Cholecystokinin's role in regulation of colonic motility in health and in irritable bowel syndrome

Postprandial effect of gastrointestinal hormones and gastric activity in patients with irritable bowel syndrome

Altered gut regulation, including motor and secretory mechanisms, is characteristic of irritable bowel syndrome (IBS). The severity of postprandial symptoms in IBS patients is associated with discomfort and pain; gas-related symptoms such as bloating and abdominal distension; and abnormal colonic motility. The aim of this study was to assess the postprandial response, i.e., gut peptide secretion and gastric myoelectric activity, in patients with constipation-predominant IBS. The study was conducted on 42 IBS patients (14 males, 28 females, mean age 45.1 ± 15.3 years) and 42 healthy participants (16 males, 26 females, mean age 41.1 ± 8.7 years). The study assessed plasma gut peptide levels (gastrin, CCK-Cholecystokinin, VIP-Vasoactive Intestinal Peptide, ghrelin, insulin) and gastric myoelectric activity obtained from electrogastrography (EGG) in the preprandial and postprandial period (meal-oral nutritional supplement 300 kcal/300 ml). Mean preprandial gastrin and insulin levels were significantly elevated in IBS patients compared to the control group (gastrin: 72.27 ± 26.89 vs. 12.27 ± 4.91 pg/ml; p < 0.00001 and insulin: 15.31 ± 12.92 vs. 8.04 ± 3.21 IU/ml; p = 0.0001), while VIP and ghrelin levels were decreased in IBS patients (VIP: 6.69 ± 4.68 vs. 27.26 ± 21.51 ng/ml; p = 0.0001 and ghrelin: 176.01 ± 88.47 vs. 250.24 ± 84.55 pg/ml; p < 0.0001). A nonsignificant change in the CCK level was observed. IBS patients showed significant changes in postprandial hormone levels compared to the preprandial state-specifically, there were increases in gastrin (p = 0.000), CCK (p < 0.0001), VIP (p < 0.0001), ghrelin (p = 0.000) and insulin (p < 0.0001). Patients with IBS showed reduced preprandial and postprandial normogastria (59.8 ± 22.0 vs. 66.3 ± 20.2%) compared to control values (83.19 ± 16.7%; p < 0.0001 vs. 86.1 ± 9.4%; p < 0.0001). In response to the meal, we did not observe an increase in the percentage of normogastria or the average percentage slow-wave coupling (APSWC) in IBS patients. The postprandial to preprandial power ratio (PR) indicates alterations in gastric contractions; in controls, PR = 2.7, whereas in IBS patients, PR = 1.7, which was significantly lower (p = 0.00009). This ratio reflects a decrease in gastric contractility. Disturbances in the postprandial concentration of gut peptides (gastrin, insulin and ghrelin) in plasma may contribute to abnormal gastric function and consequently intestinal motility, which are manifested in the intensification of clinical symptoms, such as visceral hypersensitivity or irregular bowel movements in IBS patients.

Gastrocolonic Response

PURPOSE OF REVIEW

The gastrocolonic response (GCR), is a physiologic increase in motor activity of the colon, which usually occurs within minutes following meal ingestion. Over the years several triggers that provoke GCR were recognized including gastric dilation, caloric intake, and fat component of the meal. The response is mediated by the vagal nerve and neurohumoral mechanisms, and it can be modified by several pharmacological factors. Assessment of GCR is part of high-resolution colonic manometry studies, performed in patients with suspected colonic dysmotility. This review highlights the physiologic basis of GCR as well as its clinical and diagnostic features and implementation in variable pathological conditions and clinical practice.

RECENT FINDINGS

GCR has a role in patients with constipation, diabetes, dumping syndrome, bowel hyper and hypomotility and irritable bowel syndrome. Novel sensory triggers for GCR were recently recognized. GCR is a physiological response which is evaluated during colonic manometry studies. Abnormal GCR is a marker of an underlying pathology, which can provide a potential target for treatment.

Clinical, psychological, and physiological correlates of patients who defecate after meal

BACKGROUND AND AIMS

Food is the most important synchronizer of gastrointestinal motility and secretion. Many patients with functional bowel or anorectal disorders complain of fecal urge and stool output after eating.

PATIENTS AND METHODS

In this prospective observational study, 408 consecutive outpatients with functional bowel and/or anorectal disorders (74% female, 50.2±15.6 years, 24.8±5.0 kg/m²) filled Rome III questionnaires. Depression and anxiety scores, a physiological evaluation (total and segmental colonic transit time, colonic transit response to eating using a standard 1000 kcal test meal, and anorectal manometry), were measured. Univariate analysis and multivariate logistic regression were carried out according to the presence or not of stool output after eating.

RESULTS

Defecation after eating was found in 21% of patients. These patients were not different according to the demographic characteristics of sex ratio (P=0.702), age (P=0.830), and BMI (P=0.314). In contrast, they had lower state anxiety (P=0.032), but similar scores of depression (P=0.240) and trait anxiety (P=0.933). They had similar manometric characteristics (anal pressure and rectal sensitivity), but a greater response to eating in all segments of the colon. There was an increase in the frequency of functional diarrhea (odds ratio=2.576, 95% confidence interval=1.312-5.056; P=0.006) and levator ani syndrome (odds ratio=2.331, 95% confidence interval=1.099-4.944; P=0.017), but no other functional bowel disorder including irritable bowel syndrome and its subtypes was found.

CONCLUSION

Stool output after eating is associated with clinical disorders but not physiological parameters. This symptom is not associated with irritable bowel syndrome, but a higher frequency of functional diarrhea.

Cholecystokinin revisited: CCK and the hunger trap in anorexia nervosa

Objective

Despite a number of studies in the past decades, the role of Cholecystokinin (CCK) in anorexia nervosa (AN) has remained uncertain. In this study a highly specific assay for the biologically active part of CCK was used in patients with bulimic as well as with the restricting type of AN who were followed over the course of weight gain.

Methods

Ten patients with restricting and 13 with bulimic AN were investigated upon admission (T0), after a weight gain of at least 2 kg on two consecutive weighting dates (T1), and during the last week before discharge (T2) from inpatient treatment in a specialized clinic. Blood samples were drawn under fasting conditions and 20 and 60 minutes following a standard meal (250 kcal). Data were compared to those of eight controls matched for sex and age. Gastrointestinal complaints of patients were measured by a questionnaire at each of the follow-up time points.

Results

At admission, AN patients exhibited CCK-levels similar to controls both prior to and after a test meal. Pre and post-meal CCK levels increased significantly after an initial weight gain but decreased again with further weight improvement. CCK release was somewhat lower in bulimic than in restricting type AN but both subgroups showed a similar profile. There was no significant association of CCK release to either initial weight or BMI, or their changes, but CCK levels at admission predicted gastrointestinal symptom improvement during therapy.

Conclusions

Normal CCK profiles in AN at admission indicates hormonal responses adapted to low food intake while change of eating habits and weight gain results in initially increased CCK release (counteracting the attempts to alter eating behavior) that returns towards normal levels with continuous therapy.

Effect of cholecystokinin on rectal motor and sensory function in patients with irritable bowel syndrome and healthy controls

AIM

Ingestion of a meal frequently induces an urge to defaecate, the so-called gastro-colonic or gastro-rectal reflex. In patients with irritable bowel syndrome (IBS), symptoms are often provoked by meals. Cholecystokinin (CCK), a proximal gut peptide released after ingestion of a meal, may mediate these postprandial changes. The potential role of CCK in rectal sensory and motor function was evaluated by a rectal barostat study in healthy controls and patients with IBS. METHOD ; The sensory effects on serosal and mucosal receptors were studied. Twelve healthy controls and 12 patients with IBS underwent a ramp distension procedure of the rectum during infusion of CCK and placebo in random order. In 10 other healthy controls and 10 IBS patients an intermittent distension procedure was performed during infusion of CCK and placebo in random order.

RESULTS

No differences were found in rectal compliance during ramp distensions between IBS patients and controls. CCK did not affect perception of urge and pain in controls or in IBS patients. Similar results were obtained during the intermittent distensions, but at higher distension pressures CCK significantly increased rectal sensitivity in IBS patients.

CONCLUSION

Infusion of exogenous CCK to plasma levels normally seen in the postprandial state did not influence rectal motor function or sensations during ramp distension but it did significantly increase pain sensation in IBS patients during rapid intermittent distension.

Dietary triggers in irritable bowel syndrome

Irritable bowel syndrome (IBS) is a frequently occurring, benign functional gastrointestinal disorder with a complex poorly understood pathology which appears to be multifactorial in nature. There is no association with structural or biochemical abnormalities in the gastrointestinal tract. Functional variations in myoelectrical activity, visceral hypersensitivity and illness behaviours have all been observed in patients experimentally. In conjunction with environmental, psychological and alimentary factors, these mechanisms have been proposed as the major determinants of symptom genesis. Certainly, dietary factors are frequently perceived by sufferers as powerful symptom triggers, with many reporting multiple food intolerance. Physicians, however, remain divided upon the relevance of food to the disorder, with many eschewing a nutritional connection. This is unsurprising as, despite much experimental work to determine the clinical relevance of food intolerance and allergy to the aetiology of the disorder, the vast range of foodstuffs available for testing, inherent procedural problems with test foods, methodological insufficiencies and the continually evolving knowledge of the disorder, particularly the subgrouping of sufferers, have restricted the scientific validity of current findings. At the present time, it is difficult to make informed judgement upon the importance of food in IBS, and rigorously designed, large scale trials devised in the light of recent knowledge are required before conclusions can be drawn.

Heart rate variability in the irritable bowel syndrome: a review of the literature

BACKGROUND

Patients with irritable bowel syndrome (IBS) often present with disturbances of bowel habits (diarrhea, constipation) and abdominal pain/discomfort that are modulated by the autonomic nerve system (ANS). In this narrative review, we analyzed studies that measured ANS functioning in IBS by means of heart rate variability (HRV).

METHODS

The PUBMED was searched with the keywords 'irritable bowel syndrome' AND ('heart rate variability' OR 'autonomic function'). We included only papers that used 'traditional' HRV indices and diagnosed IBS based on Manning or Rome criteria. Studies were sub-grouped according to methodological features of HRV analysis (24-h monitoring, short-term laboratory records, records during sleep).

KEY RESULTS

Most studies reported no difference in HRV when the IBS population was compared to healthy controls. Dividing the IBS sample into subgroups--according to their predominant bowel symptoms, the severity of clinical course, the presence of depressive symptoms, or a history of abuse in the past--revealed changes in autonomic functioning.

CONCLUSIONS & INFERENCES

Patients with IBS appear to experience symptoms that may be the result of changes in ANS functioning. HRV measures in clinical routine may allow assessing these changes, but further studies performed in a standardized fashion should improve the validity of HRV measures for clinical research first.

Plasma hormones facilitated the hypermotility of the colon in a chronic stress rat model

Objective

To study the relationship between brain-gut peptides, gastrointestinal hormones and altered motility in a rat model of repetitive water avoidance stress (WAS), which mimics the irritable bowel syndrome (IBS).

Methods

Male Wistar rats were submitted daily to 1-h of water avoidance stress (WAS) or sham WAS (SWAS) for 10 consecutive days. Plasma hormones were determined using Enzyme Immunoassay Kits. Proximal colonic smooth muscle (PCSM) contractions were studied in an organ bath system. PCSM cells were isolated by enzymatic digestion and IKv and IBKca were recorded by the patch-clamp technique.

Results

The number of fecal pellets during 1 h of acute restraint stress and the plasma hormones levels of substance P (SP), thyrotropin-releasing hormone (TRH), motilin (MTL), and cholecystokinin (CCK) in WAS rats were significantly increased compared with SWAS rats, whereas vasoactive intestinal peptide (VIP), calcitonin gene-related peptide (CGRP) and corticotropin releasing hormone (CRH) in WAS rats were not significantly changed and peptide YY (PYY) in WAS rats was significantly decreased. Likewise, the amplitudes of spontaneous contractions of PCSM in WAS rats were significantly increased comparing with SWAS rats. The plasma of WAS rats (100 µl) decreased the amplitude of spontaneous contractions of controls. The IKv and IBKCa of PCSMs were significantly decreased in WAS rats compared with SWAS rats and the plasma of WAS rats (100 µl) increased the amplitude of IKv and IBKCa in normal rats.

Conclusion

These results suggest that WAS leads to changes of plasma hormones levels and to disordered myogenic colonic motility in the short term, but that the colon rapidly establishes a new equilibrium to maintain the normal baseline functioning.

Food: the forgotten factor in the irritable bowel syndrome

After years of inattention, there is a growing body of evidence to suggest that dietary constituents at least exacerbate symptoms and perhaps contribute to the pathogenesis of the irritable bowel syndrome (IBS). Although patients with IBS self-report food allergies more often than the general population, the evidence suggests that true food allergies are relatively uncommon. Less clearly defined food intolerances may be an important contributor to symptoms in IBS patients. This article reviews the literature supporting a causal link between food and the symptoms of IBS as well as the evidence supporting dietary interventions as a means of managing IBS symptoms.

Investigational agents for the irritable bowel syndrome

IMPORTANCE OF THE FIELD

Irritable bowel syndrome (IBS) is a common disorder with significant health and economic consequences. The etiology of IBS is complex and appears to be multifactorial. Traditional IBS therapies have been directed primarily at the relief of individual symptoms but have been largely disappointing. This has triggered the search for newer treatment strategies with improved patient outcomes.

AREAS COVERED IN THIS REVIEW

Enhanced knowledge about the putative pathophysiology of IBS has allowed the identification of new mechanistic targets for treatment. Our aim is to review emerging and promising drugs in the treatment of IBS based on disease pathophysiology. Data were extracted using Medline and PubMed search engines until January 2010. Abstracts were identified through 'Web of Science' and abstract supplements of major gastrointestinal scientific meetings. Drugs were classified according to mechanism of action and those with efficacy in trials involving human subjects examined.

WHAT THE READER WILL GAIN

Additional insight into the pathophysiology as well as current and prospective treatments of IBS.

TAKE HOME MESSAGE

A multitude of putative drug targets have been identified and some novel treatments have progressed through to human clinical trials, but very few will be approved for the market in the near future. Moreover, and in keeping with the complex and multifactorial nature of this syndrome, it is unlikely that there will be one dominant and universally effective form of therapy for all IBS patients.

Evolution of the restorative proctocolectomy and its effects on gastrointestinal hormones

Gastrointestinal (GI) peptide hormones are chemical messengers that regulate secretory, mechanical, metabolic, and trophic functions of the gut. Restorative proctocolectomy (RPC) or resection of the colon and rectum with maintenance of intestinal continuity through the construction of an ileal pouch reservoir and preservation of the anal sphincters has become the standard of care for the surgical treatment of ulcerative colitis and familial adenomatous polyposis. The manipulation of the digestive system to create the ileal pouch involves altering gut-associated lymphoid tissue among other anatomic changes that lead to changes in GI peptides. In addition, the ileal pouch epithelium responds to a wide variety of stimuli by adjusting its cellularity and function. These adaptive mechanisms involve systemic factors, such as humoral and neural stimuli, as well as local factors, such as changes in intestinal peristalsis and intraluminal nutrients. There have been conflicting reports as to whether the alterations in GI hormones after RPC have actual clinical implications. What the studies on alterations of GI peptides' response and behavior after RPC have contributed, however, is a window into the possible etiology of complications after pouch surgery, such as pouchitis and malabsorption. Given the possibility of pharmacologically modifying GI peptides or select components of adaptation as a therapeutic strategy for patients with ileal pouch dysfunction or pouchitis, a clear understanding of human pouch mucosal adaptation is of paramount importance. In this review, we summarize the evolution of the RPC and its effects on the GI hormones as well as their possible clinical implications.

Regional differences in the effects of various doses of cerulein upon the small-intestinal migrating motor complex in fasted and non-fasted sheep

There are no precise data concerning the effect of cerulein on the small-intestinal migrating motor complex (MMC) in sheep. Thus, the effort was directed towards the elucidation of the role of cerulein, a cholecystokinin (CCK) amphibian analogue, in the regulation of MMC cycle in conscious fasted and non-fasted sheep in various regions of the small intestine. In six sheep, equipped with bipolar electrodes in the entire small intestine and with one duodenal strain gauge force transducer in four of these animals, the continuous myoelectric and motor activity recordings were performed. During control period, two normal consecutive MMC cycles were recorded in fasted and non-fasted animals and then cerulein was slowly injected at the dose 1 (during 30 s), 10 (during 30 s or 60 s) or 100 ng/kg (during 30 s, 60 s or 120 s) or infused at the dose 0.5 or 1.5 ng/kg/min during 60 min. After cerulein administration at least two consecutive MMC cycles were also recorded. It was found that cerulein in moderate and higher doses injected in both fasted and non-fasted animals, especially during phase 2a or 2b MMC, inhibited phase 3 in the duodenum in at least one-third of the experiments and significantly increased the MMC cycle duration. The application of 100 ng/kg of cerulein during 120 s in the course of phase 2b MMC prolonged cycle duration from 70 +/- 21 to 113 +/- 19 min (p < 0.05) or from 51 +/- 18 to 113 +/- 19 min (p < 0.01) in fasted and non-fasted sheep respectively. The first phase 3 MMC arriving after cerulein administration at the highest dose was usually abnormal in approximately 60% of the experiments. The second phase 3 observed following the hormone injection was abnormal much less frequently and to the lesser extent. Furthermore, both cerulein doses significantly shortened the duration of phase 3 MMC either in fasted (from approximately 5.5-6.5 cpm to 4-5 cpm) or in non-fasted sheep (from approximately 4.5-5.5 to 3-4.5 cpm). The effects of cerulein exhibited the dose-response character. They were more pronounced when cerulein was injected during phase 2b or 2a MMC when compared with phase 1 MMC. The effects of cerulein on the ileal MMC were less evident, although the inhibition of the ileal phase 3 in response to both higher injected doses was observed occasionally. Infusions of cerulein in non-fasted sheep exerted similar effects as cerulein injections. It was stated that cerulein exerts marked regulatory effect upon the small-intestinal MMC in sheep. Although it remains uncertain whether the efficient doses of cerulein used in the present study correspond to physiological or pharmacological doses of CCK it seems likely that most of these doses were physiological. Thus, it is concluded that cerulein participates in the control of MMC cycles in the digestive and interdigestive states in sheep. It is possible that CCK is a physiological regulator of the ovine small-intestinal MMC.

Role of CCK/gastrin receptors in gastrointestinal/metabolic diseases and results of human studies using gastrin/CCK receptor agonists/antagonists in these diseases

In this paper, the established and possible roles of CCK1 and CCK2 receptors in gastrointestinal (GI) and metabolic diseases are reviewed and available results from human agonist/antagonist studies are discussed. While there is evidence for the involvement of CCK1R in numerous diseases including pancreatic disorders, motility disorders, tumor growth, regulation of satiety and a number of CCK-deficient states, the role of CCK1R in these conditions is not clearly defined. There are encouraging data from several clinical studies of CCK1R antagonists in some of these conditions, but their role as therapeutic agents remains unclear. The role of CCK2R in physiological (atrophic gastritis, pernicious anemia) and pathological (Zollinger-Ellison syndrome) hypergastrinemic states, its effects on the gastric mucosa (ECL cell hyperplasia, carcinoids, parietal cell mass) and its role in acid-peptic disorders are clearly defined. Furthermore, recent studies point to a possible role for CCK2R in a number of GI malignancies. Current data from human studies of CCK2R antagonists are presented and their potential role in the treatment of these conditions reviewed. Furthermore, the role of CCK2 receptors as targets for medical imaging is discussed.

Proximal and distal gut hormone secretion in irritable bowel syndrome

OBJECTIVE

Sensory and motor dysfunctions of the gut are both important characteristics of irritable bowel syndrome (IBS). Several gut peptides contribute to the regulation of gastrointestinal function but little is known about gut hormone secretion in IBS.

MATERIAL AND METHODS

We evaluated perceptual thresholds and fasting and postprandial plasma levels of proximal (cholecystokinin (CCK), motilin) and distal (peptide YY) gut peptides up to 1 h after ingestion of a high caloric meal in 99 IBS patients and 40 age- and gender-matched healthy controls.

RESULTS

Fasting plasma CCK levels were significantly elevated in patients (1.2+/-0.8 pM) compared with those in controls (0.8+/-0.7 pM, p=0.006), as was the incremental postprandial CCK response (72+/-73 versus 40+/-42 pM.60 min, respectively; p=0.003). No differences in fasting and postprandial motilin or PYY levels were found. The postprandial PYY response was significantly increased in hypersensitive compared to normosensitive patients (215+/-135 versus 162+/-169 pM, p=0.048). Patients with a diarrhoea predominant bowel habit had higher fasting motilin levels compared to constipated patients or alternating type IBS patients (82.1+/-36.5 versus 60.8+/-25.1 versus 57.5+/-23.9 pM, one-way ANOVA p=0.003).

CONCLUSIONS

IBS patients have increased fasting and postprandial plasma levels of CCK. Changes in plasma levels of motilin and PYY may contribute to the clinical expression of IBS, such as the presence of visceral hypersensitivity or a predominant bowel habit.

CCK1 antagonists: are they ready for clinical use?

Cholecystokinin (CCK) is a peptide hormone which is found both in the gastrointestinal tract throughout the human small intestine and nerves in the myenteric plexus of the enteric nervous system and in the central nervous system. This dual location constitutes the anatomical basis for this in functions as a hormone and a neurotransmitter implicated in the regulation of both systems. CCK regulates not only motor functions in the gastrointestinal tract like lower oesophageal sphincter relaxation, gastric secretion and emptying, gall bladder contractility and bile secretion into the duodenum, intestinal and colonic motility, but also sensory functions and plays a role in the regulation of food intake. These effects are mediated through selective receptors CCK1 and CCK2. Over the last few years, research has focused on understanding the role of CCK, its receptors with antagonists at the biological, pharmacological, clinical and therapeutic level. As far as the CCK1 antagonists is concerned, important inroads have been made in the potential role of these antagonists in the treatment of GERD, IBS and pancreatitis. They have also shown encouraging results in sphincter of Oddi dysfunction and some gastrointestinal cancers. This review focuses on the recent ad vances of the biological role of CCK and their CCK1 antagonists: their current basic and clinical status in gastroenterology, with particular emphasis on the potential therapeutic role of the CCK1 antagonists and future research directions.

Proglumide attenuates experimental colitis in rats

Ulcerative colitis is associated with altered contractile activity and transit time of colon. On the other hand, cholecystokinin (CCK) has been shown to play an important role in regulation of gastrointestinal motor function including colonic contraction and transit. In the present study, an attempt was made to study the effect of proglumide, a CCK receptor antagonist on experimental colitis in rats. Experimental colitis was induced in male Sprague-Dawley rats by instilling 1 ml of 4% acetic acid followed by flushing with 0.5 ml air. The rats were kept in a head-down position for 30s. Finally, each rat received 1.5 ml colonic wash with 1.5 ml saline. Four groups of rats received proglumide orally (0, 250, 500 and 1000mg/kg). The first dose of proglumide was given 1 h before acetic acid challenge, whereas the second dose of proglumide was given 25 h after the first dose. Sham control rats received an equal volume of saline instead of acetic acid. Forty-eight hours after the acetic acid challenge, the colon was removed, weighed and split longitudinally and scored for injury. Part of the colon was used for histopathological study as well as analysis of myeloperoxidase (MPO) activity (as a marker of neutrophil activity). Acetic acid produced severe diarrhea and exfoliation of the colonic epithelium accompanied by extensive destruction of the mucosal interstitium. Proglumide dose dependently protected rats against acetic acid-induced increase in colon weight, diarrhea, MPO activity and colonic injury. Inhibition of CCK exerts a beneficial effect in experimental colitis. Further studies are warranted to determine the mechanism of protection and the therapeutic potential of CCK inhibitors.

Cholecystokinin-A receptor antagonists: therapies for gastrointestinal disorders

Cholecystokinin (CCK) is a peptide that exerts several regulatory functions in the periphery, as well as in the brain. The biological functions attributed to CCK are mediated by two receptor subtypes, termed CCKA and CCKB, located predominantly in the gastrointestinal (GI) tract and in the brain, respectively. Several selective and potent non-petide CCKA receptor antagonists have been synthesised and fully characterised in preclinical studies. A few of them have been, and continue to be tested in humans. This paper focuses on the data available on the effect of CCKA receptor antagonist administration in humans, and shows how, in addition to allowing a more exact definition of the role of CCK in the regulation of some GI functions, these drugs may also possess therapeutic potential in GI disorders.

Effect of CCK-1 antagonist, dexloxiglumide, in female patients with irritable bowel syndrome: a pharmacodynamic and pharmacogenomic study

BACKGROUND

Cholecystokinin (CCK) is involved in gastrointestinal motor response to meals. The potential role of CCK receptor antagonists in functional gastrointestinal disorders is unclear.

AIMS

To evaluate the effects of dexloxiglumide, a CCK-1 receptor antagonist, on gastrointestinal transit (GIT) and symptoms in patients with constipation-predominant IBS (C-IBS); and to explore the influence of CCK-1 receptor polymorphisms on gut transit and the pharmacodynamic response to therapy.

METHODS

A total of 36 patients with C-IBS and normal to slow baseline colonic transit (CT) were randomized (double-blind, parallel design) to 7 days of dexloxiglumide 200 mg or placebo t.i.d. Daily bowel habits diaries and weekly relief of IBS symptoms were recorded. At the end of treatment, GIT and CT were measured. Peripheral blood DNA was examined for polymorphisms in genes controlling CCK: four related to CCK-1, one to the CCK gene promoter, and one related to CCK-2. The distributions of allelic variants and association with gastric emptying in response to dexloxiglumide and placebo were assessed.

RESULTS

Dexloxiglumide was associated with accelerated gastric emptying t(1/2) (p= 0.004), and slower ascending colon emptying t(1/2) (p < 0.01), with no significant effect on overall CT or satisfactory relief of IBS. There was an association between CCK 779T > C polymorphism and slower rate of gastric emptying (p= 0.04).

CONCLUSIONS

Dexloxiglumide accelerates gastric emptying and delays proximal but not overall CT in patients with C-IBS. Dexloxiglumide does not accelerate transit in C-IBS. The role of CCK-1 gene polymorphisms in delaying gastric emptying and in determining response to therapy deserves further study.

Involvement of endogenous CCK and CCK1 receptors in colonic motor function

Cholecystokinin (CCK) is a brain-gut peptide; it functions both as a neuropeptide and as a gut hormone. Although the pancreas and the gallbladder were long thought to be the principal peripheral targets of CCK, CCK receptors are found throughout the gut. It is likely that CCK has a physiological role not only in the stimulation of pancreatic and biliary secretions but also in the regulation of gastrointestinal motility. The motor effects of CCK include postprandial inhibition of gastric emptying and inhibition of colonic transit. It is now evident that at least two different receptors, CCK(1) and CCK(2) (formerly CCK-A and CCK-B, respectively), mediate the actions of CCK. Both localization and functional studies suggest that the motor effects of CCK are mediated by CCK(1) receptors in humans. Since CCK is involved in sensory and motor responses to distension in the intestinal tract, it may contribute to the symptoms of constipation, bloating and abdominal pain that are often characteristic of functional gastrointestinal disorders in general and irritable bowel syndrome (IBS), in particular. CCK(1) receptor antagonists are therefore currently under development for the treatment of constipation-predominant IBS. Clinical studies suggest that CCK(1) receptor antagonists are effective facilitators of gastric emptying and inhibitors of gallbladder contraction and can accelerate colonic transit time in healthy volunteers and patients with IBS. These drugs are therefore potentially of great value in the treatment of motility disorders such as constipation and constipation-predominant IBS.

Involvement of endogenous CCK and CCK1 receptors in colonic motor function

Cholecystokinin (CCK) is a brain-gut peptide; it functions both as a neuropeptide and as a gut hormone. Although the pancreas and the gallbladder were long thought to be the principal peripheral targets of CCK, CCK receptors are found throughout the gut. It is likely that CCK has a physiological role not only in the stimulation of pancreatic and biliary secretions but also in the regulation of gastrointestinal motility. The motor effects of CCK include postprandial inhibition of gastric emptying and inhibition of colonic transit. It is now evident that at least two different receptors, CCK(1) and CCK(2) (formerly CCK-A and CCK-B, respectively), mediate the actions of CCK. Both localization and functional studies suggest that the motor effects of CCK are mediated by CCK(1) receptors in humans. Since CCK is involved in sensory and motor responses to distension in the intestinal tract, it may contribute to the symptoms of constipation, bloating and abdominal pain that are often characteristic of functional gastrointestinal disorders in general and irritable bowel syndrome (IBS), in particular. CCK(1) receptor antagonists are therefore currently under development for the treatment of constipation-predominant IBS. Clinical studies suggest that CCK(1) receptor antagonists are effective facilitators of gastric emptying and inhibitors of gallbladder contraction and can accelerate colonic transit time in healthy volunteers and patients with IBS. These drugs are therefore potentially of great value in the treatment of motility disorders such as constipation and constipation-predominant IBS.

Postoperative colonic motility increases after early food intake in patients undergoing colorectal surgery

BACKGROUND

Stimulation of colonic motility by the gastrocolonic response may help to reduce inhibition of gastrointestinal motility after colorectal surgery. We aimed to investigate whether postoperative colonic motility is increased after early food intake.

METHODS

Nineteen patients undergoing colorectal surgery and 7 healthy volunteers were investigated. Colonic motility was recorded with a combined manometry/barostat system, and the effect of a standard 500-kcal meal was evaluated once in healthy volunteers and in 15 patients on the first and second postoperative day. Four patients remained unfed, serving as controls.

RESULTS

In patients, the colonic motility index increased from 12 +/- 5 at baseline to 65 +/- 24 mm Hg after the meal on postoperative day 1 (mean +/- SEM; P < .01), while barostat bag volumes decreased, indicating a rise in colonic tone. On day 2, the motility index was 62 +/- 17 mm Hg at baseline and did not change after the meal. In unfed controls, no change was observed during colonic motility recordings on both postoperative days. In healthy volunteers, the colonic motility index increased from 98 +/- 52 at baseline to 151 +/- 58 mm Hg postprandially (P < .05).

CONCLUSIONS

As in healthy volunteers, there is a potential to stimulate colonic motility by early food intake in postoperative patients. This may help to improve prolonged colonic motility disorders after colorectal surgery.

Review article: the overlap between functional dyspepsia and irritable bowel syndrome -- a tale of one or two disorders?

Functional dyspepsia and irritable bowel syndrome are currently considered to be two separate nosological entities. However, the overlap of symptoms and the evidence of a number of common pathophysiological characteristics suggest that functional dyspepsia and irritable bowel syndrome may be different presentations of the same disorder. In this review, we critically appraise points in common, as well as differences, in the epidemiology, pathophysiology and response to treatment of functional dyspepsia and irritable bowel syndrome. Population-based studies and large case series show that one- to two-thirds of subjects with irritable bowel syndrome have symptoms that overlap with functional dyspepsia. Symptom analyses have generally failed to support functional dyspepsia and irritable bowel syndrome as separate entities. An exaggerated motor response to meals, delayed gastric emptying and abnormal small bowel and colonic transit can all be found in subsets of functional dyspepsia and irritable bowel syndrome, and are not exclusive to either condition. Visceral hypersensitivity is a common feature to both entities and seems unlikely to be site or disease specific. There is good evidence for the post-infectious development of irritable bowel syndrome, and this may also apply in functional dyspepsia. Psychiatric comorbidities are similar in functional dyspepsia and irritable bowel syndrome. Several common drug classes (prokinetics, visceral analgesics, psychoactive agents) may similarly improve both functional dyspepsia and irritable bowel syndrome symptoms. The evidence available suggests that at least subsets of functional dyspepsia and irritable bowel syndrome represent different manifestations of a single entity. The identification of common pathophysiological targets for therapy should be pursued in future research.

Oxytocin and cholecystokinin secretion in women with colectomy

Background

Cholecystokinin (CCK) concentrations in plasma have been shown to be significantly higher in colectomised subjects compared to healthy controls. This has been ascribed to reduced inhibition of CCK release from colon. In an earlier study CCK in all but one woman who was colectomised, induced release of oxytocin, a peptide present throughout the gastrointestinal (GI) tract. The aim of this study was thus to examine if colectomised women had a different oxytocin response to CCK compared to healthy controls.

Methods

Eleven women, mean age 34.4 ± 2.3 years, who had undergone colectomy because of ulcerative colitis or constipation were studied. Eleven age-matched healthy women served as controls. All subjects were fasted overnight and given 0.2 μg/kg body weight of CCK-8 i.v. in the morning. Samples were taken ten minutes and immediately before the injection, and 10, 20, 30, 45, 60, 90 and 120 min afterwards. Plasma was collected for measurement of CCK and oxytocin concentrations.

Results

The basal oxytocin and CCK concentrations in plasma were similar in the two groups. Intravenous injection of CCK increased the release of oxytocin from 1.31 ± 0.12 and 1.64 ± 0.19 pmol/l to 2.82 ± 0.35 and 3.26 ± 0.50 pmol/l in controls and colectomised women, respectively (p < 0.001). Given the short half-life of CCK-8 in plasma, the increased concentration following injection could not be demonstrated in the controls. On the other hand, in colectomised women, an increase of CCK in plasma was observed for up to 20 minutes after the injection, concentrations increasing from 1.00 ± 0.21 to a maximum of 1.81 ± 0.26 pmol/l (p < 0.002).

Conclusion

CCK stimulates the release of oxytocin in women. There is no difference in plasma concentrations between colectomised and controls. However, colectomy seems to reduce the metabolic clearance of CCK. The hyperCCKemia in patients who had undergone colectomy is consequently not only dependent on CCK release, but may also depend on reduced clearance.

Alterations of sensori-motor functions of the digestive tract in the pathophysiology of irritable bowel syndrome

Pathophysiology of irritable bowel syndrome (IBS) is based upon multiple factors that have been organised in a comprehensive model centred around the brain-gut axis. The brain-gut axis encompasses nerve pathways linking the enteric and the central nervous systems and contains a large proportion of afferent fibres. Functionally and anatomically, visceral nerves are divided in to two categories: the parasympathetic pathways distributing to the upper gut through the vagi and to the hindgut, through the pelvic and pudendal nerves, and the sympathetic pathways, arising form the spinal cord and distributing to the midgut via the paravertebral ganglia. Several abnormalities of gut sensori-motor function have been described in patients with IBS. Abnormal motility patterns have been described at the intestinal and colonic levels. Changes in colonic motility are mainly related to bowel disturbances linked to IBS but do not correlate with pain. More recently, visceral hypersensitivity has been recognised as a main characteristic of patients with IBS. It is defined by an exaggerated perception of luminal distension of various segments of the gut and related to peripheral changes in the processing of visceral sensations as well as modulation of perception by centrally acting factors including mood and stress. Viscero-visceral reflexes link the two edges of the brain-gut axis and may account for the origin of symptoms in some pathological conditions. Recent advances in the understanding of the role of myenteric plexus allowed recognition of several neurotransmitters involved at the level of both the afferent and efferent pathways. Targeting the receptors of these neurotransmitters is a promising way for development of new treatments for IBS.

Cholecystokinin octapeptide increases rectal sensitivity to pain in healthy subjects

Hypersensitivity during rectal distension has been demonstrated in irritable bowel syndrome (IBS). Studies performed in animals and indirect data in humans suggest that cholecystokinin (CCK) could modulate visceral sensations. The aim of this study was to assess the effects of i.v. infused sulphated cholecystokinin octapeptide (CCK-OP) on rectal sensitivity in response to distension. In eight healthy subjects, rectal sensitivity and compliance were determined during a randomized double-blind study, with four sessions each separated by 7 days. Sensory thresholds and rectal compliance were assessed during slow-ramp (40 mL min-1) and rapid-phasic distensions (40 mL s-1, 5 mmHg stepwise, 1-min duration), and were compared before and during continuous infusion of either saline or CCK-OP at 5, or 20 or 40 ng kg-1 h-1. During rapid phasic distension but not during slow ramp distension, CCK-OP at 40 ng kg-1 h-1 produced a significant decrease in sensory thresholds compared with the basal period. Rectal compliance was not modified by any infusion. At pharmacological doses, CCK-OP decreases sensory thresholds during rapid phasic distension that may preferentially stimulate serosal mechanoreceptors, but has no effect on mucosal mechanoreceptors stimulated during slow ramp distensions. Modulation of rectal sensitivity by CCK could be implicated in the pathogenesis of the rectal hypersensitivity observed in IBS.

Exaggerated motility of the descending colon with repetitive distention of the sigmoid colon in patients with irritable bowel syndrome

BACKGROUND

Visceral hypersensitivity is one of the mechanisms of irritable bowel syndrome (IBS), but it does not explain the entire symptomatology, i.e., altered bowel habit with abdominal pain relieved by defecation. We tested our hypothesis that an abnormal link between luminal stimulation and mural response may have some role in the pathophysiology of IBS.

METHODS

Patients with IBS (n = 10, median 21 years old, 5 male patients, 5 female patients) and healthy control subjects (n = 10, median 21 years old, 5 men, 5 women) were studied. A manometric catheter with three transducers was inserted to the descending colon and a balloon was placed in the distal sigmoid colon. Another catheter with three transducers was inserted to the duodenum. After baseline for 30min, the sigmoid colon was stimulated by balloon distention for 30min followed by recovery for 30min. Balloon distention was repeated 100 times, and each stimulation consisted of a 5-s inflation and a 10-s deflation, with a volume of 50ml maximum. The sensory threshold of balloon inflation was then examined, and plasma adrenocorticotropic hormone (ACTH) was measured with radioimmunoassay.

RESULTS

Repetitive colonic distention induced a significant increase in motility indices (mmHg s/s%) of the descending colon in the IBS patients (from 118 +/- 25 to 333 +/- 108, P < 0.05) but not of those in controls (from 90 +/- 16 to 89 +/- 19). A significant group difference (P < 0.05), period effect (P < 0.02), and group x period interactions (P < 0.01) were detected with two-way ANOVA. Duodenal motility indices in controls were significantly reduced by colonic distention (from 169 +/- 25 to 104 +/- 14, P < 0.01), but those in the IBS patients were not (from 156 +/- 17 to 124 +/- 20). The sensory threshold of balloon inflation in the IBS patients (74 +/- 10ml) was significantly lower than that in controls (125 +/- 6ml, P < 0.001). There was no significant difference in plasma ACTH levels between the IBS patients and controls.

CONCLUSIONS

Repetitive distention of the distal sigmoid colon below the sensory threshold induced orad exaggerated motility of the colon in IBS patients. The distention inhibited motility of the small intestine in healthy subjects, but this inhibition was blunted in IBS patients. These results suggest that IBS patients may have not only visceral hypersensitivity, but also an abnormal intestinal reflex.

Effects of extrinsic autonomic denervation and myenteric plexus transection on colonic motility in conscious dogs

BACKGROUND

The role of extrinsic autonomic nerves in regulation of colonic contractile activity is not well understood.

METHODS

Twelve dogs had 6 strain gauge force transducers implanted in the colon and were divided into 3 experimental groups: (1) a control group, (2) an extrinsic denervation group (denervation group), and (3) an extrinsic denervation with proximal intrinsic myenteric plexus transection group (denervation + transection group). After recovery, colonic contractile activity during fasting and effects of feeding on gastrocolonic response were recorded.

RESULTS

Colonic contractile activity occurred not only in the denervation group but also in the denervation + transection group. Both mean duration and propagation time of the colonic contractile activity were shorter in the denervation + transection group than in the control group. In the denervation group, propagation time was shorter than in the controls but the other parameters were not different. Feeding failed to immediately induce the gastrocolonic response in both experimental groups.

CONCLUSIONS

We conclude that extrinsic nerves are not required for the appearance of colonic contractile activity. However, colonic contractile activity and its propagation are modulated by extrinsic innervation or proximal intrinsic neural continuity. Gastrocolonic response may be predominantly under extrinsic neural control.

Irritable bowel syndrome

Irritable bowel syndrome is a biopsychosocial disorder characterized by dysregulation of intestinal motor, sensory, and central nervous system functions. It is associated with significant disability and health-care costs. The traditional diagnostic approach leads to excessive investigation for many patients. A reductionist approach of focusing on evaluation and treatment of a single mechanism is unlikely to prove effective. Identification of the characteristic symptom pattern is the key to cost-effective management. A strong patient-physician relationship is essential for a successful outcome. Optimal outcome is predicated on an individualized treatment plan that integrates pharmacologic and behavioral modalities.

Role of nonesterified fatty acids in necrotizing pancreatitis: an in vivo experimental study in rats

INTRODUCTION

In acute pancreatitis, nonesterified fatty acids (NEFA) might be released by lipase and cause tissue necrosis by their detergent properties, but this has not been established in vivo.

AIMS

To measure the release of NEFA in the blood stream, pancreatic tissue, and peritoneal cavity during taurocholate-induced acute necrotizing pancreatitis in rats.

METHODOLOGY

Ascites and blood were repeatedly sampled; after 24 hours, pancreatic lesions were scored, and NEFA were measured in the pancreas. The effects of a specific lipase inhibitor (Tetrahydrolipstatin [THL]) were also studied.

RESULTS

A slight transient increase (22%) of NEFA concentration was observed in systemic circulation but did not parallel the time course of lipase activity, arguing against an intravascular production of NEFA by circulating lipase. Pancreatic NEFA did not differ between rats with pancreatitis and control rats. NEFA in ascites increased to threefold the basal value immediately after taurocholate and decreased rapidly thereafter, whereas lipase increased later in ascites and remained elevated during the 24-hour duration of the experiment. Lipase inhibition by THL neither modified the early increase of NEFA in ascites, nor altered the macroscopic, enzymatic, and histologic evolution of pancreatitis.

CONCLUSION

This in vivo study does not confirm the hypothetical role of NEFA produced by pancreatic lipase in the necrotic process and its systemic complications, up to now mainly suggested on the basis of ex vivo experiments.

Enhanced colonic peristalsis by impairment of nitrergic enteric neurons in spontaneously diabetic rats

Changes in enteric neurons containing various neurotransmitters in the colon have been described in diabetic rats; however, how these changes are related to colonic motility disorders remains unclear. Nitric oxide (NO) is known to be an important inhibitory neurotransmitter in the enteric nervous system. In the present study, we investigated the peristaltic reflex using our modified Trendelenburg's method to evaluate the differences in enteric nitrergic neurons of the distal colon between spontaneously diabetic rats and their sibling control rats. We measured maximum intraluminal pressure, threshold pressure and propagation distance of the reflex contraction. These diabetic rats showed a greater maximum intraluminal pressure than that in the control rats. NG nitro-L-arginine methyl ester (L-NAME) significantly increased the maximum pressure in the control rats. Although L-arginine did not change the maximum pressure, sodium nitroprusside (SNP) significantly decreased it in these diabetic rats. Nicotinamide adenine dinucleotide phosphate (NADPH) diaphorase reactivities in the myenteric plexus were much weaker in the diabetic rats than those in the control rats. These results indicate that the colonic peristaltic reflex is enhanced by impairment of enteric nitrergic inhibitory neurons in spontaneously diabetic rats.

Irritable bowel syndrome: an update on therapeutic modalities

Irritable bowel syndrome (IBS) is the most common condition that a physician faces in the GI clinic. Of the general population, 10 - 25% suffer from symptoms judged to be IBS. The negative impact of this disease includes not only pain, suffering and direct medical expenses but also significant social and job-related consequences. IBS can be the result of dysfunction in any part of the brain-gut axis: alterations in the CNS caused by psychological or other factors, abnormal gastrointestinal motility, or heightened visceral sensations. Diagnosis is based on either the Manning or Rome-II criteria. Education, reassurance and emotional support are the cornerstones of successful treatment. The mainstays of the current therapeutic approach continue to be: stress management strategies, dietary modification entailing addition of dietary fibre and pharmacotherapy. Pharmacotherapy is still limited to treating symptoms. Newer drugs that modulate motility or drugs that modulate visceral sensation may be useful in selected cases. Psychopharmacological agents are useful in the treatment of IBS, especially in those with psychological co-morbidity. Alternative therapies such as homeopathy, acupuncture, special diets, herbal medication and several forms of psychological treatments and hypnotherapy are sought by many patients and are now being offered by physicians as treatment options, either alone or in conjunction with conventional forms of therapy in patients with refractory symptoms.

Alterations in rectal sensitivity and motility in childhood irritable bowel syndrome

BACKGROUND & AIMS

Children with chronic abdominal pain have a heterogeneous clinical presentation, but no organic cause can be identified in most of them. Some children present with symptoms of irritable bowel syndrome (IBS). We hypothesized that visceral hypersensitivity and motor abnormalities may be underlying mechanisms in these children.

METHODS

Rectal sensation and rectal contractile response to a meal were studied in 8 children with IBS and 8 children with functional abdominal pain (FAP) and were compared with those of 9 healthy volunteers (HVs).

RESULTS

The threshold for pain, but not that for first sensation and urge to defecate, was significantly decreased in IBS patients (6 +/- 1 mm Hg) compared with FAP patients and HVs (17 +/- 1 and 22 +/- 2 mm Hg, respectively). In HVs and patients with FAP, ingestion of a meal induced a decrease in rectal volume with an early and late component. This motor pattern was absent in children with IBS. In IBS patients, no rapid volume waves were observed during fasting in contrast to FAP patients (2.7 +/- 0.3/10 min) and HVs (1.8 +/- 0.5/10 min).

CONCLUSIONS

Children fulfilling the Rome II criteria for IBS have a significantly lowered threshold for pain and a disturbed contractile response to a meal. Comparable to results reported in adults, sensory and motor abnormalities might play a pathophysiologic role in childhood IBS.

Correlation of symptom criteria with perception thresholds during rectosigmoid distension in irritable bowel syndrome patients

OBJECTIVE

Due to a lack of reliable biological markers, the diagnosis of irritable bowel syndrome (IBS) is based on symptom criteria. The possible physiological correlates of these criteria are not known. Our aims were to identify correlations of currently used IBS symptom criteria with distinct alterations in visceral perception.

METHODS

Forty-two IBS patients (51% women) with a mean age of 39.5+/-1.4 yr, were included; 64% of patients were recruited from advertisement and 36% were clinic referrals. Patients completed a bowel symptom questionnaire, which included the Rome criteria and symptom severity ratings. Rectal discomfort thresholds were evaluated in all patients and in 19 controls, using a nonbiased tracking protocol consisting of phasic rectal balloon distensions before (PreTh) and after (PostTh) repetitive, high-pressure sigmoid distensions. We assessed the effect of each Rome criteria and symptom severity on PreTh and PostTh.

RESULTS

IBS symptom severity was reported as moderate in 38.1% and as severe in 61.9% of patients. Overall, lower thresholds were observed in IBS patients than in controls (PreTh: 28.2+/-1.7 vs. 36.3+/-2.8 mm Hg, p<0.05; PostTh: 25.3+/-1.5 vs. 34.2+/-2.7 mm Hg, p<0.01). When assessing the effect of Rome criteria on rectal thresholds, we found that patients with hard/lumpy stools had lower thresholds than those without them, whereas patients with loose watery stools had higher thresholds than those who lacked them (both p<0.05). The lowering of rectal discomfort thresholds after sigmoid stimulation was observed regardless of the presence or absence of any Rome criteria or symptom severity.

CONCLUSION

Although a decrease in rectal discomfort thresholds after sigmoid stimulation is seen in IBS regardless of specific symptoms, baseline and postsigmoid stimulation thresholds are lower in IBS patients with constipation-related symptoms.

Emerging disease model for functional gastrointestinal disorders

In response to perceived or experienced change that is considered threatening to the individual, the central nervous system mounts a stereotypic response that decreases the sensitivity to pain, modulates the autonomic nervous system outflow, and activates the hypothalamic-pituitary-adrenal (HPA) axis. This response of the "emotional motor system" may or may not be associated with the conscious experience of feelings of fear or anxiety. Alterations in these response systems (either up- or downregulation) may produce symptoms, such as viscero-somatic hypersensitivity, altered bowel habits, or increased anxiety.

Colonic motility in man: features in normal subjects and in patients with chronic idiopathic constipation

The human colon is still a relatively unknown viscus, especially concerning its motor activity. However, in recent years, techniques have been perfected that allow a better understanding of colonic motility, especially through prolonged recording periods. In this way, it has been demonstrated that the viscus contracts according to a circadian trend, is responsive to physiological stimuli (meals, sleep), and features high amplitude, propulsive contractions that are part of the complex dynamic of the defecatory process. These physiological properties and their alterations in patients with chronic idiopathic constipation are reviewed in this article.

Regional effects of cholecystokinin octapeptide on colonic phasic and tonic motility in healthy humans

The aim of this study was to assess in nine healthy subjects the effects of CCK octapeptide (CCK-8) on colonic tonic activity, measured by a barostat, and phasic activity, measured by manometry. On 2 consecutive days, recordings were performed in the unprepared proximal and distal colons during intravenous infusion of saline and CCK-8 at 5, 20, and 40 ng. kg-1. h-1. In the proximal colon CCK-8 induced, at the 20 and 40 ng. kg-1. h-1 doses, a tonic relaxation with an increase in barostat bag volume to 156 +/- 25 and 157 +/- 19% of basal (P < 0.01) and a decrease in phasic activity to 72 +/- 7 and 76 +/- 7% of basal (P < 0.01). In the distal colon, CCK-8 induced, at the 20 and 40 ng. kg-1. h-1 doses, a tonic relaxation (increase in intrabag volume to 133 +/- 12 and 149 +/- 15%, respectively; P < 0.01), whereas phasic activity increased (128 +/- 8 and 132 +/- 6%, respectively; P < 0.01). Effects of CCK-8 on tonic and phasic activities are different according to the colonic segment. Because meals induce colonic tonic contraction, our results suggest that CCK, as a hormone, is not an important mediator of the response of the colon to feeding in humans.

Idiopathic constipation: too few stools and too little knowledge

The precise abnormalities of colonic motility patterns in idiopathic constipation, and the alterations at the cellular, neural, myogenic and biochemical levels that underlie these patterns, are not yet understood. One promising approach in the treatment of constipation seems to be to design drugs that can stimulate GMCs to produce mass movements and consequently defaecation. This could possibly be achieved with the selective 5-HT4 receptor agonists prucalopride and SDZ HTF-919, which are currently in advanced clinical trials. Other mechanisms that provide a means to induce GMCs, such as NK1 receptor agonism, deserve further exploration.

Functional gut disorders: from motility to sensitivity disorders. A review of current and investigational drugs for their management

Functional gut disorders include several clinical entities defined on the basis of symptom patterns (e.g., functional dyspepsia, irritable bowel syndrome, functional abdominal pain, functional abdominal bloating), for which there is no established pathophysiological mechanism. Because there is no well-defined pathophysiological target, treatment should be aimed at symptom improvement. Prokinetics and antispasmodics have been widely used in the treatment of functional gut disorders on the assumption that disordered motility is the underlying cause of symptoms, and symptom improvement is indeed achievable with these compounds in some, but not all, patients with features of hypo- or hypermotility, respectively. In the first part of this review, we cover the basic pharmacology and discuss the rationale for the clinical use of prokinetics and antispasmodics. On the other hand, in the past few years, the explosive growth in the research focusing on visceral sensitivity and visceral reflexes has suggested that at least some patients with functional gut disorders have altered visceral perception. Thus, the second part of the review covers these developments and focuses on studies addressing the issue of drugs modulating visceral sensitivity.

Effect of some gastrointestinal hormones on antral, small intestinal and caecal myoelectrical activity in the conscious miniature pig

The effect of i.v. infusion of gastrin (CCK-4), cholecystokinin (CCK-8) and pancreatic polypeptide (PP), 20 and 200 ng/kg/min for 1 h, on gastrointestinal electrical activity and arterial pressure was studied in conscious miniature pigs. During infusion of CCK-8 a transient hypertension was observed. In the antrum, the 3 peptides provoked an increase in slow wave activity and a decrease in spike activity. In the intestine, CCK-8 induced an increase in ileal spiking activity, whereas infusion of PP resulted in an increased frequency of long spike bursts in the caecum.

Endogenous CCK inhibits colonic contractions in unrestrained conscious rats

As cholecystokinin octapeptide (CCK-OP) and feeding have been reported to relax the circular muscle contractions of the proximal colon in unrestrained conscious rats under fasting conditions, the, action of cholecystokinin, released after duodenal infusion of a low residual diet of clinimeal, was studied on the motor activity of the proximal colon in unrestrained conscious rats. We used an implantable telemetry system with a miniature strain gauge force transducer introduced into the rat proximal colon. By using a specific radioimmunoassay system for CCK, plasma levels of CCK before and after duodenal infusion of clinimeal (0.5, 1.0, 2.0 ml) were determined at 0, 5, 10, 20, 30, 60 min in the portal blood. The clinimeal infusion caused a significant increase in CCK levels of the portal plasma during 5 and 30 min. This increase was in a dose-dependent manner. In accordance with this increase in plasma CCK, the motor activity of the proximal circular muscle was suppressed significantly. A bolus injection of the CCK A receptor antagonist, loxiglumide, CR 1505 (0.1, 0.5 and 1.0 mg/kg ip), prior to clinimeal blocked the inhibitory action of CCK on the motor activity in a concentration-dependent manner. These data suggest that endogenous CCK released by a residual diet is involved in the mechanism of inhibition of motor activity in the proximal colon.

Disturbed motilin and cholecystokinin release in the irritable bowel syndrome

BACKGROUND

The irritable bowel syndrome (IBS) is associated with motor abnormalities in the small intestine and colon. Neuropeptides may have an important role in initiating and regulating the intestinal motility. Motilin has been proposed to initiate the peristaltic reflex in the small intestine and cholecystokinin the gastrocolic reflex.

METHODS

In 18 patients with IBS and 11 healthy control subjects plasma motilin and cholecystokinin (CCK) concentrations were measured after intraluminal stimulation of water and a fat-rich meal.

RESULTS

The IBS patients had reduced motilin secretion after both water intake and the fat meal. In contrast, the fat meal elicited an exaggerated and prolonged CCK release in the IBS patients.

CONCLUSIONS

Disturbed motilin and CCK release may partly be responsible for the intestinal dysmotility in the IBS patients.

Pharmacological profile of TP-680, a new cholecystokininA receptor antagonist

1. The pharmacological characteristics of a newly developed serine derivative (R)-1-[3-(3-carboxypyridine-2-yl) thio-2-(indol-2-yl)carbonylamino]propionyl-4-diphenylmethyl- piperazine (TP-680), a cholecystokinin type A (CCKA) receptor antagonist, were studied and compared with those of MK-329 and loxiglumide. 2. TP-680 showed approximately 2 and 22 times greater selectivity for peripheral CCKA receptors relative to brain CCK (CCKB) receptors than MK-329 and loxiglumide, respectively, when IC50 values for inhibition of [125I]-CCK-8 binding in isolated acini and cerebral cortex were compared. 3. TP-680 was approximately 17 times less potent than MK-329, but was 106 times more potent than loxiglumide in inhibiting 100 pM CCK-8-stimulated amylase release from rat pancreatic acini. The antagonism produced by TP-680 was specific for CCK in that the effects of other receptor secretagogues or agents bypassing receptors were not altered. 4. TP-680 caused a parallel rightward shift of the dose-response curve for CCK-8-stimulated amylase release as did MK-329 and loxiglumide. However, in contrast to MK-329 and loxiglumide, TP-680 suppressed the maximal responses of CCK-8-induced amylase release in a concentration-dependent fashion, indicating that TP-680 is an unsurmountable antagonist. 5. Repeated washing of acini after a 30 min treatment with TP-680 restored the responsiveness but not the sensitivity, causing a residual inhibition on the action of CCK-8. 6. The addition of loxiglumide prior to or together with application of TP-680 protected CCK receptors from unsurmountable and irreversible antagonism by TP-680. 7. Our results indicate that TP-680 is a potent and the most selective CCKA receptor antagonist for the pancreas reported to date.

Colonic motility in health and disease

Being the final pathway for chyme and digestive residues, the colorectum influences bowel function critically. The most important and relevant symptoms of colonic dysfunction are diarrhea, constipation, urgency, and pain. Despite the effects of many investigators, over several decades, the motor physiology of the human colon is still relatively obscure. Most is known about patterns of colonic transit. In practice, measurements of transit are the best characterized and most widely available tests of colonic motor function. Colonic hypersensitivity, implying an abnormality of afferent signaling, is assuming greater importance in the pathophysiology of conditions as common as IBS and inflammatory bowel disease.

Therapeutic strategies for motility disorders. Medications, nutrition, biofeedback, and hypnotherapy

Gastrointestinal motility is regulated by a complex balance of inhibitory and excitatory neuronal, humoral, and mechanical factors. The goal in the management of motility disorders is to maintain adequate nutrition while decreasing symptoms. This can be accomplished by medications and support of nutrition and biofeedback; the application of these therapeutic strategies to patients with gut motility disorders is reviewed.

Effects of CCK-receptor antagonist on colonic motor activity in dogs

This study employed a cholecystokinin (CCK) antagonist to evaluate whether endogenous CCK regulates fasted and fed motor patterns of the colon. Experiments were performed in six conscious dogs, each in duplicate. Motor activity was recorded by four strain gauge transducers implanted on the colon. The effects of the CCK-analogue caerulein and the CCK-antagonist loxiglumide (Rotta, Italy) were studied in fasted and fed states. The motor activity was computed for the area under contractions. Caerulein given as an intravenous bolus of 50 ng kg-1 during a quiescent state caused a burst of phasic and tonic contractions resembling a regular non-migrating motor complex. Physiological doses of 10 ng kg-1 caerulein, which increases plasma CCK-immunoreactivity to postprandial levels, had no effect. Continuous intravenous infusion of 10 mg kg-1 h-1 loxiglumide completely abolished the effects of 50 ng kg-1 caerulein. The motor activity stimulated by the cholinesterase inhibitor neostigmine (10 micrograms kg-1) was not altered by loxiglumide. Loxiglumide given in the fasted state reduced the area under contractions in the proximal colon by 26.8 +/- 12.8% compared to the control without loxiglumide (P < 0.05). The postprandial increase in motor activity in the distal colon, the gastrocolonic response, was significantly inhibited by loxiglumide. Moreover, loxiglumide reduced the area under contractions in the fed state by 25.4 +/- 10.7% and 19 +/- 7.2% in the proximal and distal colon, respectively (P < 0.05). The present results show that loxiglumide acts as a specific antagonist of the actions of CCK on colonic motor activity in the dog.(ABSTRACT TRUNCATED AT 250 WORDS)

Irritable bowel syndrome. Managing the patient with abdominal pain and altered bowel habits

Irritable bowel syndrome is a common complex of syndromes thought to be generated by a motility or sensory disturbance of the gastrointestinal tract. It is a frequent cause of chronic abdominal pain and altered bowel habits. Patients who seek medical attention for irritable bowel syndrome often do so because of psychosocial factors. Therapy remains largely empirical, directed toward the relief of symptoms in the context of a supportive physician-patient relationship.

Human colonic motility: physiological aspects

From the point of view of its motor activity, the human colon is probably the least understood of the abdominal hollow viscera. This is due to several facts: a) its proximal portions are relatively inaccessible due to anatomical reasons; b) there is no reliable animal model due to the considerable anatomic-physiological differences among mammals. For instance, most deductions about human colonic motor activity have been drawn from experiences in cats and dogs, in which the colon displays a cecum which is almost atrophic, and the viscus is featureless and C-shaped, without the haustrations and the sharp angulations seen in man, c) the wide fluctuations of motility in the daily time course of the same individual makes the interpretation of many studies difficult, especially considering the fact that, until recently, most of the studies on human colonic motility have been conducted for relatively short (30-180 min) recording periods. Recently, however, techniques that allow recording from the proximal portions of the human colon have been developed, and prolonged (24 h or more) observations of myoelectrical and contractile events have been achieved, thus improving our knowledge of the normal physiologic properties of the viscus. These informations have furthermore been integrated and confirmed by scintigraphic techniques (less invasive), that allow the measurement of intracolonic flow activity. The purpose of the present paper is to review the physiological aspects of colonic motility in man, quoting animal studies where human ones are lacking. We will briefly introduce some basic concepts, then a more detailed description of the main topic will follow.