Effect of nonpeptide motilin agonist EM523 on release of gut and pancreatic hormones in conscious dogs

Interaction of insulin with prokinetic drugs in STZ-induced diabetic mice

AIM: To study the possible interactions of metoclopramide, domperidone and erythromycin in streptozotocin-induced diabetic mice treated with insulin by various parameters.

METHODS: Effects of the individual as well as combined drugs were studied in diabetic mice via estimation of the blood glucose and serum insulin levels, small intestinal transit (SIT), gastric emptying (GE), xylose absorption and glucose tolerance tests. Groups were given insulin 2 IU/kg s.c., metoclopramide 20 mg/kg p.o., domperidone 20 mg/kg p.o. and erythromycin 6 mg/kg p.o. individually and in combination. There were also normal and diabetic control groups. The first set of experiments was carried out to investigate the subchronic effect on blood glucose and serum insulin levels in diabetic mice of one week of daily dose administration of the tested drugs individually as well as the combination of insulin with each prokinetic drug. The other five sets of experiments were carried out to investigate the acute effect of a single dose of each drug individually and in combination on blood glucose and serum insulin levels, SIT, GE, oral xylose absorption and glucose tolerance tests.

RESULTS: The study included the prokinetic drugs metoclopramide (20 mg/kg), domperidone (20 mg/kg) and erythromycin (6 mg/kg), as well as insulin (2 IU/kg), which was individually effective in decreasing SIT, enhancing GE and increasing xylose absorption significantly in diabetic mice. Erythromycin tended to decrease blood glucose level and increase serum insulin level after 1 wk of daily administration in diabetic mice. Erythromycin potentiated the effect of insulin on blood glucose level and serum insulin level whereas other prokinetic agents failed to do so after repeated dose administration in diabetic mice. Metoclopramide or erythromycin in combination with insulin significantly decreased SIT, in diabetic mice, to lower levels than with insulin alone. Administration of prokinetic drugs along with insulin antagonized the action of insulin on xylose absorption. These combinations also increased the rate of glucose absorption from the gut.

CONCLUSION: The present study suggests that prokinetic drugs could potentially improve glycemic control in diabetic gastroparesis by allowing a more predictable absorption of nutrients, matched to the action of exogenous insulin. The use of prokinetics, such as erythromycin, may be interesting in the clinic in decreasing the need for insulin in diabetic patients. The dose of insulin may be safely decreased with erythromycin in chronic treatments.

Therapeutic strategies for the management of delayed gastric emptying after pancreatic resection

BACKGROUND

Delayed gastric emptying (DGE) is one of the most troublesome postoperative complications following pancreatic resection. Not only does it contribute considerably to prolonged hospitalization, but it is also associated with increased postoperative morbidity and mortality.

METHODS

We performed an electronic and manual search of the international literature for studies dealing with the treatment of DGE following pancreatic resection using the Medline database. The search items used were "delayed gastric emptying," "pancreaticoduodenectomy," "Whipple procedure," "pylorus-preserving pancreaticoduodenectomy," and "complications following pancreatic resection" in various combinations.

RESULTS

A number of studies were identified regarding possible therapeutic alternatives for the treatment of DGE. From the class of prokinetic regimens, most studies seem to support the use of erythromycin. However, its use has not gained wide acceptance. Regarding the operative technique, both standard Whipple and pylorus-preserving pancreatic resection carry similar rates of DGE. Billroth II type-like gastrointestinal reconstruction is the most widely accepted method and is associated with lower rates of DGE. Reoperations for managing severe DGE were very rarely reported.

CONCLUSIONS

The incidence of DGE in high-volume centers specialized in pancreatic surgery is well below 20%, thus following the improved rates that have been reported in the last decade regarding mortality and length of hospital stay after pancreatic surgery. DGE mandates a uniform definition and method of evaluation to achieve homogeneity among studies. Standardization of the operative technique, as well as "centralizing" pancreatic resections in high-volume centers, should aid to improve the occurrence of this bothersome postoperative complication.

Heartburn-dominant, uninvestigated dyspepsia: a comparison of 'PPI-start' and 'H2-RA-start' management strategies in primary care--the CADET-HR Study

BACKGROUND

There are few data on empiric, stepped therapy for heartburn relief or subsequent relapse in primary care.

AIMS

To compare heartburn relief produced by a proton pump inhibitor-start or an H(2)-receptor antagonist-start with step-up therapy, as needed, followed by a treatment-free period to assess relapse.

METHODS

Heartburn-dominant uninvestigated dyspepsia patients from 46 primary care centres were randomized to one of two active treatment strategies: omeprazole 20 mg daily (proton pump inhibitor-start) or ranitidine 150 mg bid (H2-receptor antagonist-start) for the first 4-8 weeks, stepping up to omeprazole 40 or 20 mg daily, respectively, for 4-8 weeks for persistent symptoms. Daily diaries documented heartburn relief (score < or = 3/7 on < or = of 7 prior days) and relapse (score > or = 4 on > or = 2 of 7 prior days).

RESULTS

For 'proton pump inhibitor-start' (n = 196) vs. 'H2-receptor antagonist-start' (n = 194), respectively, heartburn relief occurred in 55.1% vs. 27.3% (P < 0.001) at 4 weeks and in 88.3% vs. 87.1% at 16 weeks. After therapy, 308 patients were heartburn-free (159 vs. 149); median times to relapse were 8 vs. 9 days and cumulative relapse rates were 78.6% vs. 75.8%, respectively.

CONCLUSIONS

An empiric 'proton pump inhibitor-start' strategy relieves heartburn more effectively than an 'H2-receptor antagonist-start' strategy up to 12 weeks but has no effect on subsequent relapse, which is rapid in most patients.

Effect of altering gastric emptying on postprandial plasma glucose concentrations following a physiologic meal in type-II diabetic patients

The purpose of this study was to determine the effects of altering gastric emptying on postprandial plasma glucose concentration after a physiologic meal in patients with type II diabetes mellitus (T II DM). Nine T II DM patients underwent a double-blind, randomized, three-way crossover study, receiving erythromycin 200 mg, morphine 8 mg, or normal saline (placebo) intravenously prior to ingestion of a radiolabeled, dual-isotope, solid-liquid meal. Gastric emptying of solids and liquids and serial plasma glucose, glucagon, and serum insulin concentrations were measured at baseline and for 5 hr after meal ingestion. Erythromycin accelerated and morphine delayed solid- and liquid-phase gastric emptying compared to placebo (P < 0.05). During the first hour, the postprandial plasma glucose concentrations were higher after erythromycin (P < 0.05) and lower after morphine (P < 0.05) compared to placebo. The peak postprandial plasma glucose concentration was higher after erythromycin (P = 0.05) and lower after morphine (P < 0.05) compared to placebo. In conclusion, pharmacologic acceleration of gastric emptying resulted in higher postprandial glucose concentrations, while delaying gastric emptying resulted in lower postprandial glucose concentrations after a physiologic meal in T II DM. These results suggest that administration of opiate analgesics or prokinetic agents to diabetic patients may alter glucose control. Modifying gastric emptying may be helpful in achieving glucose control in T II DM.

Octreotide enhances the accelerating effect of erythromycin on gastric emptying in healthy subjects

BACKGROUND

Erythromycin exhibits gastrokinetic properties through cholinergic pathways. Reports regarding the action of octreotide on gastric emptying are conflicting.

AIM

: To assess: (i) the hypothesis that serotonin receptors are involved in the accelerating effect of erythromycin on gastric emptying; and (ii) any modification of the gastrokinetic action of erythromycin induced by octreotide.

SUBJECTS AND METHODS

Gastric emptying of a standard meal was estimated in 20 healthy subjects by scintigraphy on three different occasions in a double-blind, placebo-controlled manner and in random order: (i) after placebo; (ii) after 200 mg of intravenous erythromycin; and (iii) after 200 mg of intravenous erythromycin following pre-treatment with either 4 mg of intravenous ondansetron (10 subjects) or 50 micro g octreotide.

RESULTS

Erythromycin significantly accelerated gastric emptying in all subjects by abolishing the lag phase. Pre-treatment with ondansetron abolished the accelerating effect of erythromycin by restoring the emptying times to placebo levels. Octreotide significantly enhanced the accelerating effect of erythromycin by reducing both the lag and post-lag phases of gastric emptying.

CONCLUSIONS

Serotonin receptors are involved in the accelerating effect of erythromycin on gastric emptying. This effect seems to be enhanced by pre-treatment with octreotide, possibly as a result of the modification of the gastrointestinal hormonal environment.

Design and synthesis of N-terminal cyclic motilin partial peptides: a novel pure motilin antagonist

Motilin antagonist was designed and synthesized on the basis of the structure-activity relationship analysis of porcine motilin that we reported recently. The drug design was performed on a specific concept to reduce a flexibility of peptide conformation of porcine motilin partial peptide by its cyclization. The cyclic peptide was synthesized using Boc (tert-butyloxycarbonyl) solid phase methodology, followed by cyclization using the azide procedure, and tested for the binding activity to motilin receptor and smooth muscle contractile activity. The cyclic peptides 3, 4, and 5 showed antagonistic property on contraction assay (pA2 [the negative logarithm of molar concentration of antagonist causing a 2-hold shift to the right of the concentration-response curve for motilin]: 4.5, 4.34, and 4.04, respectively, in rabbit duodenum) and no contractile activity even at high concentration.

The effect of erythromycin on human esophageal motility is mediated by serotonin receptors

OBJECTIVE

Erythromycin exhibits prokinetic properties. The drug enhances esophageal and gastric motility by acting as a motilin agonist and promoting acetylocholine release. 5-HT3 receptors are involved in the spontaneously occurring migrating motor complex and the effect of erythromycin on antral motility in dogs. The aim of the study was to investigate the hypothesis that 5-HT3 receptors are also involved in the action of erythromycin on the human esophagus.

METHODS

A total of 18 healthy volunteers underwent standard esophageal manometry on three different occasions in a double-blind, placebo-controlled, randomized manner, as follows: 1) after placebo, 2) after 200 mg of erythromycin i.v., and 3) after 200 mg of i.v. erythromycin subsequent to pretreatment with either 4 mg of i. v. ondansetron (serotonin receptor antagonist) (10 subjects) or 12 microg/kg of i.v. atropine (8 subjects).

RESULTS

Erythromycin significantly increased a) the amplitude of peristalsis at 5 cm (from 87 +/- 19 mm Hg to 108 +/- 26 mm Hg; p = 0.0007), 10 cm (from 72 +/- 24 mm Hg to 81 +/- 26 mm Hg; p = 0.016), and 15 cm (from 47 +/- 15 mm Hg to 55 +/- 17 mm Hg; p = 0.014) proximal to LES, b) the duration of peristalsis at 5 cm (from 4.5 +/- 0.9 s to 5.7 +/- 1.2 s; p < 0.0001) and 10 cm (from 4.1 +/- 1 s to 4.9 +/- 1 s; p < 0.0001) proximal to the LES and c) the strength of peristalsis at 5 cm proximal to the LES (from 180 +/- 49 mm Hg x s to 276 +/- 100 mm Hg x s; p < 0.0001), and decreased the velocity of peristalsis at distal esophagus (from 4.1 +/- 1 cm/s to 3.8 +/- 0.9 cm/s; p = 0.03). In addition, erythromycin significantly increased the resting pressure of the LES (from 36 +/- 10 mm Hg to 44 +/- 12 mm Hg; p = 0.002). Pretreatment with ondansetron totally reversed all of the effects of erythromycin to the placebo state. Pretreatment with atropine not only prevented the effects of erythromycin, but it reduced the amplitude and strength of peristalsis at the distal esophagus at significantly lower levels than after placebo.

CONCLUSIONS

Erythromycin exerts its prokinetic action on the lower esophagus by stimulating cholinergic pathways. This action includes not only an increase in LES pressure, but significant increases in the amplitude and duration of esophageal peristalsis, as well. 5-HT3 receptors are also involved in this process.

Peripheral or central administration of motilin suppresses LH release in female rats: a novel role for motilin

Motilin is secreted in a clear episodic pattern during fasting or during the interdigestive phase, but feeding promptly stops this secretory pattern, and plasma concentrations of motilin decrease. We have previously determined that fasting markedly suppresses pulsatile luteinizing hormone (LH) secretion in female rats in the presence of oestrogen. In the present study, we wished to learn if motilin may mediate the fasting-induced suppression of LH secretion by determining the effects of motilin administration on LH release and on food intake. Intravenous (i.v.) injection of motilin (37 nmol/rat) suppressed LH release and significantly decreased mean LH concentrations both in ovariectomized (OVX) and oestradiol-implanted ovariectomized (OVX+E2) rats. Food intake was significantly increased by i.v. motilin injection in OVX rats, but not in OVX+E2 rats. It is likely that motilin inhibits LH release via inhibition of the gonadotrophin-releasing hormone (GnRH)-releasing mechanism at the hypothalamic level, because motilin (3.7 nmol/rat) also suppressed LH secretion when centrally administered, and because LH release in i.v. motilin-treated rats increased in response to exogenous GnRH. These results suggest that motilin may be a peripheral signal for the suppression of LH secretion through central sensors.

Esophageal hypersensitivity may be a major cause of heartburn

OBJECTIVE

Little is known about esophageal nociceptive thresholds in chronic heartburn sufferers with normal clinical findings. The aim of this study was to evaluate and to characterize the pathogenesis of heartburn in subjects who chronically use antacids and had not sought medical attention.

METHODS

Subjects (N = 152) with chronic heartburn of > or = 3 months duration underwent endoscopic grading of the esophagus, esophageal manometry, Bernstein testing, intraesophageal balloon distention (IEBD), and 24-h esophageal pH monitoring.

RESULTS

Normal acid contact time (ACT < or = 6%) was observed in 43% of these subjects with recurrent heartburn. Of subjects with normal ACT, 64% had normal LES pressure (> or = 10 mm Hg), 79% had normal esophageal endoscopy, 89% developed heartburn during Bernstein acid infusion, and 52% perceived IEBD as painful.

CONCLUSIONS

Approximately 30% of individuals chronically using antacids for heartburn had esophageal sensitivity to mechanical or chemical stimuli despite negative endoscopy and pH monitoring. Our findings suggest that a significant subset of typical heartburn sufferers have a lower threshold for esophageal sensation and pain, which may influence options for pharmacological intervention in such subjects.

The effect of motilin on the regulation mechanism of intestinal motility in conscious horses

Laparotomy was performed on seven thoroughbreds to attach a force transducer to the proximal jejunum, distal jejunum, and ileum, as well as to the serous membrane of the cecum. Following observation of intestinal motility in conscious horses, they were intravenously injected with motilin (0.6 microgram/kg) to examine its effect on intestinal motility. Strong contractions peculiar to horses were observed in small intestine. Further, motilin caused strong contractions in the proximal jejunum. The results suggested the involvement of motilin in the regulation mechanism of intestinal motility.

Correlation of ambulatory 24-hour esophageal pH monitoring results with symptom improvement in patients with noncardiac chest pain due to gastroesophageal reflux disease

Gastroesophageal reflux disease (GERD) accounts for up to 60% of patients with noncardiac chest pain (NCCP). Twenty-four-hour esophageal pH monitoring has been considered the most sensitive test for identifying acid reflux as the probable cause for chest pain. It is unclear if there is a correlation between the degree of esophageal acid exposure as determined by 24-hour esophageal pH monitoring and symptom improvement during a short course of high-dose omeprazole (the omeprazole test) in patients with NCCP due to GERD. Twenty-three patients with GERD-related NCCP were studied. All patients were referred by a cardiologist and evaluated by upper endoscopy and 24-hour esophageal pH monitoring. Diagnosis of GERD was defined by one or both tests being abnormal. Subsequently, patients underwent baseline symptom intensity assessment during 1 week off therapy followed by 1 week on therapy with high-dose omeprazole (40 mg A.M. and 20 mg P.M.). There was a statistically significant correlation between the esophageal acid exposure by 24-hour esophageal pH monitoring and the change in symptom intensity score after treatment. However, there was no significant correlation between the pH values and symptom intensity score during baseline or during the omeprazole test. In patients with GERD-related NCCP undergoing the omeprazole test, 24-hour esophageal pH monitoring has a therapeutic predictive value in addition to its diagnostic merit. Patients with greater esophageal acid exposure appear to have a greater response to antireflux treatment.

Noninvasive diagnosis of gastroesophageal inflammation using dipyridamole thallium-201 tomography

OBJECTIVE

Esophagitis, a complication of GERD, and gastric erosions are common findings in dyspeptic patients. Unfortunately, these findings cannot be predicted based on symptoms alone and require endoscopy for an accurate diagnosis. Noninvasive diagnosis of other gastrointestinal pathology by radiopharmaceuticals (GA 67, Tc 99m pertechnetate) has previously been studied. We hypothesized that endoscopically documented esophagitis and/or gastric erosions could also be detected by using dipyridamole thallium-201 imaging and, if they were of sufficient accuracy, could serve as a useful, noninvasive screening test for esophagitis and/or gastric erosions.

METHODS

A pilot study was undertaken in 12 patients undergoing endoscopy for symptoms of GERD or dyspepsia. Esophagitis was defined as the presence of either erosions or ulceration and gastric erosions were defined as discrete mucosal breaks measuring > or = 1 mm. Dipyridamole thallium-201 imaging was performed the following day on all 12 patients. A standard dose of dipyridamole (0.56 mg/kg) was infused over 4 min, followed by a 3-mCi dose of thallium-201. Initial stress tomographic images and reinjection (1 mCi) resting tomographic images 3-4 h later were obtained using a gamma camera. Tomographic images were read blinded to the endoscopy results. Thallium-201 uptake was graded on a 0-3+ scale using the liver uptake as the internal comparative standard (2+ = uptake equal to the liver). Abnormal thallium uptake was defined as > or = 2+ in the area of the esophagus or stomach.

RESULTS

Seven women and five men (mean age 41 yr, range 25-60 yr) were studied. Eight patients were taking histamine-2 receptor antagonists and none were on proton pump inhibitors, or promotility agents. All five patients with endoscopic esophagitis had a positive thallium-201 tomographic image. Seven patients had no evidence of esophagitis, and three had positive thallium-201 tomograms. Dipyridamole thallium-201 imaging sensitivity, specificity, and positive and negative predictive values for esophagitis were 100%, 57%, 63%, and 100%, respectively. All three patients with gastric erosions had positive thallium-201 tomograms. Six of nine patients without gastric erosions had positive tomograms. The sensitivity, specificity, and positive and negative predictive values of DT 201 gastric erosions were 100%, 33%, 33%, and 100%, respectively.

CONCLUSIONS

Dipyridamole thallium-201 tomographic imaging has good sensitivity (100%) in detecting esophagogastric mucosal erosions, but its poor specificity (33-57%) results in an unacceptable accuracy as a screening test. Additionally, the cost of radiopharmaceuticals requires that sensitivity and specificity be at least equal to that of endoscopy for this test to be clinically valuable as a screening test. However, a noninvasive test for these diseases is inherently appealing, and further research in this area seems to be warranted.

Involvement of 5-hydroxytryptamine (5-HT)3 receptor mechanisms in regulation of basal pancreatic secretion in conscious rats

The effects of 5-hydroxytryptamine (5-HT)3 receptor antagonists (azasetron and granisetron) on basal pancreatic exocrine secretion were examined in conscious rats. Rats were prepared with cannulae draining bile and pancreatic juice separately. Intravenous injection of azasetron significantly increased pancreatic fluid and protein outputs in a dose-dependent manner. These increases were completely abolished by treatment with atropine, but not affected by bilateral truncal vagotomy. Intravenous injection of granisetron also increased pancreatic secretion, significantly. Intragastric injection of azasetron increased pancreatic secretion, although a double dose was required to elicit the stimulatory effect compared with intravenous injection. It is concluded that 5-HT3 receptor activity is involved in regulation of basal pancreatic secretion in conscious rats.

EM523L, a nonpeptide motilin agonist, stimulates gastric emptying and pancreatic polypeptide secretion

We investigated the efficacy and the mechanism of action of EM523L, a nonpeptide motilin agonist (motilide), on the stimulation of gastric emptying and on the release of gut peptides after ingestion of a solid meat in normal controls (n = 8) and in diabetic patients (n = 8) with signs of neuropathy. A dose of 2 mg EM523L was administered IV over 15 min just after ingestion of a solid meal (200 kcal Gastric emptying was measured by a radionuclide technique. EM523L accelerated gastric emptying and markedly augmented postprandial pancreatic polypeptide (PP) response in both normal control and diabetic patients. This may suggest the mediation of the Vagal-cholinergic pathway to accelerate gastric emptying. The present study offers a promising therapeutic potential of the motilide in gastrointestinal motility disorders like those observed in diabetics mellitus.