Inhibitory effects of cholecystokinin on postprandial gastric myoelectrical activity

Characteristics of Intestinal Myoelectrical and Motor Activities in Diet-Induced Obese Rats: Obesity and Motility

BACKGROUND

Gastrointestinal motility has been reported to be altered in obesity. However, it is unknown whether intestinal myoelectrical activity (IMA) is also changed in obesity.

AIMS

The aim of this study was to characterize intestinal myoelectrical and motility activities in the fasting state, during feeding, and postprandial state after various test meals in diet-induced obese (DIO) rats in comparison with regular rats.

METHODS

IMA was recorded in the fasting, feeding, and postprandial states in DIO and regular rats. Regular laboratory chow, high-fat solid food, and high-fat liquid food were used to test IMA responses to different meals.

RESULTS

(1) The intestinal slow waves in the DIO rats were not different from those in normal rats in the fasting or postprandial state. Neither intestinal transit nor the number of intestinal contractions per minute was altered in DIO rats although gastric emptying was accelerated. (2) Both DIO rats and normal rats showed altered IMA during the first minute of feeding (cephalic stimulation). (3) The intestinal slow waves in both DIO rats and regular rats were impaired slightly but significantly after intake of a high-fat meal.

CONCLUSIONS

Our study demonstrates that intestinal myoelectrical activity is not altered in DIO rats and its postprandial responses to various meals are not altered either. High-fat meals induce intestinal dysrhythmia but do not have a chronic impact on intestinal slow waves in DIO rats.

The effect of drugs and stimulants on gastric myoelectrical activity

Electrogastrography (EGG) is a non-invasive diagnostic method useful for the registration and analysis of gastric myoelectrical activity. Abnormalities within an electrogastrogram were found to correlate with a number of disorders and symptoms, like functional dyspepsia, diabetic gastroparesis and terminal hepatic or renal failure. The EGG is also a valuable diagnostic method enabling the evaluation of the effect of drugs on gastric myoelectrical activity, which can be intentional, as in the case of prokinetics, or can have an adverse character. Our review focuses on drugs with a proven impact on gastric myoelectrical activity and hence on the electrogastrogram. The paper assembles and discusses the results of investigations dealing with changes in the electrogastrograms evoked by various drugs. Moreover, the mechanisms of the influence on the gastric myoelectrical activity of drugs, curative substances and stimulants are presented.

Current status of multichannel electrogastrography and examples of its use

Electrogastrography (EGG) is a non-invasive diagnostic motility for recording gastric myoelectrical activity. Gastric myoelectrical activity was first recorded in 1922. Advances in recording equipment enabled widespread use of cutaneous EGG after 1985. Later, introduction of multichannel EGG (M-EGG) enabled measurement of electrical activity transmission. At present, M-EGG findings are used as objective indicators of gastric motility disorders caused by various diseases. EGG measures two categories of gastric electrical activity: electrical response activity, or spike potentials; and electrical control activity, or slow waves. The appearance of abnormal rhythmic electrical activity is indicative of abnormalities in gastric motility. The normal frequency range of gastric electrical activity (normogastria) is around 3 cycles per min. Multiple EGG parameters assist in the assessment of gastric myoelectrical activity, and significant correlations between EGG and other gastric motility tests have been demonstrated in many studies. In Japan, however, EGG remains in the exploratory stage, and its clinical use is limited. There are large variations in procedures and systems used in previous studies, thus there is a need for standardization of EGG procedures and technical terminology. Here, we outline the current status of EGG and report the M-EGG procedures used in our department in addition to our M-EGG findings.

The abstract of this manuscript was presented during an educational seminar titled "Current status of gastrointestinal motility tests and keys for immediate implementation" at the 54th Annual Meeting of the Japan Society of Smooth Muscle Research

Predictors of gastric myoelectrical activity in type 2 diabetes mellitus

BACKGROUND

Previous studies have clearly demonstrated the delayed gastric emptying of solid meals in diabetics, whereas their gastric myoelectrical activity, which primarily determines gastric motility, has not yet been fully confirmed.

GOALS

This study aimed to clarify the characteristics and potential predictors of gastric myoelectrical activity in type 2 diabetics.

STUDY

Twenty-eight diabetics and 18 healthy controls participated. Duodenal biopsy sample was used for reverse transcription-polymerase chain reaction to evaluate cholecystokinin and motilin mRNA contents. Electrogastrography was performed before and after the test meal, and was assessed in terms of dominant frequency; dominant frequency instability coefficient; and the percentage of bradygastria, normogastria, and tachygastria.

RESULTS

Over the entire recording period, dominant frequency was significantly lower, and dominant frequency instability coefficient and the percentage of bradygastria were significantly higher in diabetics than in controls. In diabetics, the multiple regression analysis demonstrated that dominant frequency instability coefficient and the percentage of tachygastria in the fasting period were dependent on fasting plasma glucose level and HbA1c, respectively. Moreover, dominant frequency over the entire period and the postprandial percentage of bradygastria were significantly associated with body mass index; the fasting percentage of bradygastria and postprandial dominant frequency instability coefficient were associated with fasting serum leptin level; the postprandial percentage of bradygastria was also associated with cholecystokinin mRNA content.

CONCLUSIONS

Gastric myoelectrical activity in type 2 diabetics is impaired on dominant frequency, dominant frequency instability coefficient, and the percentage of bradygastria and predicted by body mass index, fasting serum leptin level, and cholecystokinin mRNA content besides the glycemic status.

Clinical utility of electrogastrography and the water load test in patients with upper gastrointestinal symptoms

We assessed gastric myoelectric functioning in patients with various gastrointestinal symptoms and to determine the utility of electrogastrography in differentiating specific disease entities. Electrogastrography with a water load was performed in 101 patients with reflux disease, 55 patients with active gastric ulcer, 59 patients with functional dyspepsia, and 30 controls. Upper gastrointestinal symptoms were assessed in each patient. Electrogastrography was abnormal in 41 (40.6%) patients with reflux disease, 31 (56.4%) patients with active gastric ulcer, and 26 (44.1%) patients with functional dyspepsia (P=NS). Water load tolerance was greater in controls than any patient group (all P<0.05). Symptoms predicted abnormal electrogastrography in reflux patents with satiety (OR=2.9; P<0.05) and in dyspeptic patients with nausea (OR=3.1; P<0.05). Although electrogastrography is helpful in differentiating subgroups of patients with nausea or satiety, it cannot directly differentiate disease states such as reflux disease, gastric ulcer, and functional dyspepsia.

Role of cholecystokinin and central serotonergic receptors in functional dyspepsia

Symptoms of functional dyspepsia are characterized by upper abdominal discomfort or pain, early satiety, postprandial fullness, bloating, nausea and vomiting. It is a chronic disorder, with symptoms more than 3 mo per year, and no evidence of organic diseases. Dysfunctional motility, altered visceral sensation, and psychosocial factors have all been identified as major pathophysiological mechanisms. It is believed that these pathophysiological mechanisms interact to produce the observed symptoms. Dyspepsia has been categorized into three subgroups based on dominant symptoms. Dysmotility-like dyspepsia describes a subgroup of patients whose symptom complex is usually related to a gastric sensorimotor dysfunction. The brain-gut peptide cholecystokinin (CCK) and serotonin (5-HT) share certain physiological effects. Both have been shown to decrease gastric emptying and affect satiety. Furthermore the CCK induced anorexia depended on serotonergic functions probably acting via central pathways. We believe that abnormalities of central serotonergic receptors functioning together with a hyper responsiveness to CCK or their interactions may be responsible for the genesis of symptoms in functional dyspepsia (FD).

Impaired gastric myoelectricity in patients with chronic pancreatitis: Role of maldigestion

AIM: To investigate whether gastric myoelectrical activity was impaired in patients with chronic pancreatitis (CP) and to explore the role of pancreatic enzyme in regulating gastric myoelectrical activity.

METHODS: Twenty CP patients and 20 controls participated in the study. Gastric myoelectrical activity was recorded by a homemade electrogastrography (EGG) device. Two experiments were carried out. In experiment one, EGG was recorded in both controls and CP patients. While in experiment two, either pancreatic enzymes or placebo was given together with test meals. Spectral analysis was used to generate various EGG parameters.

RESULTS: The control subjects, but not the CP patients, showed typically increased postprandial dominant frequency. The postprandial dominant power (DP) increment (2.24±1.13 vs 5.35±0.96 dB, P = 0.04) and the percentage of normal 2-4 cpm slow waves (63.0±3.8% vs 77.4 ±3.1%, P<0.05) were lower in CP patients when compared with the control. In the 20 CP patients, the DP increment (4.76±1.02 vs 2.53±1.20 dB, P<0.05) and the postprandial percentage of normal 2-4 cpm (74.4±2.8% vs 64.8 ±5.7%, P<0.05) were significantly higher with pancreatic enzyme replacement than the placebo.

CONCLUSION: CP patients have an abnormal postprandial stomach myoelectricity showing poor response in dominant frequency/power and regularity, whereas these abnormalities are corrected after pancreatic enzyme replacement. Maldigestion is likely to be the factor leading to abnormal postprandial gastric myoelectricity of CP patients.

Effects of electroacupuncture on gastric myoelectrical activity in healthy humans

The acupuncture point of the wrists (PC6) and the lower legs (ST36) are common points for the treatment of gastric symptoms. However, it remains unclear whether these two acupoints have different effects on gastric myoelectrical activity. We compared the effect of electroacupuncture (EAP) between PC6 and ST36 on gastric myoelectrical activity using surface electrogastrography (EGG). EAP (1 Hz, for 30 min) was applied at either ST36, or PC6, or both acupoints in eight healthy volunteers. EAP at both PC6 and ST36 did not change the percentage of normal slow waves and tachygastria. While EAP at either PC6 or ST36 did not change period dominant frequency (PDF), EAP at both PC6 and ST36 significantly decreased PDF to 78.1 +/- 8.4% of baselines. EAP at PC6 reduced period dominant power (PDP) to 47.2 +/- 5.3% of baselines, while EAP at ST36 increased PDP to 153.6 +/- 28.3% of baselines. EAP at shoulders (sham acupuncture) did not affect the gastric myoelectrical activity. EAP at either PC6 or ST36 shows an opposite effect on PDP, whereas EAP at both PC6 and ST36 has a synergistic effect on PDF. Understanding site-specific effects of acupuncture may contribute to the selection of appropriate acupoints for treating functional GI disorders.

Dose-related effects of motilin on proximal gastrointestinal motility

AIM

To assess non-invasively the dose-response relations for the effects of exogenous motilin on antrum contraction frequency, gall-bladder volume and gastric myoelectrical activity.

METHODS

In a double-blind, randomized, placebo-controlled, five-way crossover study, 10 fasted healthy volunteers were infused intravenously with synthetic human motilin (0.5, 1, 2 and 4 pmol x min/kg) or placebo for 60 min. Gall-bladder volume and antrum contractions were assessed by ultrasonography and gastric myoelectrical activity by electrogastrography. Motilin concentrations were measured using a radioimmunoassay.

RESULTS

Baseline plasma motilin levels (60 pmol/L) were similar for all treatments. Motilin levels increased upon the start of infusion and rapidly returned to baseline after cessation of the infusion. At motilin doses of 2 and 4 pmol.min/kg, the antrum contraction frequency was significantly augmented, with maximum differences of two contractions per 2-min interval compared to placebo, while no changes in gastric myoelectrical activity were observed. Changes in gall-bladder volume were not significantly different for any of the motilin doses compared to placebo.

CONCLUSIONS

Motilin increased antrum contraction frequency, whereas no effect on gastric myoelectrical activity was observed. Antrum contraction frequency appears to be a useful biomarker for motilin efficacy, and motilin doses of 2 and 4 pmol x min/kg were equally effective.

Gastric dysrhythmia in uremic patients on maintenance hemodialysis

BACKGROUND

Dyspeptic symptoms are common in uremic patients receiving hemodialysis. Investigators have placed emphasis on the changes in histopathology and physiology of the gastrointestinal tract. But not much data about the gastric myoelectric activity are available. The aim of this study was to assess gastric myoelectric activity in uremic patients undergoing hemodialysis.

METHODS

Fifty-eight subjects were enrolled. They were assigned to: group I, uremic patients undergoing hemodialysis with dyspeptic complaints (n = 20); group II, non-uremic patients with matched dyspeptic complaints (n = 20); and group III, healthy volunteers without dyspeptic complaints (n = 18). Gastric myoelectric activity was measured with abdominal surface electrodes in each person. Patients in group I were measured twice, before (group Ia) and after (group Ib) hemodialysis. The data were compared between the groups.

RESULTS

In the prehemodialysis period there was a significantly lower percentage of normal slow-wave frequency when compared with group III (fasting, 66.54%+/-5.39% versus 84.58%+/-3.63%; P < 0.005; fed, 72.25%+/-4.16% versus 89.06%+/-2.57%; P < 0.01). In the post-hemodialysis period the difference was even more profound (fasting, 46.52%+/-4.26% versus 84.58%+/-3.63%; P < 0.001; fed, 51.49%+/-6.89% versus 89.06%+/-2.57%; P < 0.005). Yet, when compared with group II, a significant difference existed only in the post-hemodialysis period (fasting, 46.52%+/-4.26% versus 67.30%+/-3.46%; P<0.001; fed, 51.49%+/-6.89% versus 70.41%+/-4.39%; P < 0.01). Another finding is that hemodialysis decreased the gastric myoelectric activity after hemodialysis (fasting, 66.54%+/-5.39% versus 46.52%+/-4.26%; P < 0.001; fed, 72.25%+/-4.16% versus 51.49%+/-6.89%; P < 0.005).

CONCLUSIONS

Uremic patients undergoing hemodialysis have impaired gastric myoelectric activity. Interestingly, hemodialysis seems to cause deterioration in gastric myoelectric activity.

Effect of lintitript, a new CCK-A receptor antagonist, on gastric emptying of a solid-liquid meal in humans

The role of cholecystokinin (CCK) in the regulation of gastric emptying of physiological meals containing solids and liquids in humans remains controversial. We studied the role of endogenous CCK in the emptying of a solid/liquid meal administering the new, highly specific and potent CCK-A receptor antagonist lintitript. Gastric emptying was assessed in nine healthy male volunteers using a randomized, double blind, two-period crossover design with oral lintitript (15 mg 1 h prior to meal intake) or placebo on two different days. After ingestion of a pancake (570 kcal) labelled with 500 microCi of 99mTc-sulfur colloid and 500 ml 10% dextrose containing 80 microCi. 111In-DTPA, subjects were studied in a sitting position, using a dual-headed gamma camera. Plasma CCK and pancreatic polypeptide (PP) were measured by a specific RIA. Lintitript distinctly accelerated gastric emptying of solids, while gastric emptying of liquids was not significantly altered. The lag period was shortened by 20% (P<0.05), AUC and half emptying time of solid emptying were lowered by 12% and 13%, respectively (P<0.03). Lintitript markedly increased postprandial plasma CCK release (P<0.001) while distinctly reducing postprandial PP levels (P<0.01) as compared to placebo. These data provide further evidence for a significant role of CCK in the regulation of gastric emptying of solids. The study demonstrates for the first time the marked gastrokinetic properties of the new CCK-A receptor antagonist lintitript in humans.

Abnormal gastric myoelectrical activity and delayed gastric emptying in patients with symptoms suggestive of gastroparesis

Gastric myoelectrical activity modulates gastric motor activity. Abnormalities in gastric myoelectrical activity may be associated with gastric motility disorders. The aim of this study was to investigate the correlation of gastric myoelectrical activity with gastric emptying in symptomatic patients with and without gastroparesis. Ninety-seven patients with symptoms suggestive of gastroparesis participated in the study. Gastric myoelectrical activity was recorded using surface electrogastrography. The electrogastrogram (EGG) was recorded for 30 min in the fasting state and for 120 min after a solid test meal. Gastric emptying of the solid meal was simultaneously monitored for 120 min. Patients with delayed gastric emptying showed a significantly lower percentage of normal gastric slow waves (P < 0.03) and a significantly reduced increase of the dominant power in the postprandial EGG (P < 0.02). Postprandial EGG parameters were found to be able to predict delayed emptying of the stomach. Postprandial gastric dysrhythmia predicts delayed gastric emptying with an accuracy of 78%, while the abnormality in postprandial EGG power predicts delayed gastric emptying with an accuracy of 75%. All patients with abnormalities in both the rhythmicity and the power had delayed gastric emptying. Patients with delayed gastric emptying have a lower percentage of normal gastric slow waves in the EGG and a lower postprandial increase in the dominant power. Abnormalities in the postprandial EGG seem to be able to predict delayed emptying of the stomach. However, a normal EGG does not seem to guarantee normal emptying of the stomach.