sparse and intense waveform at a frequency of 2/50 Hz for 15 min, once a day for 7 d as a course. Rats in normal and model groups were stimulated by distending colorectum (CR). An abdominal withdrawal reflex (AWR) scoring system was used to evaluate improvements in visceral hypersensitivity. Toluidine blue-improved method, immunohistochemistry and radioimmunoassay were used to observe mucosal mast cells (MC), changes of substance P (SP) and substance P receptor (SPR) in colon and change of corticotropin-releasing hormone (CRH) in hypothalamus.

RESULTS: The threshold of visceral sense was significantly lower in model group than in normal group, and significantly higher in EA group than in model group. The number of mucosal MC was greater in model group than in normal group and significantly smaller in EA group than in model group. The CRH level in hypothalamus of rats was significantly higher in model group than in normal group, which was remarkably decreased after electro-acupuncture treatment. The SP and SPR expression in colon of rats in model group was decreased after electro-acupuncture treatment.

CONCLUSION: EA at ST25 and ST37 can decrease the number of mucosal MC and down-regulate the expression of CRH in hypothalamus, and the expression of SP and SPR in colon of rats with IBS.

Association of alpha 2A adrenergic receptor gene (ADRAlpha2A) polymorphism with irritable bowel syndrome, microscopic and ulcerative colitis

BACKGROUND

Alpha 2 adrenergic receptors (alpha2 ARs) play a central role in the regulation of systemic sympathetic activity. Prejunctional alpha 2A adrenoceptor regulates through negative feedback at presynaptic nerve ending. A-1291 C>G polymorphism located in alpha2-adrenergic receptor gene (ADRAlpha2A) has been identified. We investigated the possible association between 1291 C>G polymorphism in the promoter region of ADRAlpha2A in clinical subtypes of IBS, ulcerative and microscopic colitis patients.

METHODS

This prospective case control study included 92 patients with diarrhea predominant IBS (D-IBS), 44 with constipation predominant IBS (C-IBS), 15 with alternating diarrhea and constipation IBS (M-IBS), 75 ulcerative colitis (UC), 41 microscopic colitis (MC) and 100 healthy controls. The subjects were genotyped by using PCR amplification of the promoter region of ADRAlpha2A gene followed by digestion with the restriction enzyme MspI. The study was approved by the institute ethical committee.

RESULTS

A strong genotypic association was observed between alpha2A-1291 C>G polymorphism and D-IBS (chi2=6.38, df=2, p<0.05). There was no significant difference in alpha2A-1291 C>G genotype and allele frequency between C-IBS, M-IBS, UC, MC cases and control subjects.

CONCLUSIONS

A significant association was observed between alpha2A-1291C>G polymorphism and D-IBS. Thus, alpha2 AR gene may be a potential candidate involved in the pathophysiology of D-IBS.

Do corticotropin releasing factor-1 receptors influence colonic transit and bowel function in women with irritable bowel syndrome?

Corticotropin releasing factor (CRF), a mediator of stress response, alters gastrointestinal (GI) functions. Stress-related changes in colonic motility are blocked by selective CRF(1) receptor antagonists. Our aim was to assess whether modulation of central and peripheral CRF(1) receptors affects colonic transit and bowel function in female patients with diarrhea-predominant irritable bowel syndrome (D-IBS). This randomized, double-blind, placebo-controlled, 2-wk study evaluated the effects of oral pexacerfont (BMS-562086), a selective CRF(1) receptor antagonist, 25 and 100 mg qd, on GI and colonic transit of solids [by validated scintigraphy with primary end point colonic geometric center (GC) at 24 h] and bowel function (by validated daily diaries) in 39 women with D-IBS. The 100-mg dose was comparable to a dose that inhibited colonic motility in stressed rats. Treatment effects were compared by analysis of covariance with baseline colonic transit as covariate. The study had 80% power (alpha = 0.05) to detect clinically meaningful (26%) differences in colonic transit. Thirty-nine of 55 patients fulfilled eligibility criteria (9 screen failures, 5 baseline GC24 outside prespecified range). At baseline, three treatment groups had comparable age, body mass index, and GC 24 h. Significant effects of pexacerfont relative to placebo were not detected on colonic GC24 (P = 0.53), gastric emptying, orocecal transit, ascending colon emptying half-time, and stool frequency, consistency, and ease of passage. No safety issues were identified. We conclude that in women with D-IBS, pexacerfont, 25 or 100 mg qd, does not significantly alter colonic or other regional transit or bowel function. The role of central and peripheral CRF(1) receptors in bowel function in D-IBS requires further study.

Prophylactic role of maternal administration of probiotics in the prevention of irritable bowel syndrome

Neonatal stress is a common early life event which alters the development of the endocrine and immune systems. Specifically, exposure to neonatal stress results in alterations to the hypothalamic-pituitary-adrenal (HPA) axis resulting in offspring who hyper-respond to stress in adulthood. Recently, this concept has been applied to the ontogeny of functional gastrointestinal (GI) disturbances such as irritable bowel syndrome (IBS). The high prevalence of this disorder and the ineffectiveness of current treatments results in high direct and indirect costs to the society. Recently, administration of probiotics to neonates has been used as a safe and cost-effective preventative strategy to revoke the long term unfavourable imprinting induced on the gastrointestinal system by early life stressors in animal models of human IBS. It is not as yet known however, whether maternal supplementary probiotics may also contribute to improved GI integrity and gut-associated immune functioning in stressed neonates, if these possible improvements persist into adulthood, or how this protective effect may be mediated. Our hypothesis is an attempt to link this proposed nutritional approach and its possible preventive effects against GI dysfunctions provoked by neonatal stress.

Changes in salivary physiological stress markers induced by muscle stretching in patients with irritable bowel syndrome

Background

Psychophysiological processing has been reported to play a crucial role in irritable bowel syndrome (IBS) but there has been no report on modulation of the stress marker chromogranin A (CgA) resulting from muscle stretching. We hypothesized that abdominal muscle stretching as a passive operation would have a beneficial effect on a biochemical index of the activity of the sympathetic/adrenomedullary system (salivary CgA) and anxiety.

Methods

Fifteen control and eighteen untreated IBS subjects underwent experimental abdominal muscle stretching for 4 min. Subjects relaxed in a supine position with their knees fully flexed while their pelvic and trunk rotation was passively and slowly moved from 0 degrees of abdominal rotation to about 90 degrees or the point where the subject reported feeling discomfort.

Changes in the Gastrointestinal Symptoms Rating Scale (GSRS), State Trait Anxiety Inventory (STAI), Self-rating Depression Scale (SDS), ordinate scale and salivary CgA levels were compared between controls and IBS subjects before and after stretching. A three-factor analysis of variance (ANOVA) with period (before vs. after) as the within-subject factor and group (IBS vs. Control), and sex (men vs. female) as the between-subject factors was carried out on salivary CgA.

Results

CgA showed significant interactions between period and groups (F[1, 31] = 4.89, p = 0.03), and between groups and sex (F[1, 31] = 4.73, p = 0.03). Interactions between period and sex of CgA secretion were not shown (F[1, 3] = 2.60, p = 0.12). At the baseline, salivary CgA in IBS subjects (36.7 ± 5.9 pmol/mg) was significantly higher than in controls (19.9 ± 5.5 pmol/mg, p < 0.05). After the stretching, salivary CgA significantly decreased in the IBS group (25.5 ± 4.5 pmol/mg), and this value did not differ from that in controls (18.6 ± 3.9 pmol/mg).

Conclusion

Our results suggest the possibility of improving IBS pathophysiology by passive abdominal muscle stretching as indicated by CgA, a biochemical index of the activity of the sympathetic/adrenomedullary system.

Design of treatment trials in irritable bowel syndrome: opioid agonists and atypical benzodiazepine antagonists

Irritable bowel syndrome (IBS) is a common gastrointestinal disorder characterized by abdominal pain and altered bowel function. Few agents are available for the treatment of IBS. Historically, one impediment to the development of agents to treat IBS was lack of a uniform and robust clinical trial design. Studies occurred with different durations of treatment, endpoints and with different target populations. Great advances have been made over the past decade in trial design including: optimal duration of study, mode of data collection, populations to evaluate and identification of endpoints. Using these refinements, it was possible to demonstrate the efficacy of some new agents. These advances are illustrated by a review of trials with kappa opioid agonists and atypical benzodiazepine antagonists, which appear to be promising new classes of treatments for symptoms in IBS.

Regulation of enteric functions by adenosine: pathophysiological and pharmacological implications

The wide distribution of ATP and adenosine receptors as well as enzymes for purine metabolism in different gut regions suggests a complex role for these mediators in the regulation of gastrointestinal functions. Studies in rodents have shown a significant involvement of adenosine in the control of intestinal secretion, motility and sensation, via activation of A1, A2A, A2B or A3 purinergic receptors, as well as the participation of ATP in the regulation of enteric functions, through the recruitment of P2X and P2Y receptors. Increasing interest is being focused on the involvement of ATP and adenosine in the pathophysiology of intestinal disorders, with particular regard for inflammatory bowel diseases (IBDs), intestinal ischemia, post-operative ileus and related dysfunctions, such as gut dysmotility, diarrhoea and abdominal discomfort/pain. Current knowledge suggests that adenosine contributes to the modulation of enteric immune and inflammatory responses, leading to anti-inflammatory actions. There is evidence supporting a role of adenosine in the alterations of enteric motor and secretory activity associated with bowel inflammation. In particular, several studies have highlighted the importance of adenosine in diarrhoea, since this nucleoside participates actively in the cross-talk between immune and epithelial cells in the presence of diarrhoeogenic stimuli. In addition, adenosine exerts complex regulatory actions on pain transmission at peripheral and spinal sites. The present review illustrates current information on the role played by adenosine in the regulation of enteric functions, under normal or pathological conditions, and discusses pharmacological interventions on adenosine pathways as novel therapeutic options for the management of gut disorders and related abdominal symptoms.

Novel pharmacology: asimadoline, a kappa-opioid agonist, and visceral sensation

Asimadoline is a potent kappa-opioid receptor agonist with a diaryl acetamide structure. It has high affinity for the kappa receptor, with IC(50) of 5.6 nmol L(-1) (guinea pig) and 1.2 nmol L(-1) (human recombinant), and high selectively with kappa : micro : delta binding ratios of 1 : 501 : 498 in human recombinant receptors. It acts as a complete agonist in in vitro assay. Asimadoline reduced sensation in response to colonic distension at subnoxious pressures in healthy volunteers and in irritable bowel syndrome (IBS) patients without alteration of colonic compliance. Asimadoline reduced satiation and enhanced the postprandial gastric volume (in female volunteers). However, there were no significant effects on gastrointestinal transit, colonic compliance, fasting or postprandial colonic tone. In a clinical trial in 40 patients with functional dyspepsia (Rome II), asimadoline did not significantly alter satiation or symptoms over 8 weeks. However, asimadoline, 0.5 mg, significantly decreased satiation in patients with higher postprandial fullness scores, and daily postprandial fullness severity (over 8 weeks); the asimadoline 1.0 mg group was borderline significant. In a clinical trial in patients with IBS, average pain 2 h post-on-demand treatment with asimadoline was not significantly reduced. Post hoc analyses suggest that asimadoline was effective in mixed IBS. In a 12-week study in 596 patients, chronic treatment with 0.5 mg and 1.0 mg asimadoline was associated with adequate relief of pain and discomfort, improvement in pain score and number of pain-free days in patients with IBS-D. The 1.0 mg dose was also efficacious in IBS-alternating. There were also weeks with significant reduction in bowel frequency and urgency. Asimadoline has been well tolerated in human trials to date.

Dose-response effect of a beta3-adrenergic receptor agonist, solabegron, on gastrointestinal transit, bowel function, and somatostatin levels in health

beta(3)-Adrenoceptors(beta(3)-AR) are expressed by cholinergic myenteric neurons and beta(3)-AR agonists are effective in experimental models of diarrhea. Our aim was to explore the effects of a beta(3)-AR agonist, solabegron, on gastrointestinal transit, safety, bowel function, plasma somatostatin, and solabegron pharmacokinetics (PK) following single and multiple doses. In a single-center, double-blind, parallel-group trial, 36 healthy volunteers were randomized to oral solabegron (50 or 200 mg twice daily) or placebo. Transit was measured by a validated method ((99m)Tc-labeled egg meal and (111)In charcoal delivered to the colon via delayed-release capsule). Stool frequency, form, and ease of passage were measured on a validated daily diary; plasma somatostatin by radioimmunoassay and plasma solabegron and its active metabolite by validated liquid chromatography-tandem mass spectroscopy analysis followed by PK analysis using noncompartmental methods. There were no overall or dose-related effects of solabegron on gastric, small bowel, or colonic transit, plasma somatostatin levels, stool frequency, form, or ease of passage in healthy volunteers. Solabegron and active metabolite exposures (area under the curve and maximum serum concentration) at both dose levels were consistent with PK at similar doses in previous phase I studies. We concluded that 7 days of the beta(3)-AR agonist, solabegron, 50 or 200 mg twice daily, did not significantly alter gastrointestinal or colonic transit or bowel function. In this study, medication was generally well tolerated with few adverse events reported and no clinically significant changes in vital signs observed. Further studies on clinical efficacy, visceral sensitivity, and gastrointestinal transit are required in irritable bowel syndrome patients.

The analgesic effect of paeoniflorin on neonatal maternal separation-induced visceral hyperalgesia in rats

Paeoniflorin (PF) is one of the principle active ingredients of the root of Paeonia lactiflora Pall (family Ranunculaceae), a Chinese herb traditionally used to relieve pain, especially visceral pain. The present study aimed to investigate both the effect of PF on neonatal maternal separation-induced visceral hyperalgesia in rats and the mechanism by which such effect is exerted. A dose-dependent analgesic effect was produced by PF (45, 90, 180, and 360 mg/kg i.p.). Centrally administered PF (4.5 mg/kg i.c.v) also produced a significant analgesic effect. The analgesic effect of PF (45 mg/kg i.p.) was maximal at 30 minutes after administration. Furthermore, it was found that nor-binaltorphimine (nor-BNI, 3 mg/kg i.p.), dl-alpha-methyltyrosine (alpha-AMPT, 250 mg/kg i.p.), and yohimbine (3 mg/kg i.p.) could block the analgesic effect of PF (45 mg/kg i.p.). Time course determination of PF in brain nuclei showed that the maximal concentration of PF was 30 minutes after intraperitoneal administration of PF (180 mg/kg) in cerebral nuclei, involving the amygdala, hypothalamus, thalamus, and cortex. These data indicate that PF has an analgesic effect on visceral pain in rats with neonatal maternal separation and that this effect may be mediated by kappa-opioid receptors and alpha(2)-adrenoceptors in the central nervous system.

PERSPECTIVE

This study demonstrates that PF has an analgesic effect on pain in visceral hyperalgesic rats. These results suggest that PF might be potentially useful in clinical therapy for irritable bowel syndrome as a pharmacological agent in alleviating visceral pain.

Efficacy of on-demand asimadoline, a peripheral kappa-opioid agonist, in females with irritable bowel syndrome

BACKGROUND & AIMS

In experimental animal models of irritable bowel syndrome (IBS) and human studies, peripheral kappa opioid agonists have been shown to decrease sensation to colonic distention. The aim of this study was to compare the effects of the kappa opioid agonist, asimadoline, and placebo on episodes of abdominal pain in patients with IBS.

METHODS

After a 2-week run-in period, 100 patients with IBS were randomized (3:2 ratio) to receive asimadoline, up to 1 mg 4 times daily, or placebo for 4 weeks in a double-blind study. Pain was scored by daily diary using a 100-mm visual analogue scale. During pain episodes, patients recorded the pain severity, took study medication, and recorded their pain score 2 hours later. The primary end point was the average reduction in pain severity 2 hours after treatment.

RESULTS

The average pain reduction 2 hours posttreatment was not significantly different between the groups. Post hoc analyses suggest asimadoline was effective in mixed IBS (P = .003, unadjusted), but may be worse in diarrhea-predominant IBS (P = .065 unadjusted). The anxiety score was reduced modestly by asimadoline (P = .053). No significant adverse effects were noted.

CONCLUSIONS

An on-demand dosing schedule of asimadoline was not effective in reducing severity of abdominal pain in IBS. Further studies in visceral pain and IBS appear warranted.

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.

Effect of 5 days linaclotide on transit and bowel function in females with constipation-predominant irritable bowel syndrome

BACKGROUND & AIMS

Oral linaclotide, a novel agonist of guanylate cylase-C, stimulates intestinal fluid secretion and transit, and decreases visceral hypersensitivity in animal studies. In healthy volunteers, linaclotide was safe, well tolerated, increased stool frequency, and decreased stool consistency and time to first bowel movement. This randomized, double-blind, placebo-controlled study evaluated the effects of oral linaclotide, 100 and 1000 microg once daily, in 36 women with constipation-predominant irritable bowel syndrome; colonic transit was normal in >50% patients.

METHODS

Participants underwent 5-day baseline and 5-day treatment periods; gastrointestinal transit (by validated scintigraphy) and bowel function (by daily diaries) were assessed. Treatment effects were compared using analysis of covariance (baseline colonic transit as covariate) with pairwise comparisons of each dose vs placebo.

RESULTS

There was a significant overall treatment effect on ascending colon emptying half-time (P = .015) and overall colonic transit at 48 hours (P = .02) but not overall transit at 24 hours (P = ns), with a significant acceleration by linaclotide 1000 microg vs placebo (P = .004 and P = .01, respectively) but no significant effect of linaclotide 100-microg dose. There were significant overall treatment effects on stool frequency, stool consistency, ease of passage, and time to first bowel movement with a strong dose response for stool consistency (overall, P < .001). No safety issues were identified.

CONCLUSIONS

In women with constipation-predominant irritable bowel syndrome, linaclotide 1000 microg once daily significantly accelerated ascending colonic transit and altered bowel function. Further randomized controlled trials of clinical efficacy of linaclotide are warranted.

How does cognitive behavior therapy for irritable bowel syndrome work? A mediational analysis of a randomized clinical trial

BACKGROUND AND AIMS

Although multiple clinical trials support the efficacy of psychological treatments for reducing irritable bowel syndrome (IBS) symptoms, the mechanisms responsible for symptomatic improvement are unknown. One hypothesis is that psychological treatments work by alleviating comorbid psychological distress implicated in the worsening of bowel symptoms and quality of life. An alternative hypothesis assumes that changes in distress are not strictly a cause but a consequence of IBS that will decrease with symptomatic improvement.

METHODS

We evaluated these 2 hypotheses by applying structural equation modeling (SEM) to the data set of a large number (n = 147) of Rome II diagnosed participants randomized to CBT, psychoeducation, or wait list. Per Rome guidelines, the primary end point was global improvement of gastrointestinal (GI) symptoms measured 2 weeks after a 10-week regimen. Secondary end points were distress and quality of life (QOL).

RESULTS

SEM analyses lend support to a model in which CBT is associated with improvements in IBS symptoms, but that therapeutic gains do not depend on changes in patients' overall level of psychological distress. Symptom severity, but not clinical status (pain catastrophizing, predominant bowel habits, symptom duration, abuse, diagnosable psychiatric disorder) or relevant sociodemographic variables (eg, gender, age), moderated treatment outcome.

CONCLUSION

CBT has a direct effect on global IBS symptom improvement independent of its effects on distress. Improvement in IBS symptoms is associated with improvements in the QOL, which may lower distress. Symptom improvements are not moderated by variables reflecting the mental well-being of IBS patients.

An update on somatostatin receptor signaling in native systems and new insights on their pathophysiology

The peptide somatostatin (SRIF) has important physiological effects, mostly inhibitory, which have formed the basis for the clinical use of SRIF compounds. SRIF binding to its 5 guanine nucleotide-binding proteins-coupled receptors leads to the modulation of multiple transduction pathways. However, our current understanding of signaling exerted by receptors endogenously expressed in different cells/tissues reflects a rather complicated picture. On the other hand, the complexity of SRIF receptor signaling in pathologies, including pituitary and nervous system diseases, may be studied not only as alternative intervention points for the modulation of SRIF function but also to exploit new chemical space for drug-like molecules.

Irritable bowel syndrome

Irritable bowel syndrome (IBS) is a disease of unclear, complex pathophysiology characterised by abdominal pain and discomfort and altered bowel activity. It affects an estimated 10-15% of individuals worldwide and has a large impact on quality of life (QOL) and both direct and indirect healthcare costs. Symptoms of IBS are usually triggered by disruption of gastrointestinal (GI) function secondary to infection, dietary factors, lifestyle changes or psychological stress. While most currently available pharmacological treatments of IBS focus on symptomatic treatment of the syndrome, agents that attempt to address the pathophysiology of the disease, in particular the role of serotonin, have received much attention in recent years. However, there is growing concern that serotonergic agents as a class may be associated with rare, but serious, episodes of ischaemic colitis, with several cases of this complication having been reported in association with use of serotonergic agents that have reached the market. Thus, there remains an important need for safe and effective agents that treat the symptoms of IBS. Otilonium bromide, a spasmolytic agent, has been widely used worldwide and has been found to be effective and safe for managing abdominal pain. Clinical trials indicate that it improves baseline abdominal pain and distension, and is particularly effective in reducing diarrhoea. Combining otilonium bromide with benzodiazepines, such as diazepam, may improve the efficacy of the agent with respect to GI symptoms, while also treating underlying anxiety disorders. More research is required to confirm the efficacy and mechanisms of action associated with this combination therapy in IBS. Safety data from clinical trials and postmarketing sources indicate that otilonium bromide is well tolerated, with a safety profile comparable to placebo in clinical trials and only two reported cases of adverse reactions (urticaria) among 10-year postmarketing data. This article reviews the pathophysiology and treatment of IBS with a particular focus on the role of otilonium bromide in the management of this condition.

Postinfectious irritable bowel syndrome: a long-term consequence of bacterial gastroenteritis

Irritable bowel syndrome (IBS) is a commonly diagnosed disease characterized by gastrointestinal symptoms that may be associated with psychological illness and emotional problems. The prevalence rate worldwide for IBS ranges from 10 to 20% and is higher for women than for men. IBS imposes a substantial financial burden on both patients and employers because of increased medical costs and decreased work productivity. Recent studies indicate that inflammatory processes involving the gastrointestinal tract are strongly correlated with IBS. Acute bacterial gastroenteritis has been linked with the onset of symptoms in approximately 15% of patients diagnosed with IBS; these cases have been called postinfectious IBS. Organisms commonly associated with postinfectious IBS include the foodborne pathogens Campylobacter, Escherichia coli, Salmonella, and Shigella. The pathologic changes associated with postinfectious IBS are likely due to inflammatory reactions induced by the infecting organisms. Postinfectious IBS should be recognized as a potential long-term consequence of foodborne gastroenteritis.

Characterization of the novel human serotonin receptor subunits 5-HT3C,5-HT3D, and 5-HT3E

Within the family of serotonin receptors, the 5-hydroxytryptamine-3 (5-HT(3)) receptor is the only ligand-gated ion channel. It is composed of five subunits, of which the 5-HT(3A) and 5-HT(3B) subunits are best characterized. Several studies, however, have reported on the functional diversity of native 5-HT(3) receptors, which cannot solely be explained on the basis of the 5-HT(3A) and 5-HT(3B) subunits. After our discovery of further putative 5-HT(3) serotonin receptor-encoding genes, HTR3C, HTR3D, and HTR3E, we investigated whether these novel candidates and the isoform 5-HT(3Ea) are able to form functional 5-HT(3) receptor complexes. Using immunofluorescence and immunoprecipitation studies of heterologously expressed proteins, we found that each of the respective candidates coassembles with 5-HT(3A). To investigate whether the novel subunits modulate 5-HT(3) receptor function, we performed radioligand-binding assays and calcium-influx studies in human embryonic kidney 293 cells. Our experiments revealed that the 5-HT(3C),5-HT(3D), 5-HT(3E), and 5-HT(3Ea) subunits alone cannot form functional receptors. Coexpression with 5-HT(3A), however, results in the formation of functional heteromeric complexes with different serotonin efficacies. Potencies of two agonists and antagonists were nearly identical with respect to homomeric 5-HT(3A) and heteromeric complexes. However, 5-HT showed increased efficacy with respect to 5-HT(3A/D) and 5-HT(3A/E) receptors, which is consistent with the increased surface expression compared with 5-HT(3A) receptors. In contrast, 5-HT(3A/C) and 5-HT(3A/Ea) receptors exhibited decreased 5-HT efficacy. These data show for the first time that the novel 5-HT(3) subunits are able to form heteromeric 5-HT(3) receptors, which exhibit quantitatively different functional properties compared with homomeric 5-HT(3A) receptors.

[Novel therapeutic approaches in the treatment of irritable bowel syndrome]

The treatment of irritable bowel syndrome due to the heterogeneous clinical symptoms and coexisting psychiatric disorders is still controversial. Although several agents with different mechanisms of action are widely used in clinical practice, there are only few drugs available with strong evidence of their efficacy, safety and tolerability at present. The etiology of irritable bowel syndrome is considered to be multifactorial: experimental and clinical research on visceral hypersensitivity, motility and brain-gut axis involving its neurotransmitters and receptors created the foundation of novel therapeutic approaches. Albeit nowadays several drugs (alosetron, tegaserod) have been registered in a few countries for the treatment of irritable bowel syndrome, further large clinical trials are required related to the new chemical entities.

Tales from the crypts: regulatory peptides and cytokines in gastrointestinal homeostasis and disease

The gastrointestinal (GI) tract is composed of a diverse set of organs that together receive extracorporeal nutrition and convert it to energy substrates and cellular building blocks. In the process, it must sort through all that we ingest and discriminate what is useable from what is not, and having done that, it discards what is "junk." To accomplish these many and varied tasks, the GI tract relies on endogenous enteric hormones produced by enteroendocrine cells and the enteric nervous system. In many instances, the mediators of these tasks are small peptides that home to the CNS and accessory gut organs to coordinate oral intake with digestive secretions. As the contents of ingested material can contain harmful agents, the gut is armed with an extensive immune system. A breach of the epithelial barrier of the GI tract can result in local and eventually systemic disease if the gut does not mount an aggressive immune response.