Gut hormones in acute diarrhoea

Cholera and Pancreatic Cholera: Is VIP the Common Pathophysiologic Factor?

Background: Cholera remains a major global health problem, causing high output diarrhea leading to severe dehydration and shock in developing countries. We aimed to determine whether vasoactive intestinal polypeptide (VIP), the mediator of pancreatic cholera syndrome, has a role in the pathophysiology of human cholera. Methods: We conducted a prospective observational study of cholera cases hospitalized with severe dehydration. Plasma and stool water levels of VIP were measured just after admission, after complete rehydration (3–4 h), at 24 h post-rehydration and at discharge after diarrhea ceased. Results: In total, 23 cholera patients were examined between January and August 2018. The geometric mean of stool VIP (sVIP) and plasma VIP (pVIP) on admission were 207.67 and 8.34 pmol/L, respectively. pVIP values were all within the normal range (</= 30 pcmol/L); however, sVIP levels were very high at all timepoints, though less so just after rehydration. In multivariable GEE models, after adjustment for covariates, sVIP levels were significantly associated with duration of hospitalization (p = 0.026), total stool volume (p = 0.023) as well as stool output in the first 24 h (p = 0.013). Conclusions: The data suggest that VIP, which is released by intestinal nerves, may play an important role in human choleragenesis, and inhibitors of intestinal VIP merit testing for potential therapeutic benefits.

Maternal smoking and infantile gastrointestinal dysregulation: the case of colic

BACKGROUND

Infants' healthy growth and development are predicated, in part, on regular functioning of the gastrointestinal (GI) tract. In the first 6 months of life, infants typically double their birth weights. During this period of intense growth, the GI tract needs to be highly active and to function optimally. Identifying modifiable causes of GI tract dysregulation is important for understanding the pathophysiologic processes of such dysregulation, for identifying effective and efficient interventions, and for developing early prevention and health promotion strategies. One such modifiable cause seems to be maternal smoking, both during and after pregnancy. Purpose. This article brings together information that strongly suggests that infants' exposure to tobacco smoke is linked to elevated blood motilin levels, which in turn are linked to an increased risk of GI dysregulation, including colic and acid reflux. We base this hypothesis on evidence supporting a link between maternal smoking and infantile colic (IC) and on additional evidence proposing increased motilin release, attributable to exposure to tobacco smoke and its metabolites, as a physiologic mechanism linking maternal smoking with infantile GI dysregulation.

METHODS

We critically review and synthesize epidemiologic, physiologic, and biological evidence pertaining to smoking and colic, smoking and motilin levels, and motilin and colic.

RESULTS

Six studies have investigated the link between maternal smoking and IC, but IC was defined according to Wessel's rule of threes (crying for > or =3 hours per day, > or =3 days per week, for > or =3 weeks) in only 1 of these studies. The remaining studies used definitions that ranged from less-stringent variations of Wessel's criteria to definitions that would suggest excessive crying but not necessarily colic. Results from 5 of these studies suggest that there is an independent association between maternal smoking and excessive crying, as well as IC. Recent studies of the GI system provide strong, but indirect, corroborating evidence suggesting physiologic pathways through which maternal smoking can be linked to IC. This physiologic evidence can be outlined as follows: (1) smoking is linked to increased plasma and intestinal motilin levels and (2) higher-than-average levels of motilin are linked to elevated risks of IC. Although these findings from disparate fields suggest a physiologic mechanism linking maternal smoking with IC, the entire chain of events has not been examined in a single cohort. A prospective study, begun in pregnancy and continuing through the first 4 months of life, could provide definitive evidence linking these disparate lines of research. Key points for such a study are considered.

CONCLUSIONS

New epidemiologic evidence suggests that exposure to cigarette smoke and its metabolites may be linked to IC. Moreover, studies of the GI system provide corroborating evidence that suggests that (1) smoking is linked to increased plasma and intestinal motilin levels and (2) higher-than-average intestinal motilin levels are linked to elevated risks of IC. In the United States, nearly one-half of all women smokers continue to smoke during their pregnancies. This amounts to approximately 12% of all women who give birth. Moreover, it is estimated that 50% to 80% of employed adults have regular exposure to environmental tobacco smoke and that >30% of nonsmokers live with smokers. If, as we suspect, exposure to cigarette smoke increases the risk of colic, then this would provide additional incentives to parents to abstain from smoking. Decreased exposure to tobacco smoke can be expected to provide widespread and long-term health benefits to maternal and child populations.

Oxyntomodulin and glicentin are potent inhibitors of the fed motility pattern in small intestine

Glicentin (GLIC) and oxyntomodulin (OXM or GLIC 33-69) are gut hormones which regulate digestion. They are known to reduce digestive secretions and to delay gastric emptying. Their biological activities on intestinal motility are still unknown. The effect of a systemic GLIC or OXM increase was investigated in rats on the food intake, the postprandial myoelectrical activity of small intestine and the orocaecal transit. An OXM or GLIC i.v. infusion was applied during the 5 min preceding food onset and during the first 15 min of food intake. This determined a three- to fourfold increase of the preprandial OXM-GLIC level. The OXM or GLIC plasma increase did not modify food intake. OXM infusion slowed down gastric emptying when the stomach contained 3/4 of the ingested food (before T 3 h). The quantity of food delivered in jejunum was subsequently smaller (P < 0.05). In the small intestine, the duration of postprandial myoelectrical activity (50-60 min g(-1) of ingested food) was reduced by 70% (P < 0.001) on duodenum or jejunum and by 54% (P < 0.01) on ileum in OXM-treated rats. An interdigestive motility profile was settled and an acceleration of both gastric emptying and transit rate was thereafter evidenced (after T 3 h). GLIC also reduced the duration of the postprandial myoelectrical activity on duodenum and jejunum (65 and 63% respectively, P < 0.05), but was not as efficient as OXM on ileum. In pathological states such as acute adult gastroenteritis, OXM and GLIC exhibit a two- to fivefold increase in their plasma concentrations. The present findings suggest that OXM and GLIC could, in that disease, contribute to exclude pathogens, due to their joined action on gut motility.

Screening of a large panel of gastrointestinal peptide plasma levels is not adapted for the evaluation of digestive damage following irradiation

The aim of this study was to assess the potential of gastrointestinal peptide plasma levels as biomarkers of radiation-induced digestive tract damage. To this end, plasma levels of substance P, GRP, motilin, PYY, somatostatin-28, gastrin, and neurotensin were followed for up to 5 days in pigs after a 16-Gy whole-body X-irradiation, completed by a histopathological study performed at 5 days. Each peptide gave a specific response to irradiation. The plasma levels of GRP and substance P were not modified by irradiation exposure; neither were those of motilin and PYY. Concerning gastrin, a 2-3-fold increase of plasma concentration was observed in pig, which presented the most important histological alterations of the stomach. The plasma levels of somatostatin, unchanged from 1 to 4 days after irradiation, was also increased by 130% at 5 days. In contrast, a diminution of neurotensin plasma levels was noted, firstly at 1 day (-88%), and from 3 days after exposure (-50%). The present study suggested that changes in gastrin and neurotensin plasma levels were associated with structural alterations of the stomach and ileum, respectively, indicating that they may be relevant biological indicators of radiation-induced digestive damage to these segments.

Diarrhea reduces the rates of cardiac protein synthesis in myofibrillar protein fractions in rats in vivo

Although chronic diarrhea affects heart function and morphology, the pathogenic mechanisms are unknown. It was our hypothesis that diarrhea imposes metabolic stress to inhibit the synthesis of new contractile proteins. To test this hypothesis, we investigated the effects of lactose-induced diarrhea in rats. The groups were: 1) freely fed controls, 2) rats with lactose-induced diarrhea or 3) pair-fed rats. After 1 wk, hearts from the rats were subjected to subcellular fractionation techniques to isolate the major protein fractions, including myofibrillar proteins. The rates of protein synthesis were measured with concomitant assay of cardiac composition and plasma analytes. In comparison with the control group, diarrhea induced the following changes (P < 0.05): a decrease in heart weight, reduced RNA and mixed protein contents and a reduction in the fractional rate of mixed protein synthesis. There was a reduction in the content of all protein fractions. The fractional synthesis rate was reduced only for the myofibrillar fraction. Plasma insulin-like growth factor-I, but not corticosterone, was reduced. Plasma cholesterol and triglyceride concentrations were also reduced. In comparison with the pair-fed group, diarrhea induced the following changes (P < 0.05): a reduction in heart weight and fractional rate of mixed protein synthesis, reduced myofibrillar absolute synthesis rate and increased sarcoplasmic/myofibrillar fractional synthesis rate ratio. Plasma bicarbonate, triglyceride and urea concentrations were reduced, with an increase in albumin. Diarrhea impaired cardiac biochemistry, including a reduction in protein content and synthesis. A substantial proportion of these changes is due to anorexia, but the selective reduction in the synthesis of contractile proteins is a feature exclusive to the diarrhea group and may be due to reductions in plasma insulin-like growth factor-I.

Oxyntomodulin reduces hydromineral transport through rat small intestine

Glicentin (GLIC) and oxyntomodulin (OXM) are released from the ileum and colon during digestion. Both hormones reduce fluid and proton secretion in the stomach. The luminal concentration of sodium and chloride underlying the nutrient absorption, the effect of OXM on electrolyte transport through the small intestine, was assessed in vivo using ligated loops and in vitro using Ussing chambers. In vivo, a zero transport state, estimated by the net water, chloride, and sodium fluxes, was observed when an 80 mM NaCl normoosmolar solution (274 mosm) was administered intraluminally. Active secretion was observed with hyperosmotic challenge (474 mosm). The amplitude of this active secretion increased 2.5- to 3-fold when an electrogenic challenge (NaCl 40 mM) was substituted to the hyperosmotic one. OXM (800 fmol/ml plasma) did not modify the basal transport in the duodenum or in the jejunum (t = 45 min). When active secretion was induced by the hyperosmotic challenge, OXM (200 fmol/ml plasma) had no effect on duodenal or jejunal transport (t = 50 min). When active secretion was induced by an electrogenic challenge, OXM (300 fmol/ml plasma) preferentially reduced the hydromineral transport in jejunum. In vitro, OXM also induced a reduction in the ion transport towards the jejunal lumen (EC50 = 20 pM), the amplitude of which depended upon the integrity of the tetrodotoxin-sensitive neurons. In conclusion, OXM was able to reduce the large secretion induced in rat jejunum in vivo by an electrogenic gradient. In vitro, the antisecretory effect of OXM was partly mediated by the neurons present in the intrajejunal wall.

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.

Diagnostic value of fasting plasma peptide concentrations in patients with chronic diarrhea

To evaluate the utility of screening for multiple gastrointestinal peptides in the evaluation of patients with chronic diarrhea, we studied 193 patients referred for evaluation of chronic diarrhea and eight patients with known peptide-secreting tumors as a reference group. Fasting plasma samples were assayed for motilin, neurotensin, pancreatic polypeptide, somatostatin, substance P, vasoactive intestinal polypeptide, gastrin-releasing peptide, and calcitonin during a protocol evaluation for causes of chronic diarrhea. Although none of the referred patients were found to have tumors, abnormal levels of one or more peptides were found in 86 of 193 patients (45%). Abnormal plasma peptide levels were sometimes as high in these patients as in patients with known peptide-secreting tumors and would have led to mistaken diagnoses of tumors much more often than they would have led to correct diagnoses. The positive predictive value of elevation of any assayed peptide was < 2% at realistic prevalence rates for peptide-secreting tumors; the negative predictive value of a series of normal results was > 99%, but much of this was due to the rarity of these tumors. Patients with chronic diarrhea should not be screened routinely with a panel of plasma peptide assays in an effort to detect tumors; instead, peptide levels should be ordered selectively. Elevated fasting concentrations of the plasma peptides measured in this study are most likely epiphenomena due to diarrhea and should not be the sole basis for invasive diagnostic or surgical management of these patients.

Role of motilin in the control of intestinal absorption, and gastric and biliary secretions in the rat

The effects of motilin on proline absorption and gastric and biliary secretions were examined in the rat. Prolonged intravenous administration of motilin (50 pmol/kg/min) significantly inhibited (P < 0.05) proline transport across the jejunum and reduced basal acid secretion to 40% of control value. The same concentration of motilin induced choleresis and increased bile output by 32%. Incubation of intestinal strips with different concentrations of motilin produced a dose-dependent inhibitory pattern of proline accumulation in the intestinal cells.

Gut regulatory peptides and intestinal permeability in acute infantile gastroenteritis

The plasma concentrations of seven gut regulatory peptides were measured in 11 infants suffering from acute gastroenteritis. Samples were taken at the time of the acute illness, upon reintroduction of feeding, and three months after recovery. These results were compared with controls. In the infants with diarrhoea, a massive increase in the fasting plasma mean (SEM) concentrations of enteroglucagon was found at the time of illness (1292 (312) v 79 (27) pmol/l), with concentrations of pancreatic glucagon, peptide tyrosine tyrosine, and motilin also being increased (17.8 (3.1) v 6.3 (1.1) pmol/l, 114.6 (15.2) v 37.0 (11.0) pmol/l, 217.6 (44.1) v 98.5 (18.3 pmol/l) respectively). The preprandial concentrations of motilin were found to be still increased at recovery (183.9 (35.4) pmol/l), but the concentrations of the other three peptides had returned to normal values. No differences in plasma concentrations of vasoactive intestinal polypeptide, neurotensin, or pancreatic polypeptide were found. An increased intestinal permeability was demonstrated at the time of diarrhoea by the urinary ratio of lactulose to mannitol, suggesting simultaneous gut damage. The effects of regulatory peptides may be relevant to the pathophysiology of gastroenteritis in infants.

Motilin and infantile colic. A prospective study

Two hundred and nineteen infants, consecutively born, took part in a prospective study of infantile colic from birth to 12 weeks of age. The prevalence of infantile colic in this group was 17.4%. S-motilin was studied in 78 term infants (19 with and 59 without infantile colic) at birth (cord blood), at one day, and at 6 and 12 weeks of age, respectively. Basal motilin levels were raised both in cord blood (p less than 0.01) and in blood from neonates (p less than 0.001) who developed colic as well as in 6 week (p less than 0.05) and in 12-week-old infants with colic (p less than 0.01). Formula-fed infants with colic had higher basal motilin levels than formula-fed controls at 6 and 12 weeks of age (p less than 0.05). Breast-fed infants with colic had higher basal motilin levels than breast-fed controls at 12 weeks of age (p less than 0.05). The raised levels of motilin from the first day of life in infants who develop infantile colic might indicate that the gastrointestinal tract is affected in infants with infantile colic, before any symptoms of colic appear.

Gut hormone responses after reconstructive surgery for ulcerative colitis

After colectomy, continent ileal reservoirs are an accepted alternative to conventional ileostomy for patients with ulcerative colitis. To assess the effect of these reservoirs on digestive function, circulating and morphologic gut endocrine responses were measured in patients with a continent ileostomy or with a pelvic pouch and compared to patients with conventional ileostomy, with active ulcerative colitis and healthy controls. Eight subjects were studied in each group. Basal and postprandial plasma gastrin, enteroglucagon, neurotensin, vasoactive intestinal polypeptide, insulin, pancreatic glucagon, and pancreatic polypeptide in both groups with ileal reservoirs were equivalent to controls. Basal plasma motilin and postprandial plasma gastric inhibitory polypeptide were raised in ileal reservoir patients, but similar changes also occurred in ulcerative colitis patients and those with conventional ileostomy. In one half of patients, cell populations of enteroglucagon, peptide YY, and neurotensin were decreased in pouch mucosa that corresponded with the presence of mucosal inflammation. On the other hand, with pouch inflammation vasoactive intestinal polypeptide immunoreactive nerves were increased and a proportion of the fibres were moderately coarsened. Mucosal concentrations of vasoactive intestinal polypeptide did not, however, exceed that of controls. After an ileal reservoir sufficient reserve remains for gut hormone release into the circulation, suggesting compensation for the presence of a reservoir and the absence of a colon; circulating hormone changes do occur but are consequent upon previous ulcerative colitis. Reservoirs may show neuromorphologic alterations that appear to be related to mucosal inflammation.

Glucagon-like peptide-1 7-36: a physiological incretin in man

The physiological role of glucagon-like peptide-1 7-36 amide (GLP-1 7-36) in man was investigated. GLP-1 7-36-like immunoreactivity was found in the human bowel; its circulating level rose after oral glucose and after a test breakfast. When it was infused into seven volunteers at a rate to mimic its postprandial plasma concentration in the fasting state, plasma insulin levels rose significantly and glucose and glucagon concentrations fell. During an intravenous glucose load, it greatly enhanced insulin release and significantly reduced peak plasma glucose concentrations, compared with a control saline infusion, even inducing postinfusion reactive hypoglycaemia. By comparison, infusion of glucose-dependent insulinotropic peptide (GIP) to physiological levels was less effective in stimulating insulin release. These observations suggest that GLP-1 7-36 is a physiological incretin and that it is more powerful than GIP. The observation of greatly increased postprandial plasma GLP-1 7-36 levels in patients with postgastrectomy dumping syndrome suggests that it may mediate the hyperinsulinaemia and reactive hypoglycaemia of this disorder.

Increased plasma motilin concentrations in small cell carcinoma of the lung

Plasma samples from 21 patients with small cell carcinoma of the lung were screened for pancreatic polypeptide, somatostatin, motilin, and vasoactive intestinal polypeptide. One patient had severe impairment of both renal and liver function. In the 20 remaining subjects vasoactive intestinal polypeptide concentrations were normal, and only two patients had increased concentrations of somatostatin. Increases in pancreatic polypeptide were detected more commonly (7/20), but these may have been non-specific age related increases. The major finding was high concentrations of motilin (greater than 496 pg/ml) in 17 of 20 patients. Plasma motilin was subsequently assayed in 16 more patients with lung cancer, including 10 patients with non-small cell carcinoma of the lung. At concentrations over 900 pg/ml plasma motilin appears to be a tumour marker for small cell carcinoma of the lung with acceptable sensitivity (59%) and specificity (78%). The origin of increased plasma motilin in small cell carcinoma of the lung was investigated. Bombesin (gastrin releasing peptide), a peptide known to stimulate the release of motilin in man, was, as in previous studies, detected in tumour but not in plasma, except in one patient out of 21. Immunohistochemical studies failed to detect motilin antigen in biopsy samples. Motilin tumour content was found to be low in tumour tissue from three patients with small cell carcinoma of the lung who had appreciable hypermotilinaemia and from three patients with non-small cell carcinoma of the lung who had either normal or slightly raised plasma motilin concentrations. The stimulus to motilin secretion in patients with small cell carcinoma of the lung remains unclear.

Motilin, vasoactive intestinal peptide and gastrin in infantile colic

Intestinal hyperperistalsis is one part of the clinical picture in infantile colic. Three gut hormones involved in the regulation of gut motility; motilin, vasoactive intestinal peptide (VIP) and gastrin, were measured with the RIA method in: 40 infants with infantile colic, (age 2-22 weeks), 42 healthy age-matched infants, 11 children (age 3-36 months) with gastrointestinal disorders, and 20 children (age 3-36 months) with non-gastrointestinal disorder. Basal s-motilin levels were raised in infants with infantile colic (p less than 0.01) and in children with other gastrointestinal disorders (p less than 0.001). Formula-fed infants had higher basal s-motilin levels than the breast-fed infants (p less than 0.05). P-VIP and s-gastrin levels were raised in children with other gastro-intestinal disorders (p less than 0.05), but not in infantile colic. Formula-fed colicky infants had higher s-gastrin levels than the breast-fed colicky infants (p less than 0.05). We suggest that the increased s-motilin level in infantile colic might account in part for the clinical picture of this disorder.

Gut hormones in adaptation

The presence of a circulating factor affecting gut growth can be surmised from the findings in gut isolated from the main food stream and not under direct nutritional influence. Thus when a Thiry Vella fistula is constructed and the crypt cell production rate counted in the fistula it can be shown to correlate with the degree of resection of the main bowel left in continuity. The only hormones which become raised in a similar pattern are enteroglucagon and peptide tyrosine tyrosine (PYY). Enteroglucagon has been shown to be part of preproglucagon, which contains in addition oxyntomodulin, glucagon like peptide 1 1-37 and 6-36NH2 and glucagon like peptide 2. These form the main candidates for the 'hormone of gut growth'. Peptide tyrosine tyrosine has been tested by direct administration over 12 days, matching the natural rise, but no affect on crypt cell production rate was seen. Glucagon like peptide 1 1-37 was similarly tested and also found to produce no effect. It remains to test the other members of the glucagon family to confirm or refute the hypothesis that one of them is the enigmatic small gut growth factor.

Motilin in chronic idiopathic constipation

The plasma motilin levels were studied in seven patients with severe long-standing idiopathic constipation before and after a fat-rich test meal. The results were compared with those of a control group consisting of 10 apparently healthy persons with normal bowel function. The constipated patients had reduced basal motilin levels and a reduced motilin release after the test meal. Motilin is known to stimulate intestinal motility by inducing interdigestive descending contractions in the stomach and small intestine. A defective motilin release may therefore play a part in the pathogenesis of idiopathic constipation.

Secretion of pancreatic polypeptide in patients with pancreatic endocrine tumors

Pancreatic polypeptide is often secreted by pancreatic endocrine tumors and is considered a marker for such tumors. To investigate the diagnostic value of this marker, we studied 323 patients with proved pancreatic endocrine tumors. We found plasma concentrations of pancreatic polypeptide to be elevated (more than 300 pmol per liter) in 144 patients (diagnostic sensitivity, 45 percent). However, plasma levels of pancreatic polypeptide can also be elevated in the absence of a pancreatic tumor. To ascertain whether the administration of atropine could distinguish between normal and tumor-associated polypeptide secretion, we studied 30 patients with pancreatic tumors and high plasma levels of pancreatic polypeptide, 18 patients without tumors who had elevated levels of pancreatic polypeptide, and eight normal controls. Polypeptide levels in the 18 patients without tumors were substantially lower than in the 30 patients with tumors. Atropine (1 mg intramuscularly) did not suppress polypeptide levels in patients with tumors, but did suppress plasma levels by more than 50 percent in all subjects without tumors. Thus, although its diagnostic sensitivity is low, pancreatic polypeptide appears to be a useful adjunctive marker of many pancreatic endocrine tumors, and the atropine suppression test can be used to distinguish normal from tumor-related secretion of the polypeptide. Identification of the type of pancreatic endocrine tumor still requires measurement of the hormone that is specific for the tumor.

Enterocyte-labelling index in the duodenal mucosa of patients with progressive systemic sclerosis (PSS)

Ten patients with progressive systemic sclerosis (PSS), 4 patients with other gastro-intestinal diseases and 5 normal controls, underwent small intestinal biopsy procedure. The biopsy material was incubated with tritiated thymidine and processed for auto-radiography. The labelling index (LI) in the small intestinal mucosa was estimated. The LI in PSS patients with duodenal involvement was significantly higher than the LI in PSS patients without duodenal involvement. In the latter group, the LI was at the same level as in normal controls. The LI in patients with other gastro-intestinal diseases, with diarrhoea as a main symptom, was not significantly different from the LI found in duodenal PSS.

Peptide YY abnormalities in gastrointestinal diseases

Plasma concentrations of peptide YY (PYY), a newly isolated peptide produced by ileal and colonic endocrine cells, were measured in several groups of patients with digestive disorders after a standardized normal breakfast. Peptide YY levels were found to be grossly elevated in patients with steatorrhea due to small intestinal mucosal atrophy (tropical sprue). Basal levels in these patients were 79 +/- 18 pM, which was nearly 10-fold higher than those seen in healthy controls (8.5 +/- 0.8 pM). Patients with steatorrhea due to chronic destructive pancreatitis also had substantially increased basal PYY levels (47.5 +/- 6.3 pM), and their postprandial response was also greater than that of normal subjects. Moderately elevated plasma PYY concentrations were seen in patients with inflammatory bowel disease and patients recovering from acute infective diarrhea. In contrast, patients with diverticular disease, duodenal ulcer, and functional bowel disease had normal PYY responses. These changes in the secretion of PYY responses. These changes in the secretion, may shed light on the physiologic role of this newly discovered peptide and on intestinal adaptation to common digestive disorders.

Positive correlation between symptoms and circulating motilin, pancreatic polypeptide and gastrin concentrations in functional bowel disorders

Motilin, pancreatic polypeptide and gastrin blood concentrations in response to drinking water have been studied in 40 patients with functional bowel disease and compared with results in two groups of healthy control subjects. Patients with slow transit constipation and idiopathic megacolon showed impaired motilin release. Pancreatic polypeptide release was reduced in patients with slow transit constipation, but increased in those with functional diarrhoea. Gastrin release was impaired in all groups complaining of chronic constipation. Circulating motilin, pancreatic polypeptide and gastrin concentrations appear to bear some relationship to intestinal transit time in patients with functional bowel disorders.

Motilin--an update

Motilin isolated in 1971 from the porcine gastrointestinal tract and localized there to endocrine cells, now appears to have a CNS neural origin by RIA and immunohistochemistry. In most species motilin releases neurotransmitters in the CNS to both increase and decrease neural transmission and in the gastrointestinal tract to increase motor activity. In the fasting animal, motilin initiates premature activity fronts of the migrating motor complex (MMC) in the upper gastrointestinal tract by an atropine or tetrodotoxin-sensitive mechanism. Immunoreactive motilin-release from the gut can be correlated with the passage of these fronts through the upper gut. In the dog, the associated events of this MMC, i.e. motor activity of the duodenum extrinsic and intrinsic neural activity and emptying of biliary and pancreatic secretions into the duodenum, all appear to contribute to the peaks in peripheral plasma immunoreactive motilin concentrations. In man, there appears to be a close association of motilin secretion with biliary and pancreatic secretions being emptied into the duodenum and less evidence for motor activity releasing motilin. Only in the dog is there strong evidence for an absolute requirement of motilin for the consolidation of the motor activity of the upper gut into the MMC. In man, the evidence is less convincing although motilin may facilitate the process and in the pig, motilin appears to have little or no role in MMC generation. No pathological consequences of hypermotilemia have been described although elevated motilin levels have been found to be associated with some diarrheal states, renal failure, and in the first week following abdominal surgery. Motilin thus remains a hormone seeking a physiological function in some species and a pathological role in all species.

Aetiology and pathogenesis of postinfective tropical malabsorption (tropical sprue)

Postinfective tropical malabsorption (TM; tropical sprue) starts with an acute intestinal infection (bacterial, viral, or parasitic) which can affect predominantly the small or the large intestine. Miscellaneous invasive pathogens cause subsequent enterocyte damage affecting the entire small intestine and, to a lesser extent, the colon. Enteroglucagon, a tropic hormone, is then liberated and reaches a high plasma concentration. Small-intestinal stasis results. Further bacterial colonisation (in the lumen and also at the enterocyte surface) is encouraged. Continuing enterocyte damage is worsened by coexistent folate depletion, which is initiated at the onset of disease; body stores of folate reach a low concentration by 3 or 4 months. The cycle continues until the bacterial overgrowth is eliminated with an antibiotic (eg, tetracycline), or mucosal integrity recovers (hastened by oral folic-acid supplements), or both.