Gastric motor physiology and pathophysiology

Review article: Pharmacologic management of obesity - updates on approved medications, indications and risks

BACKGROUND

Obesity has reached epidemic proportions, with >40% of the US population affected. Although traditionally managed by lifestyle modification, and less frequently by bariatric therapies, there are significant pharmacological advancements.

AIMS

To conduct a narrative review of the neurohormonal and physiological understanding of weight gain and obesity, and the development, clinical testing, indications, expected clinical outcomes, and associated risks of current FDA-approved and upcoming anti-obesity medications (AOMs).

METHODS

We conducted a comprehensive review in PubMed for articles on pathophysiology and complications of obesity, including terms 'neurohormonal', 'obesity', 'incretin', and 'weight loss'. Next, we searched for clinical trial data of all FDA-approved AOMs, including both the generic and trade names of orlistat, phentermine/topiramate, bupropion/naltrexone, liraglutide, and semaglutide. Additional searches were conducted for tirzepatide and retatrutide - medications expecting regulatory approval. Searches included combinations of terms related to mechanism of action, indications, side effects, risks, and future directions.

RESULTS

We reviewed the pathophysiology of obesity, including specific role of incretins and glucagon. Clinical data supporting the use of various FDA-approved medications for weight loss are presented, including placebo-controlled or, when available, head-to-head trials. Beneficial metabolic effects, including impact on liver disease, adverse effects and risks of medications are discussed, including altered gastrointestinal motility and risk for periprocedural aspiration.

CONCLUSION

AOMs have established efficacy and effectiveness for weight loss even beyond 52 weeks. Further pharmacological options, such as dual and triple incretins, are probable forthcoming additions to clinical practice for combating obesity and its metabolic consequences such as metabolic dysfunction-associated steatotic liver disease.

Factors Determining Effective Probiotic Activity: Evaluation of Survival and Antibacterial Activity of Selected Probiotic Products Using an "In Vitro" Study

There are many different probiotic products on the market. Are they all equally effective? What criteria should a probiotic formulation meet to provide the most benefit to the patient? The current research aims to evaluate the parameters that influence the effectiveness of market probiotic products. These properties are critical for restoring eubiosis in patients with drug-induced dysbiosis or other pathological conditions, which could be caused by stress, wrong eating. Methods: The disintegration time of probiotic capsules in hydrochloric acid was investigated using a disintegration testing device. The survival rate of probiotic preparations in hydrochloric acid at pH 2 and in a 0.4% bile solution was then evaluated. For this purpose, the number of bacteria before and after incubation in the respective solutions was determined using the plate method. Inhibition of gastrointestinal pathogens by the probiotic products was determined using the Strus bar graph method. The highest survival rate of probiotic bacteria at low pH is shown by preparations produced in the form of acid-resistant capsules. Conclusions: The most important factor determining the good survival of bacterial strains under conditions simulating the gastrointestinal tract is the type of capsule used for their production and storage. The best antimicrobial activity against most common human gastrointestinal pathogens such as Eschericha coli, Shigella, Salmonella spp., Clostridioides difficile (the largest inhibition zones) are shown by probiotic products with the greatest diversity of bacterial strains.

EUS-Guided Intragastric Injection of Botulinum Toxin A in the Preoperative Treatment of Super-Obese Patients: a Randomized Clinical Trial

BACKGROUND

Obesity is a disease that is highly prevalent in Brazil, and the associated comorbidities represent a major global public health challenge. Botulinum toxin type A (BTX-A) is a potent neurotoxin and inhibitor of gastric smooth muscle activity. In theory, BTX-A administration should promote early satiety and weight loss because it delays gastric emptying by inhibiting acetylcholine-mediated peristalsis, which is primarily responsible for gastric motility. Because results in the literature are discrepant, the efficacy of intragastric injections of BTX-A as a primary treatment for obesity remains unknown. The objective of this prospective, double-blind, single-center randomized study was to evaluate the effects of endoscopic ultrasound-guided intragastric BTX-A injections, as a bridge to bariatric surgery, in super-obese patients.

METHODS

Thirty-two super-obese patients were randomized to one of two groups: BTX-A, in which 200 units of BTX-A were injected into the gastric antrum and body; and control, in which the same injections were performed with 0.9% saline. Weight, body mass index (BMI), and loss of excess weight were measured monthly over a 6-month period. Gastric emptying scintigraphy was performed before and after the procedure.

RESULTS

The patients in both groups showed significant weight loss over the course of the study (p < 0.001). There were no statistically significant differences between the groups regarding weight loss, excess weight, total loss of excess weight, total weight loss, or change in BMI.

CONCLUSIONS

Intragastric injection of BTX-A does not appear to be an effective method of achieving preoperative weight loss in super-obese patients.

Botulinum Toxin A for Controlling Obesity

Rapid growth of the overweight population and the number of obese individuals in recent decades suggests that current strategies based on diet, exercise, and pharmacological knowledge are not sufficient to address this epidemic. Obesity is the result of a high caloric intake and energy storage, not counterbalanced by an equally important energy expense. Botulinum toxin type A (BoNT-A) use is rapidly expanding to include treatment of a variety of ophthalmological, gastrointestinal, urological, orthopedic, dermatological, secretory, painful, and cosmetic disorders. Many studies evaluating the effect of BoNT-A in gastric antrum e/o fundus for the treatment of obesity have been published. This treatment modality was based on the observation that gastric injection of BoNT-A in laparatomized rats induced a significant reduction of food intake and body weight. These studies have been published yielding debated results. Differences in the selection of patients, the doses of BoNT-A, the method of administration of the toxin, and the instruments of evaluation of some parameters among these studies may be the cause. In this review, it will study the state-of-the-art use of BoNT-A in obesity basic science models and review the clinical evidence on the therapeutic applications of BoNT-A for obesity.

Effects of electrical stimulation at different locations in the central nucleus of amygdala on gastric motility and spike activity

The aim of the study was to determine the effects of electrical stimulation of different locations in the central nucleus of amygdala (CNA) on gastric motility and spike activity in dorsal vagal complex. Gastric motility index (GMI) and firing rate (FR) of dorsal vagal complex neurons were measured in adult Wistar rats respectively. Neuronal spikes in dorsal vagal complex (DVC) were recorded extracellularly with single-barrel glass microelectrodes. Each type of responses elicited by electrical stimulation in medial (CEM) and lateral (CEL) subdivisions of CNA were recorded, respectively. GMI was significantly increased after stimulation of CEM (p<0.01), and significantly decreased in response to CEL stimulation (p<0.01). After stimulation of CEM, FR in medial nucleus of the solitary tract (mNST) decreased by 31.6 % (p<0.01) and that in dorsal motor nucleus of the vagus (DMNV) increased by 27.1 % (p<0.01). On the contrary, FR in mNST increased (p<0.01) and that in DMNV decreased in response to CEL stimulation (p<0.05). In conclusions, our findings indicated that different loci of CNA may mediate differential effects on gastric activity via changes in the firing of brainstem neurons controlling gut activity.

Effects of muscarinic receptor stimulation and nitric oxide synthase inhibition on gastric tone and gastric myoelectrical activity in canines

AIMS

This study was designed to assess whether the muscarinic receptor stimulation and nitric oxide synthase inhibition were equally effective on gastric fundic tone or gastric myoelectrical activity (GMA) in canines, and the correlation between gastric fundic tone and GMA.

METHODS

Gastric fundic tone and GMA were recorded on seven dogs implanted with serosal electrodes and a gastric cannula.

RESULTS

Bethanechol and L-nitro-N-arginine (L-NNA) significantly increased gastric fundic tone; gastric volume was decreased with bethanechol or L-NNA (P < 0.05). Increased spike activities were observed after both bethanechol and L-NNA. The percentage of slow waves superimposed with spikes was increased with bethanechol (P < 0.001) and L-NNA (P < 0.05). There was a significant reduction in dominant frequency (DF) (P < 0.05), dominant power (DP) (P < 0.05) and percentage of normal slow waves (%N) (P < 0.05) with bethanechol, while no significant change was observed with L-NNA. The variation of gastric tone was not correlated with parameters of GMA.

CONCLUSIONS

Muscarinic receptor stimulation and nitric oxide synthase inhibition have similar effects on gastric tone and gastric spike activities, but different effects on gastric slow waves. Gastric fundic tone does not correlate with gastric slow waves.

Radiographic study of patients submitted to total gastrectomy using Safatle reconstruction technique

BACKGROUND

Ever since the first total gastrectomy, there has always been a great concern in increasing the survival of patients, and with the advance of techniques, in improving the quality of life of these patients. The most common reconstruction technique of the gastrointestinal transit is the Roux-en-Y. The reposition of a functional pouch in place of the resected stomach was proposed to minimize the postprandial symptoms, improve the nutritional grade and consequently, the quality of life. The Safatle reconstruction of the gastrointestinal transit technique consists of, in short, in the association of the interposition of the jejunal loop with partial transit through the duodenum, with an inverted Roux-en-Y and with the creation of a pouch which resembles the dynamics of the stomach, achieved by duodenojejunal segment which has an antiperistalsis emptying.

AIM

To assess, by radiographic means, the emptying of the duodenojejunal pouch in patients submitted to total gastrectomy using the Safatle reconstruction technique.

METHOD

Twelve patients submitted to total gastrectomy using the Safatle technique due to gastric cancer were studied. They were summoned to perform contrasted radiographies of the esophagus-duodenum-jejunum by the videofluoroscopic method during the months of July and August, 2005.

RESULTS

All the patients presented satisfactory movement of the duodenojejunal pouch and an adequate emptying in antiperistalsis without food stasis. There has been an average 25-minute drainage time of the duodenojejunal pouch.

CONCLUSION

The duodenojejunal pouch, in the patients submitted to total gastrectomy using the Safatle reconstruction, presented adequate emptying and movement.

Intragastric injection of botulinum toxin A for the treatment of obesity

BACKGROUND

Botulinum toxin A (BTX-A) is a powerful and long-acting inhibitor of muscular contractions in both striated and smooth muscles. Hypothetically, BTX-A should inhibit the acetylcholine-mediated peristalsis, which is mainly responsible for gastric motility, and thereby induce slowed gastric emptying, earlier satiety and weight loss. The aim of this study was to observe the effects of endoscopic intragastric injections of BTX-A in obese patients.

METHODS

After approval by the University Ethics Committee, 10 female patients with class I obesity (body mass index 30-35) were double-blind randomized into 2 groups (BTX-A and 0.9% Saline). In Group 1, 200 U BTX-A were injected endoscopically into the antrum and the distal gastric body. In Group 2, 0.9% saline was injected endoscopically into the antrum and the distal gastric body. Body weight and feeling of satiety were recorded monthly over a period of 6 months.

RESULTS

Both groups (BTX-A and 0.9% Saline) showed no significant weight reduction (P>0.05). One patient in Group 1 and two patients in Group 2 reported a feeling of early satiety. No adverse effects related to BTX-A or complications resulting from the endoscopic procedure were observed.

CONCLUSION

Intragastric injection of BTX-A for the treatment of obesity does not seem to reduce body weight.

Different effects of whole milk and a fermented milk with the same fat and lactose content on gastric emptying and postprandial lipaemia, but not on glycaemic response and appetite

Longitudinal studies indicate that milk and fermented milk products lower basal plasma cholesterol concentrations, despite their high content of saturated fat, and therefore have favourable health effects. However, there have been few studies on the postprandial effects of milk products. The present study compared the effect of whole milk with a fermented milk, A-38, on postprandial carbohydrate and lipid metabolism, gastric emptying and appetite. Eight healthy young men participated. On the two test days, they arrived fasting for collection of baseline values before consuming the meals, which for a 75 kg subject consisted of 1·4 litre milk or fermented milk, plus 165 mg [13C]acetate (for later determination of gastric emptying by a [13C]acetate breath test). Lactose (15 g) was added to the A-38 meal to equalize the lactose content. Postprandially the A-38 meal resulted in a slower gastric emptying rate than milk (P>0·001). Furthermore, the A-38 meal resulted in a greater increase and a quicker decrease of the triacylglycerol content in all lipoprotein fractions (LDL-fraction,P>0·05; other fractions,P>0·001) and of the gastrointestinal hormones (cholecystokinin and peptide YY,P>0·05; gastric inhibitory polypeptide and glucagon-like polypeptide-1,P>0·001). There were no significant differences in appetite sensations (measured by visual analogue scale) or in the glucose and insulin response (P<0·10). The slower emptying rate of the liquid phase after the A-38 meal is probably due to the higher viscosity of A-38. The lower and more prolonged triacylglycerol response after the milk meal might be caused by coagulation of milk in the stomach.

Effect of botulinum toxin antral injection on gastric emptying and weight reduction in obese patients: a pilot study

BACKGROUND

A potential approach to the treatment of morbid obesity is reduction of gastric emptying to achieve satiety. Botulinum toxin A (Btx-A) is a long-acting inhibitor of acetylcholine-mediated peristalsis, which is mainly responsible for gastric motility.

AIM

To investigate whether botulinum toxin A, injected in the antrum of obese patients, delays gastric emptying.

METHODS

In a double_blind study, 18 healthy obese subjects (body mass index >30) were randomized into three groups (BTX133, BTX200 and Saline); they received Btx-A133U, Btx-A200U, or saline under endoscopic control. Gastric emptying was tested by scintigraphy before and 10 days after treatment. Body weight variations and appetite sensation were recorded after 5 weeks.

RESULTS

Fourteen patients completed the study. The botulinum toxin A-treated groups showed weight reduction, which was not statistically significant. The effects on gastric emptying were variable. Most of the botulinum toxin A treated patients reported a reduced appetite.

CONCLUSION

This pilot clinical trial suggests potential activity of botulinum toxin A for the manipulation of appetite.

Botulinum toxin injected in the gastric wall reduces body weight and food intake in rats

BACKGROUND

Botulinum toxin is a powerful, long-acting inhibitor of muscular contractions in both voluntary and smooth muscle. It acts by blocking the release of the neurotransmitter acetylcholine. In the stomach, propulsive contractions of the antrum are necessary for the gastric contents to pass into the duodenum.

AIMS

To investigate whether intramuscular injections of botulinum toxin type A into the gastric antrum of rats would cause a reduction in food intake and hence body weight, by inhibition of gastric emptying.

MATERIALS AND METHODS

This was a prospective, randomized, 3-way parallel group study in rats. The first group was anaesthetized, laparotomized and given 20 U of botulinum toxin type A by intramuscular injection into the gastric antrum (botulinum toxin type A group, n=14). The second group was anaesthetized, laparotomized and injected with saline (sham group, n=14) and the third group did not have any intervention (control group, n=5). Food intake was measured daily for 7 weeks and body weight was measured daily for 10 weeks.

RESULTS

There was a significant difference in loss of body weight between the two treated groups (14.0 +/- 8.2% botulinum toxin type A group, 4.4 +/- 2.7% sham group; P < 0.001). Further, the time to reach the weight nadir was significantly longer in the botulinum toxin type A group (8.7 +/- 3.9 days) compared with the sham group (5.3 +/- 3.8 days; P < 0.04). There were no significant differences between the sham and control groups for any of the body weight parameters. The minimum dietary intake was significantly lower in the botulinum toxin type A group than in the sham group (37.8 +/- 21.8% of the basal value in the botulinum toxin type A group, vs. 65.5 +/- 32.0 in the sham group, P < 0.05). In addition, the time to reach the nadir was significantly prolonged (8.2 +/- 3.5 days, botulinum toxin type A group vs. 4.9 +/- 1.7 days, sham group, P < 0.001).

CONCLUSIONS

The parallel reduction of body weight and food intake in botulinum toxin type A treated animals is consistent with a long lasting inhibition of the antral pump. This is probably due to slowed gastric emptying leading to early satiety. Patients with morbid obesity might benefit from endoscopic injections of botulinum toxin type A into the stomach wall.

Effect of gastric myoelectric activity on carbohydrate absorption of fruit juice in children

Juices have a different rate of gastric emptying than other foods. This may alter the rate of delivery of carbohydrates to the small bowel for absorption. The aim of the study is to demonstrate that faster gastric emptying is associated with greater production of hydrogen through a randomized, crossover study of 39 healthy children. The electrogastrography (indicator of the gastric myoelectric activities) and breath hydrogen tests (indicator of carbohydrate malabsorption) were performed at baseline and after ingestion of 240 to 330 mL of grape or pear juice given in a random order. The cutaneous electrogastrogram was analyzed by running spectral analysis to compute pre- and postprandial period dominant power (PDP) and running spectrum total power (RSTP). Postprandial PDP and RSTP were higher (p < 0.02) in the pear juice group than in the grape juice group, suggesting higher antral myoelectric activities. Twenty three percent of the subjects had significant movement artifacts that suggested discomfort after drinking pear juice compared to 5% after grape juice (p < 0.03). Breath hydrogen test was more frequently positive (increase >20 part per million [ppm] above baseline) after pear juice (52.2%; mean, 36 +/- 33 ppm) than after grape juice (4.3%, 6 +/- 6 ppm). In a multiple regression analysis, the most predictive independent variable of hydrogen concentration was found to be either postprandial PDP (r2 = 0.24; p < 0.002), or RSTP (r2 = 0.37; p < 0.001). Juices affect gastric myoelectric activity. Grape juice induces lower antral myoelectric activities and is better absorbed. The malabsorption of carbohydrates of juices is in part related to their effect on the gastric physiology.

Role of nitric oxide in fasting gastric fundus tone and in 5-HT1 receptor-mediated relaxation of gastric fundus

Fasting gastric fundus tone is maintained by continuous cholinergic input. 5-Hydroxytryptamine-1 (5-HT1) receptor activation decreases gastric fundus tone in humans. Whether this fundus-relaxing effect is mediated via inhibition of cholinergic input or via activation of a nitrergic pathway is unknown. The aim of the present study was to determine the effect of nitrergic inhibition on feline gastric fundus tone and on 5-HT1 receptor-mediated relaxation of the fundus. Administration of Nomega-nitro-L-arginine methyl ester (L-NAME) alone caused a significant decrease of the mean baseline volume (P < 0.005), which was restored completely by addition of L-arginine. Sumatriptan caused a dose-dependent relaxation of the gastric fundus (P < 0.0005). This relaxation was inhibited by L-NAME (P < 0.02) and was restored by prior administration of L-arginine. Buspirone did not cause any change in mean baseline volume, whereas the sumatriptan-induced relaxation was not affected by prior administration of NAN-190. Our data indicate that fasting fundus tone relies not only on continuous cholinergic input but also on continuous nitrergic input, implying that fasting fundus tone is maintained by the balance of a cholinergic and nitrergic drive. Furthermore, fundus relaxation via 5-HT1 receptor activation is mediated through activation of a nitrergic pathway.

In vitro motility disorders associated with displaced abomasum in dairy cows

The objective of this study was to investigate in vitro abomasal motility in dairy cows diagnosed with displaced abomasum. Longitudinal muscle myenteric plexus preparations originating from the abomasal antrum of control cows, and cows diagnosed with left displaced abomasum (LDA), right displaced abomasum (RDA) or abomasal volvulus (AV) were used. In control preparations electrical field stimulation evoked an immediate cholinergic contractile response exceeding amplitude of basal contractions by 60%. In contrast, contractile activity was significantly inhibited during electrical stimulation in LDA, RDA and AV by 47%, 66% and 45%, respectively. This inhibition was reversed in the presence of L-NAME. The staining intensity of NADPH-positive myenteric neurones was significantly higher in displaced abomasa than in controls. Concentration-response curves indicated that preparations from displaced abomasa showed reduced sensitivity to acetylcholine. This study demonstrated motility disorders in displaced abomasa in vitro. The results suggested that abomasal displacement is associated with malfunctions at the level of the intrinsic nervous system combined with impaired cholinergic muscle responses. There appeared to be a predominance of nitrergic inhibitory mechanisms over excitatory mechanisms. These results might be of significance for diseases associated with gastric hypomotility and emptying disorders.

Reference ranges for gastrointestinal transit of barium-impregnated polyethylene spheres in healthy cats

Commercial barium-impregnated polyethylene spheres (BIPS) were administered to 12 healthy adult cats according to the manufacturer's instructions (30 small BIPS and 10 large BIPS to each cat) together with 60 g of a canned food. Radiographs were taken at hourly intervals until seven hours after feeding, and then at eight, 10, 12, 14, 17, 23 and 30 hours or until all the BIPS had left the stomach and at least 50 per cent had entered the colon. Six cats were sedated immediately after being fed the BIPS and six cats remained unsedated. For small BIPS (1.5 mm diameter), the gastric transit time (first exit of BIPS from the stomach) in the sedated cats had a median of 6 hours (range 3 to 8) and in the unsedated cats a median of 2.5 hours (range 2 to 6). Values for other transit times were not significantly different between the two groups, and the pooled data revealed a median 50 per cent gastric emptying time of 6.4 hours (range 2.5 to 10.9), a complete gastric emptying time of 12 hours (range 6 to 27), an orocaecal transit time (first appearance of BIPS in the colon) of 6.5 hours (range 4.0 to 12.0) and a 50 per cent orocaecal transit time of 8.8 hours (range 4.6 to 12.8). The gastrointestinal transit of large BIPS (5 mm diameter) was significantly correlated with the passage of small BIPS but, except for the complete gastric emptying time, was significantly slower.

Review article: the use of botulinum toxin in the alimentary tract

New and future indications for the treatment of disorders of the alimentary tract using local injections of botulinum toxin are reviewed. Clinical experience shows that overactive smooth muscle sphincters may be weakened to treat disorders such as achalasia or chronic anal fissure. By contrast, injections placed into the sphincter of Oddi have proven less effective for postcholecystectomy pain syndrome. Experimental evidence suggests that food intake may be reduced by weakening the distal stomach with botulinum toxin. This approach may possibly lead to the treatment of obesity. There are some new possible indications for the use of botulinum toxin on the alimentary tract, and infantile hypertrophic pyloric stenosis seems to be the most promising new development.

Role of nuclear medicine in evaluating patients with suspected gastrointestinal motility disorders

Functional symptoms caused by gastrointestinal motility disorders are relatively common in the general population. Knowledge of the relationship between symptoms and the underlying gastrointestinal dysmotility provides physicians with a framework for successful evaluation and treatment of patients with possible motor disorders of the gastrointestinal tract. Scintigraphy provides for noninvasive and quantitative assessment of physiological transit throughout the gastrointestinal tract, and it is extremely useful for diagnosing gastrointestinal motor dysfunction. The wide range of scintigraphic studies now available supplement other diagnostic tests for evaluation of all segments of the gastrointestinal tract.

From motilin to motilides: a new direction in gastrointestinal endocrinology

Investigation into gastrointestinal irritation from the use of erythromycin lead to the discovery of the gastrointestinal motor effect of this antibiotic. Erythromycin and gastrointestinal peptide motilin share many similar gastrokinetic activities, and studies indicate that erythromycin mimics the effect of motilin through motilin receptor agonism. Since erythromycin is readily available for clinical use, it may offer an alternative therapeutic approach to gastroparesis and related conditions. Several analogs of erythromycin without antimicrobial activity are also shown to possess similar motor effects, thus termed "motilides". A growing number of motilides may expand our knowledge on gastrointestinal peptides.