Neuronal Control of Esophageal Peristalsis and Its Role in Esophageal Disease

Position-independent functional refinement within the vagus motor topographic map

Motor neurons in the central nervous system often lie in a continuous topographic map, where neurons that innervate different body parts are spatially intermingled. This is the case for the efferent neurons of the vagus nerve, which innervate diverse muscle and organ targets in the head and viscera for brain-body communication. It remains elusive how neighboring motor neurons with different fixed peripheral axon targets develop the separate somatodendritic (input) connectivity they need to generate spatially precise body control. Here we show that vagus motor neurons in the zebrafish indeed generate spatially appropriate peripheral responses to focal sensory stimulation even when they are transplanted into ectopic positions within the topographic map, indicating that circuit refinement occurs after the establishment of coarse topography. Refinement depends on motor neuron synaptic transmission, suggesting that an experience-dependent periphery-to-brain feedback mechanism establishes specific input connectivity amongst intermingled motor populations.

Polysaccharide-dextrin thickened fluids for individuals with dysphagia: recent advances in flow behaviors and swallowing assessment methods

The global aging population has brought about a pressing health concern: dysphagia. To effectively address this issue, we must develop specialized diets, such as thickened fluids made with polysaccharide-dextrin (e.g., water, milk, juices, and soups), which are crucial for managing swallowing-related problems like aspiration and choking for people with dysphagia. Understanding the flow behaviors of these thickened fluids is paramount, and it enables us to establish methods for evaluating their suitability for individuals with dysphagia. This review focuses on the shear and extensional flow properties (e.g., viscosity, yield stress, and viscoelasticity) and tribology (e.g., coefficient of friction) of polysaccharide-dextrin-based thickened fluids and highlights how dextrin inclusion influences fluid flow behaviors considering molecular interactions and chain dynamics. The flow behaviors can be integrated into the development of diverse evaluation methods that assess aspects such as flow velocity, risk of aspiration, and remaining fluid volume. In this context, the key in-vivo (e.g., clinical examination and animal model), in-vitro (e.g., the Cambridge Throat), and in-silico (e.g., Hamiltonian moving particles semi-implicit) evaluation methods are summarized. In addition, we explore the potential for establishing realistic assessment methods to evaluate the swallowing performance of thickened fluids, offering promising prospects for the future.

Key Stress Response Mechanisms of Probiotics During Their Journey Through the Digestive System: A Review

The survival of probiotic microorganisms during their exposure to harsh environments plays a critical role in the fulfillment of their functional properties. In particular, transit through the human gastrointestinal tract (GIT) is considered one of the most challenging habitats that probiotics must endure, because of the particularly stressful conditions (e.g., oxygen level, pH variations, nutrient limitations, high osmolarity, oxidation, peristalsis) prevailing in the different sections of the GIT, which in turn can affect the growth, viability, physiological status, and functionality of microbial cells. Consequently, probiotics have developed a series of strategies, called "mechanisms of stress response," to protect themselves from these adverse conditions. Such mechanisms may include but are not limited to the induction of new metabolic pathways, formation/production of particular metabolites, and changes of transcription rates. It should be highlighted that some of such mechanisms can be conserved across several different strains or can be unique for specific genera. Hence, this review attempts to review the state-of-the-art knowledge of mechanisms of stress response displayed by potential probiotic strains during their transit through the GIT. In addition, evidence whether stress responses can compromise the biosafety of such strains is also discussed.

The impact of primary peristalsis, contractile reserve, and secondary peristalsis on esophageal clearance measured by timed barium esophagogram

BACKGROUND

Primary and secondary peristalsis facilitate esophageal bolus transport; however, their relative impact for bolus clearance remains unclear. We aimed to compare primary peristalsis and contractile reserve on high-resolution manometry (HRM) and secondary peristalsis on functional lumen imaging probe (FLIP) Panometry with emptying on timed barium esophagogram (TBE) and incorporate findings into a comprehensive model of esophageal function.

METHODS

Adult patients who completed HRM with multiple rapid swallows (MRS), FLIP, and TBE for esophageal motility evaluation and without abnormal esophagogastric junction outflow/opening or spasm were included. An abnormal TBE was defined as a 1-min column height >5 cm. Primary peristalsis and contractile reserve after MRS were combined into an HRM-MRS model. Secondary peristalsis was combined with primary peristalsis assessment to describe a complementary neuromyogenic model.

KEY RESULTS

Of 89 included patients, differences in rates of abnormal TBEs were observed with primary peristalsis classification (normal: 14.3%; ineffective esophageal motility: 20.0%; absent peristalsis: 54.5%; p = 0.009), contractile reserve (present: 12.5%; absent: 29.3%; p = 0.05), and secondary peristalsis (normal: 9.7%; borderline: 17.6%; impaired/disordered: 28.6%; absent contractile response: 50%; p = 0.039). Logistic regression analysis (akaike information criteria, area under the receiver operating curve) demonstrated that the neuromyogenic model (80.8, 0.83) had a stronger relationship predicting abnormal TBE compared to primary peristalsis (81.5, 0.82), contractile reserve (86.8, 0.75), or secondary peristalsis (89.0, 0.78).

CONCLUSIONS AND INFERENCES

Primary peristalsis, contractile reserve, and secondary peristalsis were associated with abnormal esophageal retention as measured by TBE. Added benefit was observed when applying comprehensive models to incorporate primary and secondary peristalsis supporting their complementary application.

Numerical simulation of peristalsis to study co-localization and intestinal distribution of a macromolecular drug and permeation enhancer

In this work, simulations of intestinal peristalsis are performed to investigate the intraluminal transport of macromolecules (MMs) and permeation enhancers (PEs). Properties of insulin and sodium caprate (C₁₀) are used to represent the general class of MM and PE molecules. Nuclear magnetic resonance spectroscopy was used to obtain the diffusivity of C₁₀, and coarse-grain molecular dynamics simulations were carried out to estimate the concentration-dependent diffusivity of C₁₀. A segment of the small intestine with the length of 29.75 cm was modeled. Peristaltic speed, pocket size, release location, and occlusion ratio of the peristaltic wave were varied to study the effect on drug transport. It was observed that the maximum concentration at the epithelial surface for the PE and the MM increased by 397 % and 380 %, respectively, when the peristaltic wave speed was decreased from 1.5 to 0.5 cm s^-1. At this wave speed, physiologically relevant concentrations of PE were found at the epithelial surface. However, when the occlusion ratio is increased from 0.3 to 0.7, the concentration approaches zero. These results suggest that a slower-moving and more contracted peristaltic wave leads to higher efficiency in transporting mass to the epithelial wall during the peristalsis phases of the migrating motor complex.

Comparing Patients Diagnosed With Ineffective Esophageal Motility by the Chicago Classification Version 3.0 and Version 4.0 Criteria

Background

The Chicago Classification version 4.0 (CCv4.0) of ineffective esophageal motility (IEM) is more stringent than the Chicago Classification version 3.0 (CCv3.0) definition. We aimed to compare the clinical and manometric features of patients meeting CCv4.0 IEM criteria (group 1) versus patients meeting CCv3.0 IEM but not CCv4.0 criteria (group 2).

Methods

We collected retrospective clinical, manometric, endoscopic, and radiographic data on 174 adults diagnosed with IEM from 2011 to 2019. Complete bolus clearance was defined as evidence of exit of the bolus by impedance measurement at all distal recording sites. Barium studies included barium swallow, modified barium swallow, and barium upper gastrointestinal series studies, and collected data from these reports include abnormal motility and delay in the passage of liquid barium or barium tablet. These data along with other clinical and manometric data were analyzed using comparison and correlation tests. All records were reviewed for repeated studies and the stability of the manometric diagnoses.

Results

Most demographic and clinical variables were not different between the groups. A lower mean lower esophageal sphincter pressure was correlated with greater percent of ineffective swallows in group 1 (n = 128) (r = -0.2495, P = 0.0050) and not in group 2. In group 1, increased percent of failed contractions on manometry was associated with increased incomplete bolus clearance (r = 0.3689, P = 0.0001). No such association was observed in group 2. A lower median integrated relaxation pressure was correlated with greater percent of ineffective contractions in group 1 (r = -0.1825, P = 0.0407) and not group 2. Symptom of dysphagia was more prevalent (51.6% versus 69.6%, P = 0.0347) in group 2. Dysphagia was not associated with intrabolus pressure, bolus clearance, barium delay, or weak or failed contractions in either group. In the small number of subjects with repeated studies, a CCv4.0 diagnosis appeared more stable over time.

Conclusions

CCv4.0 IEM was associated with worse esophageal function indicated by reduced bolus clearance. Most other features studied did not differ. Symptom presentation cannot predict if patients are likely to have IEM by CCv4.0. Dysphagia was not associated with worse motility, suggesting it may not be primarily dependent on bolus transit.

Preexisting neural factors that contribute to dysmotility in esophageal atresia: a systematic review

Esophageal dysmotility in esophageal atresia (EA) relates to abnormal development of esophageal innervation and musculature and to the esophageal repair. Few studies have investigated the preexisting dysmotility in EA, present prior to surgery. This systematic review aims to summarize the literature on neuronal studies in EA, to understand the causative factors for esophageal dysmotility. We performed a systematic review (PubMed, EMBASE, EBM, CINAHL databases; January 1947-February 2021) in accordance with PRISMA (PROSPERO number CRD42020171014). Fourteen studies were identified (eleven human, 187 EA patients; three animal, 64 EA rat specimens). Neural factors affecting esophageal dysmotility in human and animal studies included proteins, enzymes, growth factors, and genes, which play a role in the nervous system or neuroendocrine system, some of which have functions as neuromodulators or neurotransmitters. This systematic review has identified neural factors that affect esophageal dysmotility and contributes toward our understanding of the underlying dysmotility in patients with EA. The studies identified are important and essential for successful translation of basic science knowledge to impact clinical practice and understanding. Level of evidence: III.

Congenital idiopathic megaesophagus in the German shepherd dog is a sex-differentiated trait and is associated with an intronic variable number tandem repeat in Melanin-Concentrating Hormone Receptor 2

Congenital idiopathic megaesophagus (CIM) is a gastrointestinal (GI) motility disorder of dogs in which reduced peristaltic activity and dilation of the esophagus prevent the normal transport of food into the stomach. Affected puppies regurgitate meals and water, fail to thrive, and experience complications such as aspiration pneumonia that may necessitate euthanasia. The German shepherd dog (GSD) has the highest disease incidence, indicative of a genetic predisposition. Here, we discover that male GSDs are twice as likely to be affected as females and show that the sex bias is independent of body size. We propose that female endogenous factors (e.g., estrogen) are protective via their role in promoting relaxation of the sphincter between the esophagus and stomach, facilitating food passage. A genome-wide association study for CIM revealed an association on canine chromosome 12 (P-val = 3.12x10^-13), with the lead SNPs located upstream or within Melanin-Concentrating Hormone Receptor 2 (MCHR2), a compelling positional candidate gene having a role in appetite, weight, and GI motility. Within the first intron of MCHR2, we identified a 33 bp variable number tandem repeat (VNTR) containing a consensus binding sequence for the T-box family of transcription factors. Across dogs and wolves, the major allele includes two copies of the repeat, whereas the predominant alleles in GSDs have one or three copies. The single-copy allele is strongly associated with CIM (P-val = 1.32x10^-17), with homozygosity for this allele posing the most significant risk. Our findings suggest that the number of T-box protein binding motifs may correlate with MCHR2 expression and that an imbalance of melanin-concentrating hormone plays a role in CIM. We describe herein the first genetic factors identified in CIM: sex and a major locus on chromosome 12, which together predict disease state in the GSD with greater than 75% accuracy.

German shepherd dogs (GSDs) are predisposed to an inherited motility disorder of the esophagus, termed congenital idiopathic megaesophagus (CIM), in which swallowing is ineffective and the esophagus is enlarged. Affected puppies are unable to properly pass food into their stomachs and consequently regurgitate their meals and show a failure to thrive, often leading to euthanasia. Here, we discovered that male GSDs are affected at a ratio of almost 2-to-1 over females, suggesting a protective biological advantage in females. In humans, estrogen is thought to play a role in the male predominance of esophageal disorders like reflux esophagitis and esophageal cancer. In a genome-wide scan, we identified an association with CIM on chromosome 12 and, within this region, a repetitive sequence in MCHR2. This gene encodes a receptor for melanin-concentrating hormone, a signaling molecule that is linked to appetite, weight, and gut motility. Together, sex and the MCHR2 repeat sequence accurately predict affection status in over 75% of dogs, and a genetic test is now available to facilitate breeding decisions aimed at reducing disease incidence.

Schwann Cells in Digestive System Disorders

Proper functioning of the digestive system is ensured by coordinated action of the central and peripheral nervous systems (PNS). Peripheral innervation of the digestive system can be viewed as intrinsic and extrinsic. The intrinsic portion is mainly composed of the neurons and glia of the enteric nervous system (ENS), while the extrinsic part is formed by sympathetic, parasympathetic, and sensory branches of the PNS. Glial cells are a crucial component of digestive tract innervation, and a great deal of research evidence highlights the important status of ENS glia in health and disease. In this review, we shift the focus a bit and discuss the functions of Schwann cells (SCs), the glial cells of the extrinsic innervation of the digestive system. For more context, we also provide information on the basic findings regarding the function of innervation in disorders of the digestive organs. We find diverse SC roles described particularly in the mouth, the pancreas, and the intestine. We note that most of the scientific evidence concerns the involvement of SCs in cancer progression and pain, but some research identifies stem cell functions and potential for regenerative medicine.

Dysphagia and Swallowing Disorders

Dysphagia, defined as impairment of the swallowing process, is a common symptom and can be a significant source of morbidity and mortality in the general population. This article summarizes the causes of the condition, its prevalence, and the consequences and costs of untreated dysphagia. The aim of this article is to provide a framework for the general internist in assessing, diagnosing, and managing dysphagia in an adult patient. Basic diagnostic screening procedures and techniques for management are emphasized. A basic treatment pathway based on cause is provided for reference.

Patterns of esophageal dysmotility elicited by multiple rapid swallows

BACKGROUND

High-resolution manometry (HRM) is a gastrointestinal motility diagnostic system that measures intraluminal pressures using closely aligned sensors. Multiple rapid swallows (MRS) are used in conjunction with HRM to assess esophageal physiology prior to anti-reflux and hiatal hernia procedures.

METHODS

A retrospective, qualitative study was conducted on 90 patients who underwent HRM with MRS in a single community clinic. 80 patients met the inclusion criteria. MRS testing consisted of rapid 2 mL swallows in 2-3 s intervals with patients in a seated, upright position. Clinical information was reviewed including indications for HRM, prior diagnostic workup, manometry, distal contractile integral (DCI), and integrated residual pressure (IRP). HRM studies were visualized using Manoview Analysis Software v3.0 (Medtronic).

RESULTS

Certain esophageal dysmotility and pressurization manometry patterns were previously undetected on HRM alone. In our study, the addition of MRS was clinically helpful in (1) assessing contraction reserve, (2) highlighting features of jackhammer, (3) stimulating esophageal spasm, and (4) visualizing distal esophageal pressurization pattern with mechanical obstruction. Additionally, abnormal pathophysiology such as (5) paradoxical LES contraction (achalasia) and (6) loss of deglutition inhibition were identified. MRS had a diagnostic utility of 21.25% (n = 17) among the 80 patients. An intolerance rate of 7.7% (n = 7) was observed in patients unable to complete the protocol.

CONCLUSIONS

Augmentation of HRM with MRS produces unique manometric features that have clinical utility in uncovering esophageal disorders. MRS provocation testing is a practical, inexpensive, well-tolerated addition to HRM that may yield useful clinical information to guide complicated diagnoses and medical management.

Belching in Gastroesophageal Reflux Disease: Literature Review

Belching is a common phenomenon. However, it becomes bothersome if excessive. Impedance–pH monitoring can classify the belching into two types: gastric belching and supragastric belching (SGB). The former is a physiological mechanism to vent swallowed air from the stomach, whereas the latter is a behavioral disorder. Gastroesophageal reflux disease (GERD) is the most relevant condition in both types of belching. Recent findings have raised awareness that excessive SGB possibly sheds light on the pathogenesis of a part of proton pump inhibitor (PPI) refractoriness in GERD. SGB could cause typical reflux symptoms such as heartburn, regurgitation or chest pain in two ways: SGB-induced gastroesophageal reflux or SGB-induced esophageal distension. In PPI-refractory GERD, it is important to detect hidden SGB as a cause of reflux symptoms since SGB requires psychological treatment instead of high dose PPIs or pain modulators. In the case of PPI-refractory GERD with excessive SGB, recent studies imply that the combination of a psychological approach and conventional treatment can improve treatment outcome.

Esophageal physiology-an overview of esophageal disorders from a pathophysiological point of view

The esophagus serves the principal purpose of transporting food from the pharynx into the stomach. A complex interplay between nerves and muscle fibers ensures that swallowing takes place as a finely coordinated event. Esophageal function can be tested by a variety of methods, endoscopy, manometry, and reflux monitoring being some of the most important. Regarding pathophysiology, motor disorders, such as achalasia, often cause dysphagia and/or chest pain. Functional esophageal disorders are a heterogeneous group with hypersensitivity as a dominant pathophysiological factor. Gastroesophageal reflux disease often causes symptoms, such as heartburn and regurgitation, and a spectrum of disease, ranging from minimal mucosal damage visible only in the microscope to esophageal ulcers and strictures in the most severe cases. Eosinophilic esophagitis is an immune-mediated condition that can result in significant dysphagia and associated luminal narrowing. In the following, we will provide an overview of the most common esophageal disorders from a combined pathophysiological and clinical view.

Recommendations of the Russian Gastroenterological Association on Clinical Use of High-Resolution Manometry in Diagnosis of Esophageal Disorders

Aim. Current recommendations of the Russian Gastroenterological Association on clinical use of high-resolution manometry in diagnosis of esophageal disorders are intended to assist in clinical decision making, terminology standardisation and interpretation of clinical data.

Key points. In 2018, a joint meeting of the Russian Gastroenterological Association and Russian Neurogastroenterology and Motility Group approved unified terminology and classification of esophageal motor function disorders for high-resolution manometry diagnosis.

Gastrointestinal patient complaints typically concern esophageal disorders such as dysphagia, regurgitation, heart-burn, chest pain or belching. To exclude erosive and ulcerative lesions, eosinophilic esophagitis and organic changes, esophagogastroduodenoscopy and biopsy are recommended in pre-treatment. Upon excluding mucosal lesions and esophageal lumen obstruction as causal for symptoms, use of high-resolution manometry is recommended. This method of esophageal examination has become the “gold standard” in diagnosis of motor disorders.

High-resolution manometry enables detailed investigation of integral quantitative and qualitative characteristics of esophagus motor function and specific related disorders, analysis of esophageal contractile propagation and strictly coordinated synchronous peristalsis of upper esophageal sphincter, esophagus and lower esophageal sphincter, which malfunction may provoke development of achalasia, esophagospasm, hiatal hernia, ineffective eso pha geal motility and other motor disorders.

Conclusion. High-resolution manometry is a relatively new method for study of esophagus motor function gaining increasingly wide application in clinical practice. It enables a medical professional to obtain evidence that may critically affect the choice of optimal patient care strategy and effective treatment. Current recommendations are based on an extensive review of up-to-date information and will be updated with new corpus of clinical data and assessment emerging in evidential medicine to provide gastroenterologists country-wide with latest scientific and practical guidelines.