Irritable bowel syndrome: update on pathogenesis and management

Physiology, signaling, and pharmacology of opioid receptors and their ligands in the gastrointestinal tract: current concepts and future perspectives

Opioid receptors are widely distributed in the human body and are crucially involved in numerous physiological processes. These include pain signaling in the central and the peripheral nervous system, reproduction, growth, respiration, and immunological response. Opioid receptors additionally play a major role in the gastrointestinal (GI) tract in physiological and pathophysiological conditions. This review discusses the physiology and pharmacology of the opioid system in the GI tract. We additionally focus on GI disorders and malfunctions, where pathophysiology involves the endogenous opioid system, such as opioid-induced bowel dysfunction, opioid-induced constipation or abdominal pain. Based on recent reports in the field of pharmacology and medicinal chemistry, we will also discuss the opportunities of targeting the opioid system, suggesting future treatment options for functional disorders and inflammatory states of the GI tract.

Antinociceptive effect of VSL#3 on visceral hypersensitivity in a rat model of irritable bowel syndrome: a possible action through nitric oxide pathway and enhance barrier function

Irritable bowel syndrome (IBS) is a functional bowel disorder characterized by visceral hypersensitivity and altered bowel function. There are increasing evidences suggested that VSL#3 probiotics therapy has been recognized as an effective method to relieve IBS-induced symptoms. The aim of this study was to examine the effects of VSL#3 probiotics on visceral hypersensitivity (VH), nitric oxide (NO), fecal character, colonic epithelium permeability, and tight junction protein expression. IBS model was induced by intracolonic instillation of 4% acetic acid and restraint stress in rats. After subsidence of inflammation on the seventh experimental day, the rats were subjected to rectal distension, and then the abdominal withdrawal reflex and the number of fecal output were measured, respectively. Also, colonic permeability to Evans blue was measured in vivo, and tight junction protein expression was studied by immunohistochemistry and immunoblotting method. Rats had been pretreated with VSL#3 or aminoguanidine (NOS inhibitor) or VSL#3+ aminoguanidine before measurements. The rats at placebo group showed hypersensitive response to rectal distension (P < 0.05) and defecated more stools than control rats (P < 0.05), whereas VSL#3 treatment significantly attenuated VH and effectively reduced defecation. Aminoguanidine reduced the protective effects of VSL#3 on VH. A pronounced increase in epithelial permeability and decreased expression of tight junction proteins (occludin, ZO-1) in placebo group were prevented by VSL#3, but not aminoguanidine. VSL#3 treatment reduce the hypersensitivity, defecation, colonic permeability and increase the expression of tight junction proteins (occludin, ZO-1). As the part of this effect was lowered by NOS inhibitor, NO might play a role in the protective effect of VSL#3 to some extent.

Women with irritable bowel syndrome and their perception of a good quality of life

Irritable bowel syndrome has a negative impact on a person's quality of life, but only a few existing studies have been based on patients' own perceptions. This study therefore aimed to collect information on the view of female patients with irritable bowel syndrome regarding what constitutes a good quality of life for them and to create a healthcare model for these patients. For the study, 30 women with irritable bowel syndrome (median age, 38.5 years; range, 20-65 years) responded in writing to a single, all-inclusive question: "What is your perception of a good quality of life?" When the questionnaires were returned, there was time for a short dialogue, and notes of the conversations were made. Data were analyzed qualitatively according to Burnard's method of thematic content analysis. The answers also were counted and thereby quantified. The women's perception of a good quality of life could be divided into five categories: (a) physical and mental health, (b) social well-being, (c) welfare, (d) strength and energy, and (e) self-fulfillment. According to the results, a healthcare model for patients with irritable bowel syndrome should include four main areas: (a) treatment of the patient's symptoms, (b) confirmation of the patient, (c) confirmation of the diagnosis, and (d) instruction for the patient. The healthcare model should be focused on the primary care level and should include a longitudinal plan of healthcare that also describes the secondary care level.

A comparison of the pharmacological properties of guinea-pig and human recombinant 5-HT4 receptors

BACKGROUND AND PURPOSE

5-HT(4) receptor agonists are used therapeutically to treat disorders of reduced gastrointestinal motility. Since such compounds are evaluated in guinea-pigs, we cloned, expressed and pharmacologically characterized the guinea-pig 5-HT(4) and human 5-HT(4(b)) splice variant, which share 95% homology. The functional properties of guinea-pig 5-HT(4(b)) receptors were compared with native receptors in guinea-pig colon.

EXPERIMENTAL APPROACH

Membrane radioligand binding and whole cell cAMP accumulation assays were used to determine the affinities, potencies and intrinsic activities (IA). Contraction of the guinea-pig distal colon longitudinal muscle myenteric plexus preparation (LMMP) was monitored to evaluate functional activity.

KEY RESULTS

pK(i) values for guinea-pig and human recombinant receptors, and guinea-pig striatum 5-HT(4) receptors, were in agreement, as were the potency and IA values for guinea-pig and human 5-HT(4) receptors expressed at a similar density ( approximately 0.2 pmol mg(-1) protein). Tegaserod was a potent (pEC(50)=8.4 and 8.7, respectively), full agonist at both guinea-pig and human 5-HT(4) receptors. In contrast, in the LMMP preparation, tegaserod was a potent, partial agonist (pEC(50)=8.2; IA=66%).

CONCLUSIONS AND IMPLICATIONS

Close agreement between the pharmacological properties of guinea-pig and human 5-HT(4) receptors support the use of guinea-pig model systems for the identification of 5-HT(4) receptor therapeutics. However, the mechanisms underlying the different agonist properties of tegaserod in recombinant and isolated tissue preparations, and the extent to which these impact the clinical efficacy of tegaserod as a prokinetic agent, remain to be determined.

Costs of irritable bowel syndrome in the UK and US

Irritable bowel syndrome (IBS) is one of the most common functional gastrointestinal disorders, with an estimated prevalence rate in the general population of 10-15% in industrialised countries. Although IBS is not a life-threatening disease, it contributes significantly to a large segment of healthcare resource consumption. This review provides an overview of studies addressing the direct and indirect costs of IBS in the US and the UK. A systematic literature search was conducted in MEDLINE and the Cochrane library; additionally, all reference lists covering the years from 1960 to May 2004 were scanned. Twenty-four publications for the US and the UK, published between 1991 and 2003, were identified: 6 were excluded, 18 were included. Data for the UK, US and UK + US were reported in 5, 11 and 2 publications, respectively. Total direct cost estimates per patient per year ranged from US 348 dollars to US 8750 dollars (calculated for year 2002). The average number of days off work per year because of IBS was between 8.5 and 21.6; indirect costs ranged from US 355 dollars to US 3344 dollars. The total costs and cost components of IBS are influenced by several factors: features of the investigated patient group (age, limitation to healthcare seekers or all IBS patients, comorbidity, severity of symptoms), database used, method of data collection (retrospective or prospective, varying cost components, time-point of data collection in relation to index-date of IBS diagnosis, method of cost calculation [incidence or prevalence based]) and different healthcare systems in the US and the UK. These factors led to the incomparability of published data, thus no comprehensive picture can be drawn of the total costs related to IBS in the UK and US. Data underline the magnitude of the economic impact of IBS in the UK and US, which is increased by a factor of 1.1-6.0, compared with matched non-IBS control groups. IBS contributes both direct and indirect costs to the total healthcare bill. Further studies should take influencial factors into account and report related data carefully in order to provide useful and comparable published cost data. Additionally, further research on the cost effectiveness of diagnostic procedures and therapies in IBS is required to define strategies to help IBS patients improve their quality of life and reduce related costs.

Recognizing and managing patients with irritable bowel syndrome

PURPOSE

To address the diagnosis and clinical management of irritable bowel syndrome (IBS) and provide a discussion of the available serotonergic agents.

DATA SOURCES

Recent studies examining the pathophysiology of IBS.

CONCLUSIONS

Diagnostic testing may be required in the subset of patients with IBS who present with alarm symptoms, or "red flags," suggestive of underlying organic disease. An important role has been suggested for the neurotransmitter serotonin in both gut motility and visceral pain sensitivity.

IMPLICATIONS FOR PRACTICE

A diagnosis of IBS is largely based on symptoms; therefore, effective clinician-patient communication and careful attention to details of patient presentation, history, and physical examination are essential.

Psychological well-being and symptoms in women with chronic constipation treated with sodium picosulphate

The use of sodium picosulphate has been restricted to a few weeks due to its potentially harmful effect on the colon. In spite of this restriction, however, many patients prefer this pharmaceutical drug. The authors have earlier studied the use of sodium picosulphate and found regular use leads to a moderate dose escalation. The aim of this study was to examine whether subjects who use laxatives containing sodium picosulphate differ in their psychological well-being and symptoms from subjects who use other laxatives, and to decide, on the basis of the results, how to use drugs containing sodium picosulphate. Eighty-six women, age 27-65 years, with chronic constipation were interviewed by two self-administered questionnaires: the Psychological General Well-Being Index (PGWB) and the Gastrointestinal Symptom Rating Scale (GSRS). Twenty-two of the subjects were interviewed a second time some months later after inclusion in a drug trial. Thirty-five women used sodium picosulphate regularly every week and 51 used other laxatives. Psychological well-being according to the PGWB was better for the subjects who used sodium picosulphate regularly than for those who used other laxatives (97 compared to 86, p, .017) This difference was due to less anxiety (p, .0001). There was no difference between the groups according to the GSRS. After inclusion in a drug trial, but before the introduction of the drugs, the group who did not use sodium picosulphate was remarkably improved with less anxiety, better self-control, and reduced abdominal pain and constipation. As the psychological well-being was better for the subjects who used sodium picosulphate, these drugs can be used when patients fail to respond to traditional therapies.

Update in the pharmaceutical therapy of the irritable bowel syndrome

The therapeutic management of the irritable bowel syndrome (IBS) is ineffective and not satisfying either patients or practitioners. Research in functions of the enteric nervous system and its interaction with the central nervous system is the basis for the development of emerging pharmaceuticals in therapy of the IBS. These pharmaceuticals include agents such as opioid agonists, psychotropic agents and particularly serotonin receptor modulators. These novel pharmaceuticals aim to provide a more comprehensive approach in the therapy of the IBS and will serve both patients and practitioners. So far, the US Food and Drug Administration has approved two agents specifically for the treatment of the IBS, both belonging to the group of serotonin receptor modulators. However, questions remain whether a single therapy is sufficient in the management of IBS because this disease is influenced by biological and psychological as well as cultural and social factors.

Irritable bowel syndrome in women: a common health problem

Irritable bowel syndrome is a common but complex problem that disproportionately affects women. Nurses are ideally situated to provide accurate information regarding the disorder and to provide symptom management. Currently, the diagnosis is based on the presence of abdominal pain and alterations in bowel habits. A multicomponent approach beginning with education and reassurance is more likely to be effective than one focused on a predominant symptoms (eg., constipation) alone. Building a therapeutic relationship with the patient over time will likely enhance the effectiveness of the prescribed therapy. Treatment paradigms that include new drugs that affect more than one symptom of IBS, along with nondrug therapies (eg, relaxation and cognitive behavioral strategies), will likely hold the greatest promise for management.

Effect of enterokinetic prucalopride on intestinal motility in fast rats

AIM: To evaluate the effects of prucalopride on intestinal prokinetic activity in fast rats and to provide experimental basis for clinical treatment of gastrointestinal motility diseases.

METHODS: Gastrointestinal propulsion rate was measured by the migration rate of activated charcoal, which reflexes gastrointestinal motility function. 120 Spraque-Dawley rats were randomly divided into four groups and received an intravenous injection of physiological saline (served as control), prucalopride 1 mg/kg, prucalopride 2 mg/kg and cisapride 1 mg/kg, respectively. The gastrointestinal propulsion rate was measured 1, 2 or 4 h after intravenous injection of the drugs.

RESULTS: Significant accelerations of gastrointestinal propulsion rate in prucalopride 1 mg/kg and 2 mg/kg groups were found compared with control group at 2 and 4 h (83.2% ± 5.5%, 81.7% ± 8.5% vs 70.5% ± 9.2%, P < 0.01; 91.2% ± 2.2%, 91.3% ± 3.9% vs 86.8% ± 2.6%, P < 0.01). The gastrointestinal propulsion rates at 1, 2 or 4 h were faster in prucalopride 1 mg/kg and 2 mg/kg groups than in cisapride group (84.0% ± 11.7%, 77.1% ± 11.9% vs 66.3% ± 13.6%, P < 0.01, P < 0.05; 83.2% ± 5.5%, 81.7% ± 8.5% vs 75.4% ± 5.9%, P < 0.01, P < 0.05; 91.2% ± 2.2%, 91.3% ± 3.9% vs 88.6% ± 3.5%, P < 0.05, P < 0.05). No difference of gastrointestinal propulsion rate was found between prucalopride 1 mg/kg group and prucalopride 2 mg/kg group (P > 0.05).

CONCLUSION: Prucalopride accelerates intestinal motility in fast rats, and has no dose dependent effect.

Chronic episodic disorders in women

Chronic episodic disorders, such as depressive disorders, IBS, migraine, and FMS, have important commonalities, including cormorbidities, an absence of classic anatomic pathology in the tissues, a lack of objective findings on physical examination, and a lack of abnormal findings by routine laboratory and radiologic tests. These CED are more prevalent in women (perhaps due to changes in estrogen levels), are generally worsened by stress (with resultant hyperactivity of the HPA axis), and often improve with aerobic exercise and common classes of medications affecting serotonin function, such as antidepressants. Thus, an increased understanding of the CED may result in improved treatment and functioning of many patients.