Effects of octreotide, a somatostatin analogue, on gastric function evaluated by real-time ultrasonography

Gastrointestinal hormones and regulation of gastric emptying

PURPOSE OF REVIEW

In this review, we evaluate recent findings related to the association between gastrointestinal hormones and regulation of gastric emptying.

RECENT FINDINGS

Motilin and ghrelin, which act during fasting, promote gastric motility, whereas most of the hormones secreted after a meal inhibit gastric motility. Serotonin has different progastric or antigastric motility effects depending on the receptor subtype. Serotonin receptor agonists have been used clinically to treat dyspepsia symptoms but other hormone receptor agonists or antagonists are still under development. Glucagon-like peptide 1 agonists, which have gastric motility and appetite-suppressing effects are used as a treatment for obesity and diabetes.

SUMMARY

Gastrointestinal hormones play an important role in the regulation of gastric motility. Various drugs have been developed to treat delayed gastric emptying by targeting gastrointestinal hormones or their receptors but few have been commercialized.

The inhibitory effect of somatostatin on gastric motility in Suncus murinus

Gastric contractions show two specific patterns in many species, migrating motor contractions (MMC) and postprandial contractions (PPCs), that occur in the fasted and fed states, respectively. In this study, we examined the role of somatostatin (SST) in gastric motility both in vivo and in vitro using the Asian house shrew (Suncus murinus). We performed in vivo recordings of gastric motility and in vitro organ bath experiments using S. murinus, which was recently established as a small laboratory animal for use in tests of gastrointestinal motility. SST (1.65 µg kg⁻¹ min⁻¹) was intravenously administered during phase II of MMC and PPCs. Next, the effect of SST on motilin-induced gastric contractions at phase I of MMC was measured. Cyclosomatostatin (CSST), an SST receptor antagonist, was administered at the peak of phase III of MMC. In addition, the effect of SST (10⁻¹¹–10⁻⁹ M) on motilin-induced gastric contractions was evaluated using an organ bath experiment in vitro. In conscious, free-moving S. murinus, the administration of SST decreased the occurrence of the spontaneous phase II of MMC and PPCs. Pretreatment with SST and octreotide suppressed the induction of motilin-induced gastric contractions both in vivo and in vitro. Administration of CSST before the peak of spontaneous phase III contractions had no effect on gastric contractions. Endogenous SST is not involved in the regulation of gastric MMC and PPCs, but exogenous SST suppresses spontaneous gastric contractions. Thus, SST would be good for treating abnormal gastrointestinal motility disorders.

Use of scintigraphy to evaluate gastric accommodation and emptying: comparison with barostat

BACKGROUND AND AIM

Scintigraphy is a useful noninvasive technique for assessment of gastric motility, especially emptying, but there is little knowledge of use of the technique to assess gastric accommodation. Therefore, to clarify the usefulness of scintigraphy as a technique for assessing gastric accommodation, we compared scintigraphy with barostat, the gold standard modality.

METHODS

Twenty healthy volunteers (14 men, six women; mean age, 28.5 ± 5.4 years) were enrolled in the study. The volunteers ingested a radiolabeled ((99m) Tc) test meal and scintigraphic images were recorded. Radioactivity in the upper third and whole stomach was calculated to evaluate accommodation. In the barostat procedure, gastric accommodation was evaluated by measuring the maximum volume of the distended balloon. Thereafter, correlation between scintigraphic and barostat accommodation was investigated. Intra-and inter-observer variation of the scintigraphic test results were also assessed. Finally, the diagnostic performance of scintigraphy was evaluated by using sumatriptan as a positive control.

RESULTS

Measurements of accommodation by scintigraphy and barostat correlated (r = 0.524, P < 0.05). Sumatriptan significantly increased scintigraphically measured gastric accommodation (with sumatriptan, 51.5 ± 16.4%; without sumatriptan, 38.4 ± 13.8%) (P < 0.01), and had significantly (P < 0.05) delayed 50% half emptying time at 60, 90, 120, and 150 min after the start of the experiment. The data from repeated scintigraphic tests were highly reproducible (r = 0.804) with significant differences not observed among the investigators (inter-observer variation = 0.932, intra-observer variation = 0.898).

CONCLUSION

Gastric scintigraphy is a useful technique for assessing gastric accommodation and emptying.

Therapeutic efficacy of acotiamide in patients with functional dyspepsia based on enhanced postprandial gastric accommodation and emptying: randomized controlled study evaluation by real-time ultrasonography

BACKGROUND

Improvement in subjective symptoms has been reported in functional dyspepsia (FD) patients administered with acotiamide. Improvement was confirmed in meal-related symptoms, such as postprandial fullness, upper abdominal bloating, and early satiety. We examined the mechanism underlying the effects of acotiamide on gastric accommodation reflex (GAR) and gastroduodenal motility in FD patients.

METHODS

Thirty-four FD patients (mean age, 40.4 years) were examined ultrasonographically before and after 14-18 days of acotiamide (100 mg t.i.d.) or placebo administration. To assess GAR, expansion rate in cross-sectional area of the proximal stomach was measured after every 100-mL ingestion, using a straw, of up to 400 mL of a liquid meal (consommé soup, 13.1 kcal; 400 mL) in a supine position. Next, we measured gastric emptying rate (GER), motility index (MI, antral contractions), and reflux index (RI, duodenogastric reflux) to assess gastroduodenal motility. Patients also completed a survey based on the seven-point Likert scale both before and after drug administration.

KEY RESULTS

Of the 37 cases, 19 and 18 were administered with acotiamide and placebo A respectively, significant difference was observed in GAR between the acotiamide and placebo groups (21.7%vs 4.4%) after 400 mL ingestion. GER significantly accelerated after treatment in the acotiamide group (P = 0.012), no significant differences were observed in MI and RI between the two groups. Improvement rates were 35.3 and 11.8% for the acotiamide and placebo groups.

CONCLUSIONS & INFERENCES

Acotiamide significantly enhances GAR and GER in FD patients. Acotiamide may have therapeutic potential for FD patients.

Efficacy of mosapride citrate in proximal gastric accommodation and gastrointestinal motility in healthy volunteers: a double-blind placebo-controlled ultrasonographic study

BACKGROUND

Mosapride citrate, a 5-hydroxytryptamine-4 receptor agonist, enhances antral contractions and gastric emptying, but its effects on proximal gastric accommodation and gastroduodenal motility have not been fully studied. The aim of the present study was to clarify the effects of mosapride citrate on proximal gastric accommodation and gastroduodenal motility in healthy volunteers, using ultrasonography.

METHODS

Fourteen healthy volunteers (mean age 25.3 years) were treated for 14 days with mosapride citrate (15 mg b.d.) or a placebo in a double-blind randomized fashion. Before and after drug treatment, ultrasonographic assessment of gastroduodenal motility was performed. For assessment of the gastric accommodation reflex, the cross-sectional area of the proximal stomach was measured after the incremental ingestion, with a straw, of up to 400 ml of a liquid meal (consommé soup: 13.1 kcal, 400 ml); this was done with the subject in a supine position. Gastric emptying, antral contractions, and the duodenogastric reflux were observed as described previously.

RESULTS

In the subjects treated with mosapride citrate, the expansion rate of the cross-sectional area of the proximal stomach was significantly greater after the ingestion of 400 ml as compared to that of the subjects treated with the placebo. Similarly, gastric emptying and antral contractions increased significantly in the mosapride citrate group as compared to the placebo group. Although the duodenogastric reflux tended to decrease in the mosapride citrate group, it showed no significant difference between the two groups.

CONCLUSIONS

This study shows that mosapride citrate enhances the meal-induced gastric accommodation reflex and promotes adequate gastroduodenal coordination and motility in healthy volunteers.

Efficacy of Rikkunshito, a traditional Japanese medicine (Kampo), in treating functional dyspepsia

BACKGROUND

Rikkunshito, a traditional Japanese (Kampo) medicine, is widely prescribed as an oral preparation for the treatment of functional dyspepsia (FD). In our previous study, we reported that extracorporeal ultrasonography (US) is a useful technique for the assessment of the gastric accommodation reflex (AR) and duodenogastric motility. In this study, we examined the effects of Rikkunshito on the gastroduodenal function in patients with FD.

METHODS

Sixteen FD patients (median age, 45 y) underwent US, before and after 14 days of treatment with Rikkunshito (7.5 g b.d.). For assessment of the AR, a cross-sectional area of the proximal stomach was measured after incremental ingestion of a liquid meal up to 400-mL. The expansion rate was used as the parameter to determine the AR. Then, the gastric emptying rate (GER), motility index (MI), and reflux index (RI) were evaluated using previously reported methods.

RESULTS

Although no significant changes were observed in the total score of the Gastrointestinal Symptom Rating Scale (GSRS), the scores of 3 of the 15 symptoms of GSRS decreased significantly after treatment with Rikkunshito. The expansion rate of the proximal stomach was significantly greater after treatment with Rikkunshito than before the treatment. Although the GER and MI increased significantly, no significant differences in the RI were observed after treatment with Rikkunshito.

CONCLUSION

These observations suggested that Rikkunshito may be beneficial for the treatment of FD patients with impaired AR and gastric motility. These results also suggested that Rikkunshito has a therapeutic potential for FD and GERD.

Relation between histologic gastritis and gastric motility in Japanese patients with functional dyspepsia: evaluation by transabdominal ultrasonography

BACKGROUND

Whether mucosal inflammation affects gastric motility in patients with functional dyspepsia (FD) is controversial. Few reports discuss gastric motility in relation to histologic gastritis. We examined the relation between gastric motility and histologic gastritis in Japanese patients with FD.

METHODS

Subjects were 198 patients examined by ultrasonography (US) and endoscopic biopsy. Histologic gastritis scores were compared to three US gastric motility indices: the motility index (MI), gastroduodenal reflux index (RI), and gastric emptying rate (GER). In cases of gastritis with a high inflammation score (score 2-3), the macrophages in biopsy specimens were counted and compared to the motility indices.

RESULTS

Of the 198 patients, 159 were Helicobacter pylori positive. Comparison of 39 age-and sex-matched H. pylori-positive and 39 H. pylori-negative patients showed that the MI was lower in H. pylori-positive patients (6.78+/-2.17 vs. 7.63+/-2.35, P<0.05), and the RI was higher (5.64+/-4.70 vs. 2.13+/-2.58, P<0.01). Among H. pylori-positive patients, US revealed a decreased MI in patients with a high inflammation score (score 2-3) in the antrum compared with the MI of those with a low inflammation score (score 0-1) (6.52+/-2.38 vs. 7.82+/-1.89, P<0.01). The number of macrophages was not associated with motility indices in patients with a high inflammation score.

CONCLUSION

Histologic gastritis with severe inflammation may inhibit gastric motility.

The use of electrogastrography and external ultrasonography to evaluate gastric motility in Crohn's disease

Although Crohn's disease is associated with various digestive symptoms, there have been few reports on gastric motility. In this study, we conducted a study of gastric motility in Crohn's disease using 20 healthy subjects (N group) and 15 patients with Crohn's disease (C group) by electrogastrography (EGG) using a Nipro electrogastrograph. An EGG was recorded for 30 minutes in a fasting state and after ingestion of 300 ml of a liquid meal. As an index of gastric emptying, the rate of change in the cross-sectional area of the gastric antrum was measured 1 and 15 minutes after ingestion of the liquid meal by external ultrasonography. In an EGG frequency analysis, waveforms with a peak of 3 cycles/minute (cpm) were noted in the N group, and the peak amplitude increased significantly after the ingestion of food. In the C group, division of the normal-gastria component was noted after the ingestion of food in 5 patients (33.3%). In a comparison of the peak amplitudes of fasting brady-gastria, normal-gastria, and tachy-gastria between the N and C groups, the peak amplitude was significantly increased in normal-gastria in the N group, and in brady-gastria and tachy-gastria in the C group. In a comparison of the rates of food ingestion-induced changes in the peak amplitudes for brady-gastria, normal-gastria, and tachy-gastria between the N and C groups, the peak amplitudes were significantly increased in normal-gastria in the N group, but not in the C group. In the case of gastric emptying investigated by external ultrasonography, the rate of food ingestion-induced change in the cross-sectional antrum area was significantly lower in the C group (50.5+/-9.2%) than in the N group (65.0+/-8.5%). For gastrointestinal motility, a 3 cpm normal-gastria represents efficient gastric motility. In the C group, the peak amplitudes of brady-gastria and tachy-gastria were significantly increased, but were low in normal-gastria in the fasting EGG, postprandial division of the normal-gastria component was noted, and the rate of food ingestion-induced increase in the normal-gastria peak amplitude was significantly lower than that in the N group, suggesting that patients with Crohn's disease have a functional abnormality in, not only the small and large intestine, but also the stomach.

Concomitant variations of gastric tone and duodenal motility in humans: results of a placebo-controlled study assessing octreotide and sumatriptan

OBJECTIVE

To describe the concomitant effects of octreotide and sumatriptan on fundic tone and duodenal phase III activity.

MATERIAL AND METHODS

A double-blind study was performed in nine volunteers, studied for 2 h after receiving 50 microg octreotide, 6 mg sumatriptan or placebo. Fundic tone variations were assessed by barostat while antroduodenal motility was studied concomitantly using manometry.

RESULTS

A rapid increase in intrabag volume was observed in all but one subject after both sumatriptan and octreotide administration, while only two subjects exhibited a volume variation after placebo, p<0.01. A significant decrease in the number of phasic contractions was observed after octreotide, while sumatriptan reduced only wave amplitudes (p<0.05). A total of 13 concomitant duodenal phase III-like activities were observed in the duodenum after octreotide, 3 after sumatriptan and 4 after placebo, all followed by spontaneous fundic relaxation with disappearance of phasic contractions, p<0.05. Spontaneous phase III activities were different from phases III-like activities after octreotide in velocity and duration (p<0.05).

CONCLUSIONS

Octreotide induced concomitant fundic relaxation, disappearance of phasic contractions and duodenal phase III-like activity. Sumatriptan relaxed the proximal stomach and reduced the amplitude of fundic phasic contractions without affecting concomitant antroduodenal phase III activity.

Evaluation of the effects of mastication and swallowing on gastric motility using electrogastrography

OBJECTIVES

The influence of mastication and swallowing on gastric motor function was evaluated by electrogastrography (EGG) and abdominal ultrasonography.

METHODS

The subjects were 30 elderly patients with tubal feeding without mastication and swallowing (T group) and 30 elderly controls who processed food by mastication and swallowing (C group). Gastric motor function was percutaneously examined before and after the ingestion of 250 ml of a liquid diet using an electrogastrograph (NIPRO EGG, A and D, Tokyo, Japan). The cross-sectional area of the gastric antrum was measured at 1 and 30 min after the start of ingestion of the liquid diet by external ultrasonography of the abdomen, and the gastric excretion function was evaluated. Furthermore, the spectral analysis of heart rate variability was performed using Holter electrocardiograms before and after ingestion. The low frequency power (LF power, 0.04-0.15 Hz), high frequency power (HF power, 0.15-0.40 Hz), and the LF/HF ratio were determined.

RESULTS

The peak amplitude at 3 cycles per minute (cpm) was significantly increased after ingestion in the C and T groups (p<0.05), and the ratio of increase was significantly lower in the T group (p<0.05). The mean amplitude for the brady-gastria and tachy-gastria was significantly higher in the T group than in the C group (p<0.05). The gastric excretion function, as evaluated by external ultrasonography of the abdomen, was significantly lower in the T group than in the C group (p<0.05). An analysis of heart rate variability demonstrated that the HF power, a parameter of parasympathetic activity, after ingestion was significantly higher in the C group than in the T group (p<0.05). No changes in LF power or LF/HF ratio, parameters of sympathetic activity, were induced by ingestion in either the C or T groups.

CONCLUSIONS

The parasympathetic nerve dominantly controls gastric motor function, but autonomic nervous activity is reduced in patients who are unable to masticate and swallow food, resulting in adverse effects on gastric motor function and excretion function. Mastication and swallowing not only prepare food for passage from the oral cavity to the esophagus but are also important in terms of subsequent events that occur in stomach. It has been proposed that autonomic nervous activity might be involved in mastication and swallowing.

Real-time ultrasonographic assessment of antroduodenal motility after ingestion of solid and liquid meals by patients with functional dyspepsia

BACKGROUND AND AIMS

Although antroduodenal motility has usually been studied by using manometric or scintigraphic methods, ultrasonography is an established, non-invasive method to evaluate duodenogastric motility. We used ultrasonography to evaluate gastric motility in patients with functional dyspepsia.

METHODS

Sixty-four patients with functional dyspepsia and 36 asymptomatic healthy subjects were given liquid and solid test meals. We investigated the gastric emptying rate, motility index, and duodenogastric reflux for the liquid meal and gastric emptying time, half-emptying time, and motility index for the solid meal.

RESULTS

After the liquid meal, the gastric emptying rate and motility index were significantly lower and the duodenogastric reflux was significantly higher in functional dyspepsia patients than in healthy subjects. After the solid meal, gastric emptying time, half-emptying time and the motility index were significantly lower in the patients than in the healthy subjects. Delayed gastric emptying of both meals occurred in only 20.3% of patients. Delayed emptying of the liquid or solid meal occurred in 62.5% of patients. In both groups, gastric emptying time of the solid meal was positively correlated with the motility index at 15 min post-ingestion.

CONCLUSION

In functional dyspepsia patients, delayed gastric emptying of a solid meal was related to antral hypomotility during the early postprandial phase. Ultrasonographic assessment of gastric motility in both liquid and solid meals may provide a better understanding of the pathogenesis of functional dyspepsia.

Dual effects of somatostatin analog octreotide on gastric emptying during and after intragastric fill

The effect of the somatostatin analog agonist octreotide (Oct) on gastric emptying of 12.5% glucose during and after intragastric fill was examined in nondeprived rats equipped with stainless steel gastric fistulas. The rate of intragastric infusion (1.0 ml/min) and the volumes delivered (6 or 12 ml) were within the ranges typically observed in rats normally ingesting the same stimulus. In experiment 1, a dose-related suppression of glucose emptying during 12-min infusions was obtained in response to Oct (0, 0.0014, 0.014, 0.14, and 1.4 nmol/kg sc) injected 60 min before the test. The highest dose tested yielded a 37% suppression of glucose solute emptying during fill. In experiment 2, the suppression of emptying during fill induced by Oct (1.4 nmol/kg) was reversed by 10 or 40 microgram/kg of the somatostatin antagonist cyclo(7-aminoheptanoyl-Phe-D-Trp-Lys-Thr[Bzl]). The antagonist did not by itself affect emptying. Experiment 3 showed that the suppression of emptying obtained with 0.14 and 1.4 nmol/kg Oct had disappeared when the gastric sample was withdrawn 36 min after the termination of 12-min glucose infusions. Experiment 4 showed that the Oct-induced reductions in emptying during 6- and 12-min infusions, in fact, were reversed within 6 min after infusion offset. The point of transition between suppressed and increased emptying did not depend on time from injection or from infusion onset but was linked to the offset of the intragastric infusion regardless of its duration. The present findings support the notion that separable mechanisms govern gastric emptying during vs. after gastric fill.

Effects of somatostatin on proximal gastric motor function and visceral perception

BACKGROUND

Somatostatin affects gastrointestinal motility and secretion and visceral sensation, but little is known about its effects on the proximal stomach.

AIM

To evaluate the effects of somatostatin on proximal gastric motor function and perception of symptoms.

METHODS

Six healthy subjects participated in two experiments performed in random order during continuous intravenous infusion of saline or somatostatin (250 microg/h). Proximal gastric motor function was evaluated using a barostat. We performed pressure and volume distensions and a barostat procedure (minimal distending pressure + 2 mmHg). Symptoms were evaluated at regular intervals using visual analogue scales (VAS).

RESULTS

Neither minimal distending pressure nor gastric fundal tone were significantly different between somatostatin and saline. Pressure-volume curves during distensions were not influenced by somatostatin. However, phasic volume waves were significantly (P < 0.001) reduced by somatostatin, and somatostatin significantly (P < 0.05) reduced symptom perception of fullness and abdominal pressure during stepwise distensions.

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.