Physiological and Pathophysiological Roles of VIP, Somatostatin, Opioids, Galanin, GRP, and Secretin
Edwin E. Daniel in Neuropeptide Function in the Gastrointestinal Tract, 2019
The interdigestive migrating motor complex (MMC) is one phase of a recurring motility pattern of stomach and small intestine in the fasting state characterized by a quiescent period (phase I), intermittent activity (phase II), and a period of rhythmic contractions occurring at maximal frequency (MMC or phase III). The activity in phase III normally begins in the LES and stomach and frequently migrates to the terminal ileum. Peeters et al.71 proposed a physiological role for somatostatin in the regulation of this activity in man. Somatostatin inhibited all gastric activity and accelerated the progression of phase III in the small intestine. Hormonal, neural, and myogenic factors are involved in the regulation of the MMC. Somatostatin probably is involved, but related to many other factors. Motilin may be involved in initiation of phase III in the stomach. Somatostatin inhibits release of motilin and the effect of motilin on the proximal gut.72 In some studies, somatostatin levels are increased during phase III.72,73 Bueno et al.73 studied the role of somatostatin in the pig. Although somatostatin inhibited gastrointestinal activity in the pig, no role was obvious in the regulation of the MMC. However, the dietary habits of the pig (snacking without real fasting periods) suggest that regulation of the MMC must differ from that in other species.
Pathophysiology and Management of Diabetic Gastropathy
Emmanuel Opara in NUTRITION and DIABETES, 2005
Erythromycin is a macrolide antibiotic that has prokinetic properties through its presumed activation of motilin receptors.119 This agent may increase the amplitude and frequency of antral contractions, as well as initiation of gastric phase three contractions of the migrating motor complex.120–121 There is a motilin-receptor gradient in mammalian gastrointestinal tract, with the highest concentrations identified in the upper-gastrointestinal tract.122 Administration of erythromycin has been reported to improve solid and liquid gastric emptying in diabetic, postvagotomy, and idiopathic gastroparesis.123–127 Intravenous doses in acute treatment range between 1 to 3 mg/kg every eight hours. The commonly used oral doses are between 50 to 250 mg/kg every six to eight hours. Although the optimal dosing and route of administration has not yet been resolved, oral regimen does not appear to be as effective as intravenous administration.128 Unfortunately, the long-term efficacy of erythromycin has been unsatisfactory and may include the risks of long-term antibiotic use.129 Adverse events induced by erythromycin include abdominal pain, cramping, nausea, and vomiting.
The Physiology of Digestion, Absorption, and Metabolism in the Human Intestine
Victor R. Preedy, Ronald R. Watson in Alcohol and the Gastrointestinal Tract, 2017
In the fasting state200 small intestinal motility is characterized by a period of inactivity (Phase I) followed by Phase II, a period of irregular spike activity lasting (like Phase I) for 30 to 40 min. Pressure activity increases steadily during the latter half of Phase II ushering in Phase III, during which there are intense repetitive high amplitude contractions. Phase III lasts for about 4 to 6 min of irregular activity (Phase IV), which then gives way to a new Phase I. The whole cycle of activity migrates down the upper small intestine at 4 to 6 cm/min, slowing distally to 1 to 2 cm/min in the terminal ileum. This migrating motor complex, referred to as the MMC, is thought to have the function of sweeping debris down the small intestine and does not occur until 4 to 6 h after a meal. The fasting pattern of motility is disrupted by feeding, and irregular activity is seen throughout the small intestine. It resembles that seen during Phase II of the MMC and hence is called "type II activity." Contraction frequency and speed are reduced by nutrients, thereby prolonging transit time.201 The intestine appears able to discriminate between different nutrients since there are qualitative differences in motor response, fat generating particularly intense nonpropagating clustered contractions whose function is presumably to aid emulsification and hence absorption. In essence, therefore, the fasting function of the motility response is to propagate debris distally and the fed response is basically nonpropagative in type to aid digestion and absorption of nutrients.202
Alopecia areata and the gut—the link opens up for novel therapeutic interventions
Published in Expert Opinion on Therapeutic Targets, 2018
Normally, relatively few bacteria live in the small intestine (less than 10,000 bacteria per milliliter of fluid) as compared with the colon (at least 1,000,000,000 bacteria per milliliter of fluid) and the types of bacteria in the small intestine are not the same as those in the colon [18]. They play an important role in digesting food and absorbing nutrients but are also important regulators of the immune system with its impressive network of lymphoid cells in the intestinal submucosa. Moreover, the bacteria help maintain the normal muscular activity of the small bowel (Migrating Motor Complex, MMC). The MMC is responsible for moving the intestinal content through the gut, but most importantly, to clean the small intestine in between meals so that bacteria cannot overgrow. The MMC seems to be the most frequent dysfunction in people with SIBO [74] but also proper gastric acid secretion, biliary and pancreatic secretions, immunoglobulins in the intestinal fluid and the ileocecal valve (which allows the flow of bowel contents into the large intestine but prevents them from refluxing back into the small intestine) are important for an adequate small intestinal function [76].
Intragastric quinine administration decreases hedonic eating in healthy women through peptide-mediated gut-brain signaling mechanisms
Published in Nutritional Neuroscience, 2019
Julie Iven, Jessica R. Biesiekierski, Dongxing Zhao, Eveline Deloose, Owen G. O’Daly, Inge Depoortere, Jan Tack, Lukas Van Oudenhove
Distinguishing bitter taste allows detection of toxic compounds in food.1 However, some people have a preference for bitter taste, depending on their sensitivity to bitter compounds, which is sex-dependent, with women on average being more sensitive.1,2 Bitter tastants (i.e. chemicals stimulating the sense of taste) are sensed via taste receptors of the taste 2 receptor family (TAS2R) class of G-protein coupled receptors, located on taste receptor cells in lingual taste buds. However, TAS2Rs are also present on enteroendocrine cells (EEC) throughout the gastrointestinal (GI) tract.3 Activation of taste receptors on EECs occurs via a chemosensory signaling pathway and results in altered secretion of GI peptide hormones involved in the regulation of food intake.4 More specifically, TAS2Rs are present on ghrelin-producing X/A-like cells in the gastric fundus, among others. Ghrelin, a 28-amino acid peptide, is the key orexigenic GI hormone as its plasma levels peak pre-prandially and decrease rapidly with food ingestion.5 Motilin, a polypeptide hormone secreted by EECs in the duodenum, jejunum, and neurons of the myenteric plexus, is the regulator of the migrating motor complex (MMC), a cyclic secretomotor pattern during the fasted state that originates in the stomach and small bowel. Plasma motilin levels fluctuate with the phases of the MMC, and motilin-induced gastric phase III contractions coincide with increases in fasting hunger ratings, pointing towards an orexigenic effect of motilin.6,7
Therapeutic effects of Bombax ceiba flower aqueous extracts against loperamide-induced constipation in mice
Published in Pharmaceutical Biology, 2023
Liuping Wang, Shiyuan Xie, Xuan Jiang, Caini Xu, Youqiong Wang, Jianfang Feng, Bin Yang
The gastrointestinal motility-related biomarkers secreted by the intestinal nerve network act as neuromodulators and neurotransmitters to promote intestinal peristalsis and transportation, including excitatory factors (MTL, SP, Gas, etc.) (Yin et al. 2018) and inhibitory factor (SS, NO, etc.) (Gan et al. 2020). Abnormal secretion of enteric motility-related biomarkers may be the main pathogenesis of constipation (Liu et al. 2020). MTL is the intestinal hormone which can increase the migrating motor complex of gastrointestinal motility (Yin et al. 2018), but it has lower serum MTL levels in constipation children (Sun et al. 2020). As an excitatory neurotransmitter of intestinal nerve network, SP strongly promotes smooth muscle contraction, promotes gastrointestinal peristalsis and stimulates intestinal water and electrolyte secretion (Li et al. 2020). Gas, mainly secreted by G cells in the pyloric antrum of the stomach (Iijima et al. 2014), promotes gastrointestinal motility and stimulates the secretion of gastric acid by the parietal cells of the stomach (Gan et al. 2020). However, the secretion of Gas is inhibited by SS (Jiang et al. 2020). SS could suppress the movement of gastrointestinal smooth muscle and inhibit the secretion of gastrointestinal hormones (Han 2013). According to current ELISA results, with the intervention of phenolphthalein, MTL was increased but SS was decreased compared with the model group. In addition, compared with the model group, BCE significantly increased levels of serum MTL, SP, Gas, while inhibited serum SS. Nevertheless, the concrete relationship and mechanism between them still need further research.
Related Knowledge Centers
- Bone
- Dietary Fiber
- Gastrointestinal Tract
- Peristalsis
- Small Intestine
- Stomach
- Large Intestine
- Fasting
- Ileocecal Valve
- Stomach Rumble