Effect of cholecystokinin on lower oesophageal sphincter pressure and transient lower oesophageal sphincter relaxations in humans

The Role of a Plant-Only (Vegan) Diet in Gastroesophageal Reflux Disease: Online Survey of the Italian General Population

The relationship between food and the pathophysiological mechanisms of gastroesophageal reflux disease (GERD) is unclear. There are few data on the impact of dietary habits on GERD symptoms and on the incidence of GERD in subjects undergoing plant-based diets. In this study, we investigated the association between diet and GERD, using data collected through an online survey of the Italian general population. In total, 1077 subjects participated in the study. GERD was defined according to the Montreal Consensus. For all subjects age, gender, body mass index (BMI), marital status, education, occupation, alcohol consumption, and smoking habits were recorded. All participants also completed the SF-36 questionnaire on Quality of Life. A total of 402 subjects (37.3%) were vegans and 675 (62.7%) non-vegans. The prevalence of GERD in the total population was 9%. Subjects with GERD-related symptoms recorded a worse quality of life according to SF-36 analysis (p < 0.05 for all dimensions). In multivariate analysis, after adjusting for confounders, participants undergoing a vegan diet had a significantly lower risk of GERD (OR = 0.47, 95% CI 0.28-0.81, p = 0.006). These findings should be taken into account to inform the lifestyle management of GERD.

Non-surgical animal model of gastroesophageal reflux disease by overeating induced in mice

Previous animal models of gastroesophageal reflux disease (GERD) were not physiological and required a variety of surgical procedures. Therefore, the animal model developed by conditions that are similar to the pathogenesis of GERD is necessary. The aim is to establish a non-surgical animal model with GERD caused by overeating induced in mice. To induce mice to overeat, we designed dietary control protocols including repetitive fasting and feeding. The esophageal tissues were evaluated with GERD markers to prove the establishment of a GERD animal model. Mice fasted every other day (group 2) showed more pronounced overeating feature and demonstrated evident changes similar to the macroscopic and microscopic findings of GERD, the expressions of inducible nitric oxide synthase and substance P were stronger. The higher frequency of fasting and overeating could cause GERD effectively. The dietary control can make mice overeat, which elicits the change of lower esophageal mucosa similar to GERD. Thus, the overeating-induced mouse may be used as a GERD mouse model.

Food and Gastroesophageal Reflux Disease

Gastroesophageal reflux disease is a chronic condition with a high prevalence in western countries. Transient lower esophageal sphincter relaxation episodes and a decreased lower esophageal sphincter pressure are the main mechanisms involved. Currently used drugs are efficient on reflux symptoms, but only as long as they are administered, because they do not modify the reflux barrier. Certain nutrients or foods are generally considered to increase the frequency of gastroesophageal reflux symptoms, therefore physicians recommend changes in diet and some patients avoid bothering foods. This review summarizes current knowledge regarding food and gastroesophageal reflux. For example, fat intake increases the perception of reflux symptoms. Regular coffee and chocolate induce gastroesophageal reflux and increase the lower esophageal exposure to acid. Spicy foods might induce heartburn, but the exact mechanism is not known. Beer and wine induce gastroesophageal reflux, mainly in the first hour after intake. For other foods, like fried food or carbonated beverages data on gastroesophageal reflux is scarce. Similarly, there are few data about the type of diet and gastroesophageal reflux. Mediterranean diet and a very low carbohydrate diet protect against reflux. Regarding diet-related practices, consistent data showed that a "short-meal-to-sleep interval" favors reflux episodes, therefore some authors recommend that dinner should be at least four hours before bedtime. All these recommendations should consider patient's weight, because several meta-analyses showed a positive association between increased body mass index and gastroesophageal reflux disease.

Heartburn-Related Internet Searches and Trends of Interest across Six Western Countries: A Four-Year Retrospective Analysis Using Google Ads Keyword Planner

The internet is becoming the main source of health-related information. We aimed to investigate data regarding heartburn-related searches made by Google users from Australia, Canada, Germany, Poland, the United Kingdom, and the United States. We retrospectively analyzed data from Google Ads Keywords Planner. We extracted search volumes of keywords associated with “heartburn” for June 2015 to May 2019. The data were generated in the respective primary language. The number of searches per 1000 Google-user years was as follows: 177.4 (Australia), 178.1 (Canada), 123.8 (Germany), 199.7 (Poland), 152.5 (United Kingdom), and 194.5 (United States). The users were particularly interested in treatment (19.0 to 41.3%), diet (4.8 to 10.7%), symptoms (2.6 to 13.1%), and causes (3.7 to 10.0%). In all countries except Germany, the number of heartburn-related queries significantly increased over the analyzed period. For Canada, Germany, Poland, and the United Kingdom, query numbers were significantly lowest in summer; there was no significant seasonal trend for Australia and the United States. The number of heartburn-related queries has increased over the past four years, and a seasonal pattern may exist in certain regions. The trends in heartburn-related searches may reflect the scale of the complaint, and should be verified through future epidemiological studies.

Cholecystokinin induces esophageal longitudinal muscle contraction and transient lower esophageal sphincter relaxation in healthy humans

Cholecystokinin (CCK) is known to cause lower esophageal sphincter (LES) relaxation through the activation of inhibitory motor neurons. CCK receptor agonists increase the frequency of transient LES relaxation through a peripheral mechanism. Recent studies show that the longitudinal muscle contraction (LMC)-related axial stretch might play a role in the LES relaxation by activating the mechanosensitive inhibitory motor neurons. The aim of our study was to determine whether the CCK-induced LES relaxation and the characteristics of LMC resemble those seen with spontaneous transient LES relaxation in humans. Nine healthy volunteers (5 Fr, 40 ± 12 yr) received escalating doses of CCK-octapeptide (CCK-8) (5, 10, 20, and 40 ng/kg). All subjects demonstrated a monophasic response to 5 ng/kg of CCK-8. In the majority of subjects, this response consisted of partial LES relaxation. All subjects showed a biphasic response to 40 ng/kg of CCK-8. The latter in most subjects consisted of 1) a period of partial relaxation followed by 2) complete LES relaxation along with crural diaphragm inhibition. The length of the esophagus decreased by 0.9 ± 0.4 cm, and muscle thickness increased by 40 ± 14% to 1.4 ± 0.2 mm ( P < 0.05) during initial partial LES relaxation. During complete LES relaxation there was greater LMC, as demonstrated by an esophageal shortening of 1.9 ± 0.5 cm and an increase in muscle thickness of 100 ± 16% ( P < 0.01). The complete phase 2 LES relaxation typically terminated with a robust after-contraction. Atropine significantly attenuated the CCK-induced esophageal LMC, prevented crural diaphragm inhibition, and abolished the phase 2 complete LES relaxation. NEW & NOTEWORTHY The phenotypic features of CCK-induced longitudinal muscle contraction (LMC), complete lower esophageal sphincter (LES) relaxation, and crural diaphragm inhibition, followed by a robust after-contraction, resemble those seen during spontaneous transient LES relaxation. A strong temporal relationship between the LMC and complete transient LES relaxation supports our hypothesis that the LMC plays an important role in the LES relaxation and crural diaphragmatic inhibition.

Vegetal and Animal Food Proteins Have a Different Impact in the First Postprandial Hour of Impedance-pH Analysis in Patients with Heartburn

Background and Aims

By means of 24 h impedance-pH monitoring, we aimed to evaluate the effect of two different meals with a bromatological balanced composition: one with a prevailing component of animal proteins and the other with vegetable proteins.

Patients and Methods

We enrolled 165 patients with heartburn and negative endoscopy, who underwent impedance-pH monitoring off therapy. Patients were allocated to receive a Mediterranean diet with a total caloric intake of about 1694 kcal, divided into two meals: one with a prevailing component of animal proteins and the other with vegetable proteins. We evaluated the total reflux number, acid exposure time (AET), and symptom-reflux association with impedance-pH analysis. Moreover, during the first postprandial hour (at lunch and dinner), we evaluated the total reflux number, number of acid and weakly acidic refluxes, AET, and presence of symptoms.

Results

The male/female ratio was 80/85. Mean age was 51.9 ± 12.1 years. Impedance-pH analysis showed that 55/165 patients had pathological AET or a number of refluxes (nonerosive reflux disease (NERD)), 49/165 had normal AET and a number of refluxes but positive symptom-reflux association (hypersensitive esophagus (HE)), and 61/165 had normal AET and a number of refluxes with negative symptom-reflux association (functional heartburn (FH)). The overall first postprandial hour analysis showed a higher total reflux number, acid reflux number, and AET after the animal protein meal than after the vegetable protein meal. Moreover, more symptoms were reported after the animal protein meal. Similar results have been observed in the three different subcategories of patients (NERD, HE, and FH).

Conclusions

Vegetable proteins are associated with a lower number of refluxes, particularly acid refluxes, and with a reduced number of symptoms during the first postprandial hour. This is a pilot study and future investigations are warranted to confirm these results.

The effects of intraduodenal nutrient infusion on serum CCK, LES pressure, and gastroesophageal reflux

BACKGROUND

Fats cause reflux symptoms in many patients and cholecystokinin (CCK) may play a role. This study was designed to evaluate the effects of intraduodenal nutrient infusion on serum CCK levels, lower esophageal sphincter (LES) pressure, and gastroesophageal reflux (GER).

METHODS

Twenty-four asymptomatic volunteers were studied. A Dent sleeve catheter assessed LES function while an impedance-pH catheter measured reflux events. Participants were randomized to fat (F), carbohydrate (C) or protein (P) infusion. Serum CCK and LES pressures were measured at baseline and after nutrient infusion.

KEY RESULTS

Baseline LES pressures and CCK levels were similar in all three groups. A significant linear decrease was found in LES pressure during F, but not C or P, infusion (P=0.004). A significant interaction effect was noted between the infusion groups and CCK levels (P=0.002). A significant linear increase was noted in CCK levels during F but not during C or P infusion (P=0.02). A significant inverse correlation was found between CCK levels and LES pressure (ρ=-0.43; P=0.04). Esophageal acid exposure was significantly increased in the F infusion group (median; interquartile range: 1.10%; 0.25-4.7%) compared to both the C (0.03%; 0.00-0.39%) and P infusion (0.03%; 0.00-0.39%) groups (P=0.04).

CONCLUSIONS & INFERENCES

Intraduodenal F infusion was associated with an increase in CCK levels, while P and C were not. LES pressure decreased significantly after fat infusion and reflux events were more frequent. Fat-induced CCK release is another mechanism that contributes to GER.

Does impaired gallbladder function contribute to the development of Barrett's esophagus and esophageal adenocarcinoma?

INTRODUCTION

Esophageal adenocarcinoma is aetiologically associated with gastro-esophageal reflux, but the mechanisms responsible for the metaplasia-dysplasia sequence are unknown. Bile components are implicated. Impaired gallbladder function may contribute to duodenogastric reflux (DGR) and harmful GERD.

AIMS

This study aims to compare gallbladder function in patients with Barrett's esophagus, adenocarcinoma, and controls.

METHODS

Three groups of patients, all free of gallstone disease, were studied. Group 1: (n = 15) were normal controls. Group 2: (n = 15) were patients with >3-cm-long segment of Barrett's esophagus. Group 3: (n = 15) were patients with esophageal adenocarcinoma. Using real-time ultrasonography unit, gallbladder volume was measured in subjects following a 10-h fast. Ejection fraction was calculated before and after standard liquid meal and compared between the groups.

RESULTS

The mean percentage reduction in gallbladder volume was 50% at 40 min in the adenocarcinoma group compared with 72.4% in the control group (p < 0.001). At 60 min, gallbladder filling had recommenced in the control group to 64.1% of fasting volume while continuing to empty with further reduction to 63% in the Barrett's group and to 50.6% (p = 0.008) in the adenocarcinoma group. The mean gallbladder ejection fraction decreased progressively from controls to Barrett's to adenocarcinoma and was significantly lower in Barrett's group (60.9%; p = 0.019) and adenocarcinoma group (47.9%; p < 0.001) compared with normal controls (70.9%).

CONCLUSION

Gallbladder function is progressively impaired in Barrett's esophagus and adenocarcinoma. Gallbladder malfunction increases duodenogastric reflux, exposing the lower esophagus to an altered chemical milieu which, in turn, may have a role in promoting metaplasia-dysplasia-neoplasia sequence in the lower esophageal mucosa.

Review article: the clinical relevance of transient lower oesophageal sphincter relaxations in gastro-oesophageal reflux disease

BACKGROUND

Transient lower oesophageal sphincter relaxations (TLOSR) are considered the physiological mechanism that enables venting of gas from the stomach and appear as sphincter relaxations that are not induced by swallowing. It has become increasingly clear that most reflux episodes occur during TLOSRs and therefore play a key role in gastro-oesophageal reflux disease (GERD).

AIM

To describe the current knowledge about TLOSRs and its clinical implications.

METHODS

Search of the literature published in English using the PubMed database and relevant abstracts presented at international conventions.

RESULTS

Several factors influence the rate of TLOSRs including anti-reflux surgery, meal, body position, nutrition, lifestyle and a wide array of neurotransmitters. Ongoing insights in the neurotransmitters responsible for the modulation of TLOSRs, as well as the neural pathways involved in TLOSR induction, have lead to novel therapeutic targets. These therapeutic targets can serve as an add-on therapy in patients with an unsatisfactory response to proton pump inhibitor by inhibiting TLOSRs and its associated reflux events. However, the TLOSR-inhibiting drugs that are currently available still have significant side effects.

CONCLUSION

It is likely that in the future, selected GERD patients may benefit from transient lower oesophageal sphincter relaxation inhibition when compounds are found without significant side effects.

Seasonal variation in the incidence of gastroesophageal reflux disease

BACKGROUND

To examine the seasonal variation in the incidence of gastroesophageal reflux disease (GERD) for different gender and age groups and its association with climatic parameters (ambient temperature, relative humidity, atmospheric pressure, rainfall, and hours of sunshine).

METHODS

A total of 76,636 ambulatory care visits for the treatment of GERD between 2001 and 2006 were included. Monthly GERD incidence rates per 10,000 people were calculated over 72 months and categorized by gender and age groupings (19-44, 45-64, and >or=65 years). Seasonality is a general component of time-series patterns. The auto-regressive integrated moving average (ARIMA) regression method was used to evaluate the effects of climatic and monthly factors on GERD incidence rates after adjusting for the time-trend effect.

RESULTS

Seasonal trends showed an incidence peak in October to December, followed by a sharp decrease in January, and a trough in February; a fairly similar seasonal pattern of GERD incidence was apparent for gender, age, and combined groups. The ARIMA test for seasonality found a significant association for the total group (P < 0.01), for female (P < 0.05) patients, and for the 45 to 64 years (P < 0.01) and >64 years (P < 0.01) age groups. The ARIMA models also showed that relative humidity was negatively related to monthly GERD incidence rates for men (P < 0.01) and the >64 years (P < 0.01) age group.

CONCLUSION

Data showed seasonal variations in GERD incidence. Relative humidity was associated with monthly GERD incidence rates for men and the >64 years age group.

The impact of lifestyle modification on the health-related quality of life of patients with reflux esophagitis receiving treatment with a proton pump inhibitor

OBJECTIVES

Although lifestyle modification involving diet, exercise, cessation of smoking, etc. is generally advised for patients with reflux esophagitis (RE), few data that show its clinical benefits are available. We analyzed whether lifestyle modification improves health-related quality of life (HRQOL) in Japanese patients with RE receiving the proton pump inhibitor (PPI) lansoprazole as a post hoc analysis of an observational study that investigated the effect of lansoprazole on HRQOL.

METHODS

Patients with RE received lansoprazole for 8 weeks. HRQOL was assessed using the 8-Item Short-Form Health Survey (SF-8) and RE-specific HRQOL questionnaires at baseline and after 4 and 8 weeks of treatment. Physical and mental component summaries (PCS, MCS) and RE-specific summary (RES) scores were calculated.

RESULTS

Of the 8,757 patients analyzed, 40.8% were advised regarding new lifestyle at the start of lansoprazole treatment (Group A), 33.3% were advised to continue the lifestyle as advised previously (Group B), and 25.9% did not receive any advice (Group C). The change in PCS from baseline at week 8 for Group A was 5.7 +/- 8.1, and this was significantly greater (P < 0.001) than the increases achieved in Groups B (4.3 +/- 7.5) and C (4.0 +/- 7.6). The changes in MCS and RES were also significantly greater in Group A than in the other groups. The changes in HRQOL scores from baseline were significantly greater in Group A than in the other groups, irrespective of baseline patient characteristics.

CONCLUSIONS

Lifestyle modification may be clinically beneficial in terms of improving HRQOL in Japanese patients with RE who are receiving treatment with a PPI.

Evaluation of surgical outcomes and gallbladder characteristics in patients with biliary dyskinesia

INTRODUCTION

This study was designed to compare symptomatic outcomes following cholecystectomy in patients with biliary dyskinesia.

MATERIALS AND METHODS

From 1999 to 2006 at New York University Medical Center, 197 adults underwent hepatobiliary scintigraphy with cholecystokinin administration to evaluate gallbladder ejection fraction (GBEF). Biliary dyskinesia was demonstrated in 120 patients based on decreased GBEF of </=35%. Forty-four patients underwent cholecystectomy, and data from chart review and telephone questionnaires were available for 42 patients. Patients reported symptomatic improvement whether gallstones were present (25/27, 92.6%) or absent (13/15, 86.7%) prior to cholecystectomy (p = 0.90). The most common pathologic findings were chronic cholecystitis and cholesterolosis, regardless of the presence of gallstones. Additional data from 101 of the 120 patients with decreased GBEF demonstrated 74/101 (73.2%) patients were diagnosed with gastroesophageal reflux disease (GERD), and 59/101 (58.4%) patients were diagnosed with gastritis.

RESULTS

The results of this study suggest that biliary dyskinesia should be considered as part of the spectrum of symptomatic gallbladder disease that can be successfully treated with cholecystectomy and that biliary dyskinesia is associated with GERD and gastritis.

Risk factors of gastroesophageal reflux disease in Shiraz, southern Iran

AIM: To determine the prevalence and symptoms of gastroesophageal reflux disease (GERD) in a healthy general population in relation to demographic, lifestyle and health-seeking behaviors in Shiraz, southern Iran.

METHODS: A total of 1978 subjects aged > 35 years who referred to Gastroenterohepatology Research Center and who completed a questionnaire consisting of 27 questions for GERD in relation to demographic, lifestyle and health-seeking behaviors were included in this study for a period of five months. The validity and reliability of the questionnaire were determined.

RESULTS: The prevalence of GERD was 15.4%, which was higher in females (17.3%), in rural areas (19.8%), and in illiterate subjects (21.5%) and those with a mean age of 50.25 years. The prevalence was significantly lower in subjects having fried food (14.8%), and fruit and vegetables (14.6%). More symptoms were noticed in subjects consuming pickles (22.1%), taking aspirin (21%) and in subjects with psychological distresses (27.2%) and headaches (22%). The correlation was statistically significant between GERD and halitosis (18.3%), dyspepsia (30.6%), anxiety (19.5%), nightmares (23.9%) and restlessness (18.5%). Their health seeking behavior showed that there was a significant restriction of diet (20%), consumption of herbal medicine (19%), using over-the-counter drugs (29.9%) and consulting with physicians (24.8%). Presence of GERD symptoms was also significantly related to a previous family history of the disease (22.3%).

CONCLUSION: GERD is more common in females, rural and illiterate subjects and correlated with consumption of pickles, occurrence of headache, psychological distress, dyspepsia, halitosis, anxiety, nightmare and restlessness, and a family history of GERD and aspirin intake, but the correlation was negative with consumption of fat and fiber intake.

Erosive esophagitis in the Philippines: a comparison between two time periods

BACKGROUND

In Asia, the incidence of gastroesophageal reflux disease diagnosed through endoscopy has increased from 3-9% to 14-16% in the last decade. The aim of this study was to determine the prevalence of erosive esophagitis (EE) over a span of 10 years in a tertiary care facility in the Philippines.

METHODS

All patients diagnosed with EE from 1994 to 1997 (period A) and from 2000 to 2003 (period B) were included in the study. The modified Savary-Miller and Los Angeles classifications were used to grade EE for periods A and B, respectively.

RESULTS

A total of 15 981 upper endoscopies were evaluated for this study. There was no significant difference in the male: female ratio (period A 1.43:1 vs period B 1.25:1, P = 0.459) and in the mean age of patients with EE (period A 46.4 vs period B 47.5, P = 0.395). The prevalence of EE was significantly higher (P < 0.0001) in period B (6.3%) as compared to period A (2.9%). However, despite a higher prevalence, more patients had mild esophagitis in period B as compared to period A. Conversely, there were more patients with esophageal ulcers (18.6%vs 5.9%, P < 0.001), esophageal strictures (2.3%vs 0%, P = 0.003), and hiatal hernia (15.8%vs 7.5%, P = 0.001) in period A. The presence of concomitant Barrett's esophagus was not significantly different between the two time periods (period A 3.2%vs period B 5%, P = 0.367).

CONCLUSIONS

The prevalence of EE was higher in 2000-2003 than in 1994-1997, although the complications associated with the disease diminished. The prevalence of concomitant Barrett's esophagus remained stable.

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.

A very low-carbohydrate diet improves gastroesophageal reflux and its symptoms

Obese patients with gastroesophageal reflux disease (GERD) may experience resolution of symptoms utilizing a very low-carbohydrate diet. The mechanism of this improvement is unknown. This studied aimed to prospectively assess changes in distal esophageal acid exposure and GERD symptoms among obese adults initiating a very low-carbohydrate diet. We studied obese individuals with GERD initiating a diet containing less than 20 g/day of carbohydrates. Symptom severity was assessed using the GERD Symptom Assessment Scale--Distress Subscale (GSAS-ds). Participants underwent 24-hr esophageal pH probe testing and initiated the diet upon its completion. Within 6 days, a second pH probe test was performed. Outcomes included changes in the Johnson-DeMeester score, percentage total time with a pH<4 in the distal esophagus, and GSAS-ds scores. Eight participants were enrolled. Mean Johnson-DeMeester score decreased from 34.7 to 14.0 (P=0.023). Percentage time with pH<4 decreased from 5.1% to 2.5% (P=0.022). Mean GSAS-ds score decreased from 1.28 to 0.72 (P=0.0004). These data suggest that a very low-carbohydrate diet in obese individuals with GERD significantly reduces distal esophageal acid exposure and improves symptoms.

Effect of caffeine on lower esophageal sphincter pressure in Thai healthy volunteers

Caffeine affects many aspects of body function including the gastrointestinal system. A single-blinded experimental study was performed to evaluate the effect of caffeine on lower esophageal sphincter (LES) and esophageal peristaltic contractions in healthy Thai adults. The volunteers were six men and six women aged 19-31 years. Subjects drank 100 mL of water. Five wet swallows were performed 30 min after the drink. The basal LES pressure was continuously measured using esophageal manometric technique. They then consumed another 100 mL of water containing caffeine at the dose of 3.5 mg/kg body weight. The swallows and basal LES pressure monitoring were repeated. The results showed no change in basal LES pressure after a water drink while caffeine consumption significantly lowered the pressure at 10, 15, 20 and 25 min. The mean amplitude of contractions and peristaltic velocity were decreased at the distal esophagus at 3 and 8 cm above LES. The mean duration of contraction was decreased at the distal part but increased at the more proximal esophagus. The heart rate, systolic and diastolic blood pressures were increased significantly at 10-20 min after caffeine ingestion. This study indicated that caffeine 3.5 mg/kg affected esophageal function, resulting in a decrease in basal LES pressure and distal esophageal contraction, which is known to promote the reflux of gastric contents up into the esophagus.

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.

Review article: treatment for gastro-oesophageal reflux disease--lifestyle advice and medication

Management of gastro-oesophageal reflux disease (GERD) is aimed at reducing oesophageal acid exposure to achieve symptom relief. Therapy has traditionally included advice to the patient on diet and lifestyle management. Recent evidence suggests, however, that some specific dietary modifications may be applicable to the Japanese patient. For example, ingestion of Japanese sweet cakes or rice cakes should be avoided by the Japanese patient with GERD as these foods may provoke heartburn. Pharmacological therapy is, however, usually also required for effective symptom relief. While antacids and histamine H(2)-receptor antagonists have a role in treating mild GERD, effective relief of many cases of oesophagitis is usually only achieved by using proton-pump inhibitors such as lansoprazole, omeprazole and rabeprazole. In the Japanese population, variation in the genetic polymorphism of CYP2C19 (a cytochrome P450 isoenzyme) leads to considerable inter-individual unpredictability in the activity of lansoprazole and omeprazole due to inter-individual differences in the extent to which these agents are metabolized. Consequently, rabeprazole, which does not undergo hepatic biotransformation by CYP2C19, offers significant advantages over the other PPIs as a result of its more predictable activity. This, coupled with its more rapid onset of action, leads to a more efficient and less variable acid-suppressing effect.

Effect of oral CCK-1 agonist GI181771X on fasting and postprandial gastric functions in healthy volunteers

CCK influences satiation and gastric and gallbladder emptying. GI181771X is a novel oral CCK-1 agonist; its effects on gastric emptying of solids, accommodation, and postprandial symptoms are unclear. Effects of four dose levels of the oral CCK-1 agonist GI181771X and placebo on gastric functions and postprandial symptoms were compared in 61 healthy men and women in a randomized, gender-stratified, double-blind, double-dummy placebo-controlled, parallel group study. Effects of 0.1, 0.5, and 1.5 mg of oral solution and a 5.0-mg tablet of GI181771X on gastric emptying of solids by scintigraphy, gastric volume by (99m)Tc-single photon emission computed tomographic imaging, maximum tolerated volume of Ensure, and postprandial nausea, bloating, fullness, and pain were studied. On each of 3 study days, participants received their randomly assigned treatment. Adverse effects and safety were monitored. There were overall group effects of GI181771X on gastric emptying (P < 0.01) and fasting and postprandial volumes (P = 0.036 and 0.015, respectively). The 1.5-mg oral solution of GI181771X significantly delayed gastric emptying of solids (P < 0.01) and increased fasting (P = 0.035) gastric volumes without altering postprandial (P = 0.056) gastric volumes or postprandial symptoms relative to placebo. The effect of the 5.0-mg tablet on gastric emptying of solids did not reach significance (P = 0.052). Pharmacokinetic profiles showed the highest area under the curve over 4 h for the 1.5-mg solution and a similar area under the curve for the 0.5-mg solution and 5-mg tablet. Adverse effects were predominantly gastrointestinal and occurred in a minority of participants. GI181771X delays gastric emptying of solids and exhibits an acceptable safety profile in healthy participants. CCK-1 receptors can be modulated to increase fasting gastric volume.

Coordinated gastric and sphincter motility evoked by intravenous CCK-8 as monitored by ultrasonomicrometry in rats

Gastric and sphincter motility evoked by intravenous injection of CCK-8 were investigated in urethane-anesthetized rats. Digital ultrasonomicrometry was used to monitor pyloric (PYL), antral (ANT), corpus (COR), and lower esophageal sphincter (LES) movements while simultaneously measuring intragastric pressure (IGP) and, in some experiments, subdiaphragmatic intraesophageal pressure (sIEP). Intracrystal distances (ICD) were measured continuously between pairs of piezoelectric crystals affixed to the serosa of PYL, ANT, COR (circular and longitudinal), and LES. Consecutive intravenous injections of CCK-8 (0.3, 1, and 3 microg/kg) at 30-min intervals caused dose-dependent simultaneous tonic contractions of PYL and ANT, LES opening, and drops in IGP with peak changes at 3 microg/kg of -17.9 +/- 2.1, -7.7 +/- 2.5, 6.5 +/- 1.4, and -29.2 +/- 3.8%, respectively, whereas intravenous saline had no effect. Rhythmic contractile activity was inhibited by CCK-8. COR responses were not significantly different from vehicle controls for most metrics, and the direction of response for circular COR varied between preparations, although not for repeated trials in a single preparation. During the LES response to CCK-8, sIEP rose in parallel with drops in IGP, indicating formation of a common cavity. Recovery of LES ICD after intravenous CCK occurred more rapidly than recovery of PYL ICD, suggesting the importance of preventing simultaneous patency of gastroesophageal and gastroduodenal passages. The CCK(A) receptor antagonist devazepide (500 microg/kg intravenous) inhibited motion responses evoked by intravenous CCK-8. These data revealed CCK-8-induced gastric and sphincter activity consistent with retropulsion of gastric content.

Effect of bombesin on esophageal motility in humans

We have investigated the effect of bombesin on esophageal motility and explored the mechanism of action of bombesin. Eight healthy subjects were studied in random order during intravenous administration of (1) bombesin, (2) bombesin + vagal cholinergic receptor blockade with atropine and (3) bombesin + somatostatin. Lower esophageal sphincter pressure (LESP) and esophageal body motility were recorded continuously by Dent-sleeve manometry. Bombesin significantly (p < 0.01) increased LESP from 20 +/- 2 mmHg to 43 +/- 6 mmHg. Neither atropine nor somatostatin significantly reduced the bombesin-induced increases in LESP. Bombesin significantly (p<0.05) increased peristaltic wave amplitude (from 61 +/- 4 to 105 +/- 9 mmHg) and duration (from 2.9 +/- 0.2 to 4.8 +/- 0.3 s) in the mid and distal part of the esophagus. Neither atropine nor somatostatin significantly reduced the esophageal body motor response to bombesin. In conclusion (1) bombesin significantly increases LESP and affects esophageal body motility by increasing peristaltic wave amplitude and duration and (2) the effect of bombesin on esophageal motility is not dependent on vagal cholinergic mechanisms and is not mediated by the action of gastrointestinal hormones released by bombesin.

Manometric and pH-metric features in gastro-oesophageal reflux disease patients with and without Helicobacter pylori infection

BACKGROUND

The role of Helicobacter pylori in the pathogenesis and evolution of gastro-oesophageal reflux disease is still debated.

AIM

To investigate the impact of Helicobacter pylori infection on the oesophageal function and on intra-gastric and intra-oesophageal pH in patients with gastro-oesophageal reflux.

METHODS

Fifty patients with non-complicated-gastro-oesophageal reflux disease classified according to Savary-Miller in: grade O, n=24; grade 1, n=19; grade 2, n=6; grade 3, n=1. Of these patients, 24 were Helicobacter pylori positive and 26 negative. Patients underwent, on two different days, stationary oesophageal manometry and 24-hour gastro-oesophageal pH-metry.

RESULTS

No difference was observed between Helicobacter pylori infected and non-infected individuals with regard to lower oesophageal sphincter function, oesophageal peristalsis and gastrooesophageal reflux. These parameters were more impaired in individuals with erosive gastro-oesophageal reflux disease but this result was not dependent on the Helicobacter pylori status. Helicobacter pylori did not influence the pattern of gastric pH; however, considering only individuals with non-erosive gastro-oesophageal reflux disease, gastric pH was significantly higher in infected individuals, who, histologically, also showed a corpus predominant gastritis.

CONCLUSIONS

In patients with gastro-oesophageal reflux disease, Helicobacter pylori does not affect the oesophageal motility or the gastro-oesophageal reflux. These parameters are strictly related to the severity of gastro-oesophageal reflux disease as assessed at endoscopy. In patients with non-erosive gastro-oesophageal reflux disease, a corpus predominant Helicobacter pylori gastritis could be responsible for the less severe gastro-oesophageal reflux.

Gastro-oesophageal reflux disease in Asia

Gastro-oesophageal reflux disease (GORD) occurs more frequently in Europe and North America than in Asia but its prevalence is now increasing in many Asian countries. Many reasons have been given for the lower prevalence of GORD in Asia. Low dietary fat and genetically determined factors, such as body mass index and maximal acid output, may be important. Other dietary factors appear to be less relevant. Increased intake of carbonated drinks or aggravating medicines may influence the increasing rates of GORD in some Asian countries but no strong evidence links other factors, such as the age of the population, smoking or alcohol consumption, to GORD. The management of GORD in Asia is similar to that in Europe and North America but the lower incidence of severe oesophagitis in Asia may alter the approach slightly. Also, because Asians tend to develop stomach cancer at an earlier age, endoscopy is used routinely at an earlier stage of investigation. Gastro-oesophageal reflux disease is essentially a motility disorder, so short-term management of the disease can usually be achieved using prokinetic agents (or histamine (H2)-receptor antagonists). More severe and recurrent GORD may require proton pump inhibitors (PPI) or a combination of prokinetic agents and PPI. The choice of long-term treatment may be influenced by the relative costs of prokinetic agents and PPI.

Control of transient lower esophageal sphincter relaxations and reflux by the GABA(B) agonist baclofen in normal subjects

BACKGROUND & AIMS

Transient lower esophageal sphincter (LES) relaxations are the major mechanism of gastroesophageal reflux in normal subjects and in most patients with reflux disease. gamma-Aminobutyric acid (GABA) is an important inhibitory neurotransmitter within the central nervous system which is present in regions of the brainstem that are believed to mediate transient LES relaxations. The aim of this study was to investigate the effect of a GABA(B) agonist baclofen on postprandial gastroesophageal reflux and transient LES relaxations.

METHODS

In 20 healthy volunteers, esophageal motility and pH were measured, with the subjects in the sitting position, for 3 hours after a 3000-kJ mixed nutrient meal. On separate days at least 1 week apart, 40 mg oral baclofen or placebo was given 90 minutes before the meal.

RESULTS

Baclofen significantly reduced the rate of reflux episodes by more than 60% from 1.0 (0.3-2.7) to 0.3 (0-1.0) per hour (median [interquartile range]). Baclofen also reduced the rate of transient LES relaxations from 5.7 (4.9-7.8) to 2.2 (1.3-3.8) per hour and increased basal LES pressure from 8.7 +/- 1.4 to 10.8 +/- 0.8 mm Hg.

CONCLUSIONS

In normal human subjects, the GABA(B) agonist baclofen significantly inhibits gastroesophageal reflux by inhibition of transient LES relaxations. These findings suggest that GABA(B) agonists may be useful as therapeutic agents for the management of reflux in patients with gastroesophageal reflux disease.

Activation of the GABA(B) receptor inhibits transient lower esophageal sphincter relaxations in dogs

BACKGROUND & AIMS

Transient lower esophageal sphincter relaxation (TLESR) appears to be the most frequent motor event responsible for gastroesophageal reflux. Because TLESRs are considered to be triggered by activation of gastric mechanoreceptors, and because the gamma-aminobutyric acid type B (GABA(B))-receptor agonist baclofen is known to inhibit transmitter release from mechanosensitive afferents, the effects of baclofen on TLESRs in the dog were assessed.

METHODS

A total of 183 recordings of the pharyngeal, esophageal, lower esophageal sphincter, and gastric pressures as well as measurement of esophageal pH were performed in 15 awake dogs. Racemic baclofen, its enantiomers, and the GABA(B)-receptor antagonist CGP36742 were administered before stimulation of TLESRs by a liquid meal and air insufflation. The pharmacodynamics of baclofen were compared with its pharmacokinetics.

RESULTS

Baclofen dose-dependently inhibited TLESRs, with a 50% effective dose (ED(50)) of 1.0 micromol/kg after intravenous administration. The maximal inhibition amounted to approximately 80%. Intragastric baclofen was almost equally effective (ED(50), 1.8 micromol/kg), compatible with the complete oral availability of the drug (100%). The inhibitory effect of baclofen resided in the pharmacologically active R enantiomer, and CGP36742 reduced some of the effects of baclofen.

CONCLUSIONS

Baclofen is a potent and efficacious inhibitor of TLESRs and reflux in the dog. Activation of the GABA(B) receptor may be a new approach to the treatment of reflux disease.

Motor and sensory function of the proximal stomach in reflux disease and after laparoscopic Nissen fundoplication

OBJECTIVE

After Nissen fundoplication, dyspeptic symptoms such as fullness and early satiety develop in >30% of patients. These symptoms may result from alterations in proximal gastric motor and sensory function.

METHODS

We have evaluated proximal gastric motor and sensory function using an electronic barostat in 12 patients after successful laparoscopic Nissen fundoplications (median follow-up; 12 months). Twelve age- and gender-matched patients with severe gastroesophageal reflux disease (GERD) and 12 healthy volunteers served as controls. Studies were performed in the fasting state and after meal ingestion. Gastric emptying tests were performed in all patients. Vagus nerve integrity was measured by the response of pancreatic polypeptide (PP) to insulin hypoglycemia.

RESULTS

Minimal distending pressure and proximal gastric compliance were not significantly different between post-Nissen patients, GERD patients, and healthy controls. Postprandial relaxation of the stomach, however, was significantly (p < 0.05) reduced post-Nissen (267 +/- 34 ml), compared with controls (400 +/- 30 ml) and GERD (448 +/- 30 ml). Postprandial relaxation was significantly (p < 0.01) prolonged in GERD patients. Postprandial relaxation of the stomach correlated with gastric emptying of solids (r = 0.62; p = 0.01). Gastric emptying of solids became significantly (p < 0.05) faster after fundoplication. Postprandial fullness was significantly (p < 0.05) increased in the operated patients.

CONCLUSIONS

Post-Nissen patients have a significantly reduced postprandial gastric relaxation and significantly accelerated gastric emptying, which may explain postoperative dyspeptic symptoms. The abnormalities result from fundoplication and not from vagus nerve injury or reflux per se, because in reflux patients gastric relaxation and gastric emptying are prolonged.

Endogenous cholecystokinin in postprandial lower esophageal sphincter function and fundic tone in humans

Transient lower esophageal sphincter (LES) relaxations (TLESRs) are the main underlying mechanism of gastroesophageal reflux. Although CCK acts through CCK-A receptors to increase the TLESRs induced by gastric distension, the respective roles of endogenous CCK and fundic tone in triggering postprandial TLESRs remain unknown. The aim of this study was to determine the effect of the CCK-A receptor antagonist, loxiglumide, on postprandial LES function and fundic tone in humans. LES motor events and fundic tone were simultaneously monitored in two groups of healthy volunteers. Recordings were performed during fasting and for 3 h after a liquid meal (200 ml/200 kcal) administered either orally or intraduodenally at a rate mimicking gastric emptying. Each subject received loxiglumide (10 mg. kg-1. h-1) or saline (control) in randomized order, which was started 40 min before the meal and maintained for 3 h thereafter. After the oral meal, loxiglumide significantly reduced TLESRs (P = 0.002) without significantly affecting LES pressure and fundic tone. After duodenal infusion of the meal, loxiglumide totally abolished the increase in TLESRs, reduced LES pressure fall (P < 0.02), and strongly inhibited fundic relaxation (P = 0.0001). We concluded that endogenous CCK is involved in the postprandial control of both LES function and fundic tone through activation of CCK-A receptors.

Involvement of cholecystokininA receptors in transient lower esophageal sphincter relaxations triggered by gastric distension

OBJECTIVE

Transient lower esophageal sphincter relaxations (TLESRs) are the main mechanism underlying gastroesophageal reflux. In the present study we evaluated the effect of loxiglumide, a specific cholecystokininA (CCKA)-receptor antagonist, on the occurrence of TLESRs evoked by gastric distension.

METHODS

Eight healthy subjects underwent esophageal manometry using a 10-lumen sleeve assembly during placebo or loxiglumide (10 mg/kg/h) in a randomized double-blind order. Gastric distension was induced by inflation of 400 ml of air.

RESULTS

Basal lower esophageal pressure (LESP) and swallow-induced relaxation were not affected by loxiglumide. Loxiglumide significantly reduced the number of TLESRs, from 11.5 (5.8-18.3) to 6.0 (3.3-14.3) during the total recording period of 1 h, and from 5.5 (4.25-7.5) to 2.0 (0.5-6.8) during the first 15 min. The number of common cavities was significantly decreased by loxiglumide, from 8.0 (4.0-20.0) to 5.0 (2.0-7.8). TLESRs represented the main mechanism (60% during placebo, 74% during loxiglumide) underlying common cavities, followed by swallow-induced relaxation.

CONCLUSIONS

Loxiglumide significantly reduces the number of TLESRs triggered by gastric distension without interfering with swallow-related relaxation of the lower esophageal sphincter, suggesting the involvement of CCKA receptors in the reflex pathway mediating TLESRs.

Neuronal pathways and transmission to the lower esophageal sphincter of the guinea Pig

BACKGROUND & AIMS

The lower esophageal sphincter (LES) normally controls the opening and closing of the gastroesophageal junction to resist gastric reflux but allow swallowing. Neuronal pathways controlling the guinea pig LES were investigated anatomically and physiologically in isolated preparations.

METHODS

Intracellular recording from the LES with focal electrical stimulation and retrograde and anterograde neuronal tracing were used.

RESULTS

Electrical stimulation on the LES evoked inhibitory junction potentials (IJPs), which were reduced by 60% by 100 micromol/L N-nitro-L-arginine and subsequently blocked by 0.5 micromol/L apamin, unmasking excitatory junction potentials, which were abolished by 1 micromol/L hyoscine. Esophageal or vagal stimulation evoked IJPs, which were blocked by 100 micromol/L hexamethonium. Focal stimulation of the upper stomach evoked IJPs at 5-8 of 20 stimulation sites, which were abolished by cutting between the stimulation site and sphincter. Application of 1,1'-didodecyl-3,3,3', 3'-tetramethyl indocarbocyanine perchlorate (DiI) to the gastric sling muscle anterogradely labeled many motor axons in the sling muscle but few in the LES, confirming that the two muscles are separately innervated. DiI on the esophagus labeled nerve fibers, but not cell bodies, in the upper stomach.

CONCLUSIONS

The inhibitory motor neurons of the LES receive inputs from the vagus nerve, esophagus, and upper stomach.

Endogenous cholecystokinin enhances postprandial gastroesophageal reflux in humans through extrasphincteric receptors

BACKGROUND & AIMS

Exogenous cholecystokinin (CCK) decreases lower esophageal sphincter (LES) pressure and increases transient LES relaxations (TLESRs) in humans. The aims of this study were to determine whether endogenous CCK increases gastroesophageal reflux in humans and whether this is a direct effect on the LES.

METHODS

Esophageal pH, LES pressure, and gallbladder volume were measured in 8 healthy volunteers after ingestion of a 181-kcal meal alone or adding 12 g cholestyramine to increase endogenous CCK release. In 7 additional volunteers, the effect of cholestyramine was studied during intravenous perfusion of saline or the CCK-A receptor antagonist loxiglumide. In circular LES strips from 9 transplant donors, we measured the effect of CCK-8 (10(-11) to 3 x 10(-8) mol/L) on basal tension and on electrical field-induced relaxation.

RESULTS

Cholestyramine increased gallbladder emptying, reflux episodes, TLESRs, and time of esophageal pH of <4. Loxiglumide inhibited postprandial gallbladder emptying, reflux episodes, TLESRs, and time of pH of <4 and prevented the decrease in LES pressure induced by cholestyramine. In vitro, CCK-8 contracted LES strips through a tetrodotoxin-insensitive pathway but did not modify electrical field-induced LES relaxations.

CONCLUSIONS

Endogenous CCK enhances postprandial gastroesophageal reflux in humans by increasing the rate of TLESRs and reduces postprandial LES pressure. These actions seem mediated by extrasphincteric CCK-A receptors that override a direct contractile effect of CCK on the LES muscle.

Effect of medium- and long-chain triglycerides on lower esophageal sphincter pressure: role of CCK

Fat meals are known to decrease lower esophageal sphincter (LES) pressure, possibly through postprandial CCK release. Dietary fat consists mainly of long-chain triglycerides (LCT), which potently stimulate CCK secretion. This effect contrasts with that of medium-chain triglycerides (MCT), which do not induce CCK release. We recorded LES pressure and gallbladder volume in six healthy subjects on five separate occasions during intraduodenal administration of 1) saline control, 2) LCT, 3) MCT, 4) LCT during intravenous infusion of the CCK receptor antagonist loxiglumide, and 5) MCT together with loxiglumide. LES pressure decreased significantly during administration of both LCT and MCT. Loxiglumide completely prevented the reduction in LES pressure during intraduodenal LCT, but not during intraduodenal MCT. Gallbladder volume decreased during LCT, but not during MCT. It is concluded that intraduodenal administration of equimolar amounts of both LCT and MCT significantly reduces LES pressure. The effect of LCT on LES pressure is mediated by CCK. The effect of MCT is not dependent on CCK, since MCT does not release CCK and loxiglumide does not prevent the MCT-induced reduction in LES pressure.

Effect of amino acids on lower esophageal sphincter characteristics and gastroesophageal reflux in humans

The effect of a commercially available mixed amino acids solution, when given either intravenously or intragastrically, on lower esophageal sphincter (LES) pressure, frequency of transient LES relaxations (TLESRs) and gastroesophageal reflux (GER) was investigated in six healthy volunteers. LES pressure and esophageal pH were simultaneously recorded on three separate occasions 1 hr before (basal) and 3 hr during intravenous or intragastric infusion of amino acids (250 mg protein/kg/hr) or saline (control). No significant changes in LES pressure were seen in the control experiment. Intravenous amino acids caused a rapid and sustained (P < 0.01) decrease in LES pressure whereas intragastric amino acids decreased LES pressure only gradually and temporarily (P < 0.01). In the three experiments no significant differences were observed in TLESR frequency, the number of GER episodes, the mechanism of reflux, or duration of acid exposure. In healthy subjects both intragastric and, especially, intravenous infusion of amino acids significantly decrease LES pressure but do not affect the frequency of TLESRs or GER episodes during a continuous liquid gastric load.

Mechanisms of gastro-oesophageal reflux in the ferret

Transient lower oesophageal sphincter (LOS) relaxation is the major mechanism of gastro-oesophageal reflux in humans--an event unassociated with swallowing. Mechanisms involved in triggering transient LOS relaxation are poorly understood, and their further study requires a small animal model. In this study we aimed to establish methods for prolonged ambulant oesophageal manometry in ferrets, and to determine motor events associated with reflux episodes and their triggering by different gastric nutrient loads. Forty-two studies were performed on nine ferrets with chronic cervical oesophagostomies, through which a manometric assembly was introduced and secured to a collar, which incorporated a microphone for detection of swallows. The assembly included a gastric feeding channel, one gastric and four oesophageal manometric sideholes, a 2.5-cm-long LOS sleeve sensor, and an oesophageal pH electrode. Intragastric infusions were given over 2 min, the first after a 30-min control recording period, and in 29/42 studies, a second infusion was given 60 min later. Infusions were either 25 mL 10% dextrose solution, pH 3.5 (22 studies), 25 mL triglyceride emulsion (Intralipid) pH 3.5 (11 studies), or 25 mL air (nine studies). Episodes of oesophageal acidification were absent before gastric infusions. After infusion, 2.1 +/- 0.2 episodes occurred over the first 30 min. After glucose infusion, 15/18 acidification episodes (83%) occurred during transient LOS relaxation, and 3/18 (17%) occurred after gradual (< 1 mmHg sec-1) downward drifts in basal LOSP to < 2 mmHg. After lipid infusion two acidification episodes occurred, both during transient LOS relaxation. Mean duration of transient LOS relaxation was 8.0 +/- 0.4 sec. All infusions increased occurrence of transient LOS relaxation to a similar extent, each of which ended with primary peristalsis. We conclude that gastric infusion of glucose, lipid and gas are all effective in provoking gastro-oesophageal reflux in ferrets. Reflux occurs through similar mechanisms to those seen in humans, i.e. increased triggering of transient LOS relaxation. The conscious ferret is therefore an appropriate model for future studies of manipulation of mechanisms giving rise to gastro-oesophageal reflux.

Effect of gastrin-17 on lower esophageal sphincter characteristics in man

We studied the effect of gastrin-17 on lower esophageal sphincter (LES) characteristics in man. Nine healthy volunteers participated in two experiments performed in random order during continuous infusion of saline (control) or gastrin-17 (15 pmol/kg/hr). LES pressure (LESP) and transient lower esophageal sphincter relaxations (TLESR), as most the important reflux mechanism, were measured with intraesophageal sleeve manometry combined with pH metry. Infusion of gastrin-17 resulted in plasma gastrin levels comparable to those reached after a mixed meal. During continuous gastrin infusion, LESP decreased significantly (P < 0.05) compared to control. The rate and duration of TLESR was not influenced by gastrin-17. Gastroesophageal reflux and the number of TLESR associated with reflux were significantly (P < 0.05) increased during gastrin infusion. These results suggest that in humans gastrin at physiological postprandial plasma concentrations decreases LESP, does not influence TLESR, but increases the percentage of TLESR associated with reflux.

Cholecystokinin in transient lower oesophageal sphincter relaxation due to gastric distension in humans

BACKGROUND AND AIMS

Transient lower oesophageal sphincter relaxations (TLOSRs) has been found to be the main mechanism of gastro-oesophageal reflux. In dogs, cholecystokinin (CCK) is involved in their occurrence. The aim was to evaluate the role of endogenous and exogenous CCK in the occurrence of TLOSRs induced by gastric distension at constant pressure in humans.

METHODS

Ten healthy volunteers were studied. Lower oesophageal sphincter pressure was monitored with a sleeve device and gastric distension was performed via an intragastric bag monitored by a barostat. During distensions, saline, CCK (30 ng/kg/h) or the CCK-A receptor antagonist loxiglumide (10 mg/kg/h) was perfused in a random double blind order.

RESULTS

There was no significant difference between the number of TLOSRs during the different distensions with saline; CCK increased the number of TLOSRs at a mean rate of 13.1 compared with 9.1 with saline (p < 0.001). Loxiglumide significantly decreased the number of relaxations to 5.3 versus 8.3 under paired saline infusion (p < 0.001).

CONCLUSIONS

In humans, CCK-A receptor subtype is involved in the occurrence of transient lower oesophageal sphincter relaxations induced by gastric distension.

Relationship between postprandial esophageal acid exposure and meal volume and fat content

The effect of meal volume and fat content on gastroesophageal reflux was investigated in 20 asymptomatic healthy subjects. In each subject, intraesophageal pH monitoring was performed during a 3-hr postprandial period (PP) in the same position (supine or upright) on two successive days. On day 1, 500-ml low- and high-fat meals were ingested and, on day 2, an 800-ml low-fat meal was ingested. The acid exposure time was assessed as the percentage of time with a pH < 4.0. The acid exposure time in subjects in the upright position was significantly longer in the 800-ml group than in the 500-ml group for the entire PP (2.7 +/- 1.5%; mean +/- SE, 0.7 +/- 0.4%; P < 0.05). Of subjects in the supine position, the high-fat group showed significantly longer acid exposure time than the low-fat group both for the entire PP (7.6 +/- 3.0%, 0.7 +/- 0.5%; p < 0.05) and for the second hour (P < 0.05). We have demonstrated that differences in the meal volume and fat content influence gastroesophageal reflux in healthy asymptomatic subjects and that this influence varies with the position.