Intragastric pressure during food intake: a physiological and minimally invasive method to assess gastric accommodation

The combination of L-menthol and caraway oil does not affect gastric function but increases hunger in healthy subjects

BACKGROUND

The heterogeneous character of functional gastrointestinal disorders, recently renamed into disorders of gut-brain interaction, makes finding effective treatment options challenging. Compared to synthetic drugs, phytotherapy can have broader pharmacological effects and is often better tolerated. This study aimed to investigate the effect of peppermint oil and caraway oil (POCO) on gastric function and symptom levels in 32 healthy subjects in a single-blinded, placebo-controlled, randomized, parallel design.

METHODS

Gastric emptying rate was assessed using a 13C-breath test. Intragastric pressure was measured using high-resolution manometry in fasted state and during intragastric infusion of a nutrient drink (350 mL or until full satiation). GI symptoms were rated on a 100 mm VAS. Data were analyzed using linear mixed models.

KEY RESULTS

POCO had no effect on intragastric pressure in fasted or fed state (p > 0.08 for all). No significant differences in gastric emptying rate were observed (p = 0.54). In the fasted state, a stronger increase in hunger and decrease in satiety were observed following POCO (p = 0.016 and p = 0.008, respectively). No differences in hunger and satiety were observed in the fed state (p > 0.31 for all). POCO induced less epigastric burning, bloating, and fullness (p < 0.05 for all).

CONCLUSIONS

Acute POCO administration did not affect gastric function in healthy subjects, but increased fasted hunger ratings. The effects of POCO on gastric function and hunger sensations in patients with disorders of gut-brain interaction, and the contribution to symptom improvement, needs to be elucidated in future studies.

The gut-brain axis in appetite, satiety, food intake, and eating behavior: Insights from animal models and human studies

The gut-brain axis plays a pivotal role in the finely tuned orchestration of food intake, where both homeostatic and hedonic processes collaboratively control our dietary decisions. This interplay involves the transmission of mechanical and chemical signals from the gastrointestinal tract to the appetite centers in the brain, conveying information on meal arrival, quantity, and chemical composition. These signals are processed in the brain eventually leading to the sensation of satiety and the termination of a meal. However, the regulation of food intake and appetite extends beyond the realms of pure physiological need. Hedonic mechanisms, including sensory perception (i.e., through sight, smell, and taste), habitual behaviors, and psychological factors, exert profound influences on food intake. Drawing from studies in animal models and human research, this comprehensive review summarizes the physiological mechanisms that underlie the gut-brain axis and its interplay with the reward network in the regulation of appetite and satiety. The recent advancements in neuroimaging techniques, with a focus on human studies that enable investigation of the neural mechanisms underpinning appetite regulation are discussed. Furthermore, this review explores therapeutic/pharmacological strategies that hold the potential for controlling food intake.

Computer modeling of digestive processes in the alimentary tract and their physiological regulation mechanisms: closing the gap between digestion models and in vivo behavior

Introduction

A model has been developed for in silico simulation of digestion and its physiological feedback mechanisms.

Methods

The model is based on known physiology described in the literature and is able to describe the complexity of many simultaneous processes related to food digestion.

Results

Despite the early stage of development of the model, it already encompasses a large number of processes that occur simultaneously, enabling the prediction of a large number of post-prandial physiological markers, which can be highly functional in combination with in vitro, organ-on-a-chip and digital twin models purposed to measure the physiological properties of organs and to predict the effect of adjusted food composition in normal and diseased states.

Discussion

Input from and collaboration between science fileds is needed to further develop and refine the model and to connect with in vitro, in vivo, and ex vivo (organ-on-a-chip) models.

Abnormal gastrointestinal motility is a major factor in explaining symptoms and a potential therapeutic target in patients with disorders of gut-brain interaction

The objective of this article is to review the evidence of abnormal gastrointestinal (GI) tract motor functions in the context of disorders of gut-brain interaction (DGBI). These include abnormalities of oesophageal motility, gastric emptying, gastric accommodation, colonic transit, colonic motility, colonic volume and rectal evacuation. For each section regarding GI motor dysfunction, the article describes the preferred methods and the documented motor dysfunctions in DGBI based on those methods. The predominantly non-invasive measurements of gut motility as well as therapeutic interventions directed to abnormalities of motility suggest that such measurements are to be considered in patients with DGBI not responding to first-line approaches to behavioural or empirical dietary or pharmacological treatment.

Comparison of purse-string suture versus over-the-scope clip for gastric endoscopic full-thickness closure: traction and leak pressure testing in ex vivo porcine model

BACKGROUND

The recently developed endoscopic full-thickness resection technique requires reliable closure. The main closure methods are the purse-string suture (PSS) technique and over-the-scope clip (OTSC) technique; however, basic data on the closure strength of each technique are lacking. This study was performed to compare the closure strengths of these two methods in an ex vivo porcine model.

METHODS

In the traction test, a virtual 5-cm full-thickness closure line was closed by the following six methods three times each: conventional hemoclips, mucosal PSS, seromuscular PSS, mucosal OTSC, seromuscular OTSC, and surgical suture. The primary endpoint was the tension at the starting point of dehiscence, measured in Newtons (N) by an automatic traction machine. In the leak test, a 15-mm gastric full-thickness defect was closed by PSS or OTSC six times each, and the closed stomach was then pressurized in a water container. The primary endpoint was the leak pressure when air bubbles appeared. The secondary endpoints were the procedure time and presence of complete inverted closure.

RESULTS

The mean tension was 2.16, 3.68, 5.15, 18.30, 19.30, and 62.40 N for conventional hemoclips, mucosal PSS, seromuscular PSS, mucosal OTSC, seromuscular OTSC, and surgical suture, respectively. Complete inverted closure was observed for seromuscular PSS, seromuscular OTSC, and surgical suture. The mean leak pressure was 13.7 and 24.8 mmHg in the PSS and OTSC group, respectively (P < 0.01). The mean procedure time was 541 and 169 s in the PSS and OTSC group, respectively (P < 0.01). Complete inverted closure was observed in OTSC alone.

CONCLUSION

The OTSC, which allows complete inverted closure, showed greater closure strength than PSS. Considering the size limitation suitable for single OTSC, a therapeutic strategy for closing the larger size is further warranted.

Gastric sensorimotor function and its clinical measurement

BACKGROUND

Gastroduodenal symptoms are highly prevalent, with underlying sensorimotor dysfunction contributing in many patients. Common symptoms include early satiation, postprandial fullness, epigastric bloating, pain or burning, nausea and vomiting, which collectively affect over 7% of adults. However, the clinical evaluation of these symptoms remains challenging, with current tests of gastric function remaining limited in their ability or availability to separate specific patient subgroups or guide-targeted care.

PURPOSE

In the current edition of Neurogastroenterology & Motility, Silver et al. present new data showing correlations between patterns of intragastric meal distribution and symptom profiles in a large series of patients undergoing gastric emptying scintigraphy. Studies of this type are important, as they motivate understanding beyond existing disease labels, and orient focus toward deeper mechanistic profiling. This brief review provides an overview of gastric sensorimotor function and profiles several current and emerging methods of clinical evaluation. Perspectives are provided on accommodation testing, gastric emptying, measuring gastric myoelectrical activity including new approaches, and antroduodenal manometry. Although gastric physiology is complex, recent progress has been encouraging, with the heterogenous pathophysiology of gastric symptoms continuing to be unraveled, and new techniques for evaluating gastric function and symptoms emerging.

CONCLUSIONS AND INFERENCES

Ongoing progress will now depend on continuing to accurately profile the underlying mechanisms of gastroduodenal disorders to identify specific disease phenotypes that inform care.

Gastric accommodation: Physiology, diagnostic modalities, clinical relevance, and therapies

BACKGROUND

Gastric accommodation is an essential gastric motor function which occurs following ingestion of a meal. Impaired gastric fundic accommodation (IFA) is associated with dyspeptic symptoms. Gastric accommodation is mediated by the vagal pathway with several important physiologic factors such as duodenal nutrient feedback playing a significant role. IFA has been described as a pathophysiologic factor in several gastrointestinal disorders including functional dyspepsia, diabetic gastropathy, post-Nissen fundoplication, postsurgical gastrectomy, and rumination syndrome. Modalities for gastric accommodation assessment include gastric barostat, intragastric meal distribution via scintigraphy, drinking tests (eg, water load), SPECT, MRI, 2D and 3D ultrasound, and intragastric high-resolution manometry. Several treatment options including sumatriptan, buspirone, tandospirone, ondansetron, and acotiamide may improve symptoms by increasing post-meal gastric volume.

PURPOSE

Our aim is to provide an overview of the physiology, diagnostic modalities, and therapies for IFA. A literature search was conducted on PubMed, Google Scholar, and other sources to identify relevant studies available until December 2020. Gastric accommodation is an important gastric motor function which if impaired, is associated with several upper gastrointestinal disorders. There are an increasing number of gastric accommodation testing modalities; however, each has facets which warrant consideration. Evidence regarding potentially effective therapies for IFA is growing.

Diagnostic Evaluation of Gastric Motor and Sensory Disorders

Disorders of gastric motor and sensory function affect 10%-20% of the world's population and adversely impact nutrition, quality of life, work productivity, and health care costs. Classifying these disorders can be challenging given the heterogeneity of symptom presentation, the presence of symptoms unexplained by endoscopic, radiographic and/or laboratory evaluation, and overlap with other luminal gastrointestinal disorders. Accurately diagnosing these highly prevalent disorders relies upon an understanding of epidemiology and risk factors, the ability to take a careful clinical history focused on symptoms, and the presence of predisposing medical, surgical, and psychological conditions. A variety of diagnostic studies are now available to assess gastric motor function and identify maladaptive relaxation, accommodation, and abnormal sensation. FDA-approved treatment options are limited and thus many patients undergo a series of empirical treatment trials that target individual symptoms, often without much benefit. This article provides updated recommendations for identifying and classifying the most common gastric motor and sensory disorders using currently accepted diagnostic tests, and provides a brief supplemental overview on treatment options. "Things sweet to taste prove in digestion sour." -Shakespeare, Richard II, 1595.

Nitric Oxide: From Gastric Motility to Gastric Dysmotility

It is known that nitric oxide (NO) plays a key physiological role in the control of gastrointestinal (GI) motor phenomena. In this respect, NO is considered as the main non-adrenergic, non-cholinergic (NANC) inhibitory neurotransmitter responsible for smooth muscle relaxation. Moreover, many substances (including hormones) have been reported to modulate NO production leading to changes in motor responses, further underlying the importance of this molecule in the control of GI motility. An impaired NO production/release has indeed been reported to be implicated in some GI dysmotility. In this article we wanted to focus on the influence of NO on gastric motility by summarizing knowledge regarding its role in both physiological and pathological conditions. The main role of NO on regulating gastric smooth muscle motor responses, with particular reference to NO synthases expression and signaling pathways, is discussed. A deeper knowledge of nitrergic mechanisms is important for a better understanding of their involvement in gastric pathophysiological conditions of hypo- or hyper-motility states and for future therapeutic approaches. A possible role of substances which, by interfering with NO production, could prove useful in managing such motor disorders has been advanced.

Supraphysiological effects of pancreatic polypeptide on gastric motor function and nutrient tolerance in humans

Pancreatic polypeptide (PP) is known to affect food intake. In this exploratory study, we set out to investigate its supraphysiological effect on food tolerance, gastric accommodation, and emptying. In 12 healthy volunteers, 0, 3, or 10 pmol*kg-1 *min-1 PP was administered intravenously (PP0, PP3 or PP10). Thirty minutes thereafter, nutrient drink infusion (60 ml*min-1 ) through a nasogastric feeding tube was started until maximum satiation. Gastric accommodation was assessed by measuring the intragastric pressure (IGP; nasogastric manometry). In a separate test, the effect of PP0 or PP10 on gastric emptying was tested in 10 healthy volunteers and assessed using the 13 C breath test. Results are presented as mean ± SEM, and p < 0.05 was considered significant. For the IGP test, PP increased ingested nutrient volume: 886 ± 93, 1059 ± 124, and 1025 ± 125 ml for PP0, PP3, and PP10, respectively (p = 0.048). In all groups, Nadir IGP values were reached upon food intake (transformed values: 1.5 ± 0.2, 1.7 ± 0.3, and 1.6 ± 0.3 mmHg for PP0, PP3, and PP10, respectively; NS) to return to baseline thereafter. For the gastric emptying study, volunteers ingested a similar nutrient volume: 802 ± 119 and 1089 ± 128 ml (p = 0.016), and gastric half-emptying time was 281 ± 52 and 249 ± 37 min for PP0 and PP10, respectively (NS). No significant correlation between tolerated nutrient volume and IGP drop (R² < 0.01; p = 0.88 for PP0 vs. PP3 and R² =0.07; p = 0.40 for PP0 vs. PP10, respectively) or gastric half-emptying time (R² = 0.12; p = 0.32) was found. A supraphysiological PP dose enhances food tolerance; however, this effect is not mediated through gastric motility. CLINICAL TRIAL REGISTRY NUMBER: NCT03854708 is obtained from clinicaltrials.gov.

The effect of prucalopride on gastric sensorimotor function and satiation in healthy volunteers

BACKGROUND

Gastric motor function alterations have been implicated in the pathogenesis of functional dyspepsia with postprandial distress syndrome (PDS). Prucalopride, a 5-TH4 agonist, is known to stimulate gastrointestinal motility. We aimed to evaluate the effect of prucalopride on gastric sensorimotor function in healthy subjects (HV).

METHODS

Barostat and intragastric pressure (IGP) measurements were performed in 17 HV (59% females, age 29.4 ± 2.7 y) after treatment with placebo or prucalopride (2 mg) (single-blind cross-over). Isobaric stepwise distensions and gastric sensations were assessed to determine gastric compliance and sensitivity. Gastric accommodation (GA) with the barostat was quantified before and after ingestion of 200 ml of a nutrient drink (ND). GA measured by IGP was quantified as the drop of IGP from baseline during the intragastric infusion of ND until maximal satiation (60 ml/min).

KEY RESULTS

Prucalopride did not affect barostat assessed gastric compliance or sensitivity. No differences were observed in GA after prucalopride. During the barostat study, 10 min after the meal, 7 HVs reported significantly higher ratings for nausea after prucalopride (p < 0.001), and vomiting was induced in 4 of the HVs. A positive correlation was observed between the delta mean perception of nausea with the delta mean increase of intra-balloon volume before and after meal ingestion (r = 0.37, p = 0.03). During IGP measurements, no effect on nutrient tolerance was observed and increased cramp severity scores were observed which were associated with a significant increase of distal IGP (r = 0.78, p < 0.0001).

CONCLUSIONS & INFERENCES

Prucalopride does not enhances gastric accommodation but it might increase sensitivity to gastric distention. Furthermore, the increase in sensitivity seems to be related to an increase in nausea with distension. Clinicaltrials.gov: NCT04429802.

Impact of joint hypermobility syndrome on gastric accommodation and nutrient tolerance in functional dyspepsia

Functional dyspepsia (FD) is defined as the presence of gastroduodenal symptoms in the absence of organic disease that is likely to explain the symptoms. Joint hypermobility (JH) refers to the increased passive or active movement of a joint beyond its normal range and is characteristically present in patients with joint hypermobility syndrome (JHS), which is a hypermobile subtype of Ehlers-Danlos syndrome (EDS). Recent reports have highlighted the co-existence of FD with Ehlers-Danlos syndrome. Our aim was to study the prevalence of JHS in FD compared with healthy subjects and to study the impact of co-existing JHS on gastric motility, nutrient tolerance, and dyspeptic symptoms in FD.

METHODS

FD patients filled out a dyspepsia symptom severity score. Intragastric pressure (IGP) was measured with high-resolution manometry (HRM) during the intragastric infusion of nutrition drink (ND, 1.5 Kcal/ml, 60 ml/min) until maximal satiation in healthy subjects and FD. We compared IGP profiles and nutrient tolerance in HS and FD with or without JHS.

RESULTS

JHS was present in 54% of FD patients (n = 39, 41.2 ± 2.2 years old) and 7% of healthy subjects (n = 15, 27.3 ± 2.3 years old). IGP drop and nutrient tolerance were lower in non-JHS-FD compared with JHS-FD and HS (AUC JHS-FD: -17.9 ± 2.5 vs. non-JHS-FD: -13.0 ± 3.3 mmHg min, p = 0.2, HS:-19.6 ± 2.9 mmHg min; ND tolerance non-JHS-FD: 671.0 ± 96.0 vs. JHS-FD: 842.7 ± 105.7 Kcal, p = 0.25, HS: 980.0 ± 108.1 Kcal).

CONCLUSION

JHS often co-exists with FD. Non-JHS-FD was characterized by decreased accommodation and lower nutrient tolerance characterized compared with JHS-FD. Clinicaltrials.gov, reference number NCT04279990.

Nutrient Drinking Test as Biomarker in Functional Dyspepsia

INTRODUCTION

Functional dyspepsia (FD) is a prevalent condition with multifactorial pathophysiology, including impaired gastric accommodation (GA), hypersensitivity to gastric distention, and delayed gastric emptying. Drink tests (DT) have been proposed as a potential biomarker for the presence and severity of gastric sensorimotor dysfunction. Thus, we aimed to summarize the state of knowledge on different DT and their potential as a biomarker for FD.

METHODS

A PubMed and MEDLINE search was conducted for English language articles, reviews, meta-analyses, case series, and randomized controlled trials, including also published meeting abstracts.

RESULTS

Several DT have been described in literature (e.g., different type of liquid, number of calories used, pace of drinking, and subject's awareness of the amount of liquid drunk). FD patients ingest significantly less volume in the different variants of the tests. The slow nutrient ("satiety drinking") test (SDT) studies show the most consistent separation between health and FD and correlation with GA. However, sensitivity to distention may be correlated with rapid DT. SDTs were used to evaluate the effect of several pharmacological agents, often showing concordance between their effects on GA and tolerated nutrient volume. This correlation was not found mainly for agents with central actions.

DISCUSSION

An SDT is a potential diagnostic biomarker in FD, reflecting GA. Additional studies are required to confirm its role as a predictive biomarker for treatment outcome in FD.

The gastrointestinal tract in hunger and satiety signalling

BACKGROUND

Different peripheral pathways are implicated in the regulation of the food ingestion-digestion cycle.

METHODS

Narrative review on gastrointestinal mechanisms involved in satiety and hunger signalling.

RESULTS

Combined mechano- and chemoreceptors, peripherally released peptide hormones and neural pathways provide feedback to the brain to determine sensations of hunger (increase energy intake) or satiation (cessation of energy intake) and regulate the human metabolism. The gastric accommodation reflex, which consists of a transient relaxation of the proximal stomach during food intake, has been identified as a major determinant of meal volume, through activation of tension-sensitive gastric mechanoreceptors. Motilin, whose release is the trigger of gastric Phase 3, has been identified as the major determinant of return of hunger after a meal. In addition, the release of several peptide hormones such as glucagon-like peptide 1 (GLP-1), cholecystokinin as well as motilin and ghrelin contributes to gut-brain signalling with relevance to control of hunger and satiety. A number of nutrients, such as bitter tastants, as well as pharmacological agents, such as endocannabinoid receptor antagonists and GLP-1 analogues act on these pathways to influence hunger, satiation and food intake.

CONCLUSION

Gastrointestinal mechanisms such as gastric accommodation and motilin release are key determinants of satiety and hunger.

Duodenal acidification induces gastric relaxation and alters epithelial barrier function by a mast cell independent mechanism

Duodenal hyperpermeability and low-grade inflammation in functional dyspepsia is potentially related to duodenal acid exposure. We aimed to evaluate in healthy volunteers the involvement of mast cell activation on the duodenogastric reflex and epithelial integrity during duodenal acidification. This study consisted of 2 parts: (1) Duodenal infusion of acid or saline during thirty minutes in a randomized, double-blind cross-over manner with measurement of intragastric pressure (IGP) using high resolution manometry and collection of duodenal biopsies to measure epithelial barrier function and the expression of cell-to-cell adhesion proteins. Mast cells and eosinophils were counted and activation and degranulation status were assessed. (2) Oral treatment with placebo or mast cell stabilizer disodiumcromoglycate (DSCG) prior to duodenal perfusion with acid, followed by the procedures described above. Compared with saline, acidification resulted in lower IGP (P < 0.01), increased duodenal permeability (P < 0.01) and lower protein expression of claudin-3 (P < 0.001). Protein expression of tryptase (P < 0.001) was increased after acid perfusion. Nevertheless, an ultrastructural examination did not reveal degranulation of mast cells. DSCG did not modify the drop in IGP and barrier dysfunction induced by acid. Duodenal acidification activates an inhibitory duodenogastric motor reflex and, impairs epithelial integrity in healthy volunteers. However, these acid mediated effects occur independently from mast cell activation.

Targeting Treatment of Gastroparesis: Use of Clinical Tests to Guide Treatments

Gastroparesis presents with nausea, vomiting, and other upper gut symptoms, and is diagnosed by confirming delayed gastric emptying. A related condition, chronic unexplained nausea and vomiting, has similar symptoms but with normal emptying. Both conditions are managed using therapies with diverse mechanisms of action. Even though prokinetic treatments are proposed to improve gastroparesis by accelerating gastric emptying, there is limited evidence that they provide benefit by virtue of transit stimulating effects. Other tests can delineate alterations in other gut sensorimotor parameters in patients with suspected gastroparesis, but their relation to symptoms and their capability to guide treatment are largely unproved.

Small Bowel Dysmotility, Pseudoobstruction, and Functional Correlation with Histopathology: Lessons Learned

PURPOSE OF REVIEW

Small bowel dysmotility is a broad heterogeneous term that encompasses a wide range of gastrointestinal disorders resulting from abnormal gut motility. Chronic intestinal pseudo-obstruction (CIPO) is a severe, rare, and complex small bowel motility disorder at the extreme end of this spectrum. It is characterized by failure of the intestinal tract to propel contents, which results in signs and symptoms of bowel obstruction albeit in the absence of any obstructive lesion(s). In this article, we discuss up-to-date diagnostic techniques, management options, and histopathological findings in CIPO.

RECENT FINDINGS

We will emphasize the latest diagnostic methodologies and therapeutic options as well as enteric histopathologic abnormalities in patients with CIPO. CIPO continues to be a clinical challenge. Several novel pharmacological agents hold promise including gastrointestinal hormone agonists and prokinetics. Furthermore, histopathologic findings may help guide therapy and provide further prognostic significance. At present, nutritional support, symptom management, and avoidance of long-term complications are the mainstay of treatment in CIPO.

The effect of rikkunshito on gastrointestinal symptoms and gastric motor function: The first study in a Belgian functional dyspepsia population

BACKGROUND

Rikkunshito, a traditional Kampo medicine, has shown efficacy to treat functional dyspepsia (FD) in controlled trials in Japan. Its putative benefit for European patients and mechanism of action has not been established.

METHODS

This study examined the effect of rikkunshito on gastric motility and GI symptom perception in FD-PDS patients in a randomized, placebo-controlled, cross-over study. After a 2-week run-in period, patients received rikkunshito or matching placebo (2.5 g t.i.d.) for 4 weeks, separated by a 4-week washout period. Symptoms were assessed by the Leuven Postprandial Distress Scale (LPDS) diary throughout the study. At baseline and after both treatment arms, intragastric pressure (IGP) was measured to evaluate gastric accommodation and gastric motility. Simultaneously, GI symptoms were scored on a 100 mm visual analogue scale. Validated symptom questionnaires (PAGI-SYM, VSI, DSS, and PHQ) were completed each study visit.

KEY RESULTS

Twenty-three patients completed the study (33 ± 14 years, 22.7 ± 3.22 kg/m² ). Intragastric pressure was numerically, but not significantly, lower after rikkunshito compared with baseline and placebo (P = .14). No differences were found in gastric accommodation, nutrient volume tolerance, and symptoms assessed during IGP measurements. Early satiation and postprandial fullness (daily diary) decreased after rikkunshito compared with baseline (P < .041 for both). Placebo also improved most other symptoms assessed. No significant changes in VSI scores occurred. No adverse reactions occurred.

CONCLUSIONS

Rikkunshito did not alter gastric motility. Treatment with rikkunshito improved upper GI symptoms in FD patients but similarly high placebo effects were observed using the LPDS diary, PAGI-SYM, SF-NDI, and DSS scores. Rikkunshito was safe and well-tolerated.

Biomechanical and microstructural characterisation of the porcine stomach wall: Location- and layer-dependent investigations

The mechanical properties of the stomach wall help to explain its function of storing, mixing, and emptying in health and disease. However, much remains unknown about its mechanical properties, especially regarding regional heterogeneities and wall microstructure. Consequently, the present study aimed to assess regional differences in the mechanical properties and microstructure of the stomach wall. In general, the stomach wall and the different tissue layers exhibited a nonlinear stress-stretch relationship. Regional differences were found in the mechanical response and the microstructure. The highest stresses of the entire stomach wall in longitudinal direction were found in the corpus (201.5 kPa), where food is ground followed by the antrum (73.1 kPa) and the fundus (26.6 kPa). In contrast, the maximum stresses in circumferential direction were 39.7 kPa, 26.2 kPa, and 15.7 kPa for the antrum, fundus, and corpus, respectively. Independent of the fibre orientation and with respect to the biaxial loading direction, partially clear anisotropic responses were detected in the intact wall and the muscular layer. In contrast, the innermost mucosal layer featured isotropic mechanical characteristics. Pronounced layers of circumferential and longitudinal muscle fibres were found in the fundus only, whereas corpus and antrum contained almost exclusively circumferential orientated muscle fibres. This specific stomach structure mirrors functional differences in the fundus as well as corpus and antrum. Within this study, the load transfer mechanisms, connected with these wavy layers but also in total with the stomach wall's microstructure, are discussed. STATEMENT OF SIGNIFICANCE: This article examines for the first time the layer-specific mechanical and histological properties of the stomach wall attending to the location of the sample. Moreover, both mechanical behaviour and microstructure were explicitly match identifying the heterogeneous characteristics of the stomach. On the one hand, the results of this study contribute to the understanding of stomach mechanics and thus to their functional understanding of stomach motility. On the other hand, they are relevant to the fields of constitutive formulation of stomach tissue, whole stomach mechanics, and stomach-derived scaffolds i.e., tissue-engineering grafts.

Current and emerging therapeutic options for the management of functional dyspepsia

Introduction: Functional Dyspepsia (FD), defined as chronic symptoms originating from the gastroduodenal region in absence of readily identifiable organic disease, is one of the most common gastrointestinal disorders. FD is divided into two subgroups: Post-Prandial Distress Syndrome (PDS) or meal-related FD, characterized by postprandial fullness and early satiation, and Epigastric Pain Syndrome (EPS) or meal-unrelated FD, characterized by epigastric pain and burning.Areas covered: This review summarizes the existing and off-label therapeutic options for FD.Expert opinion: The identification of mechanisms, the Rome IV classification, the reduction of PDS/EPS overlap and pictograms for symptom identification allow a better diagnosis and a more targeted treatment choice. Acotiamide, a first-in-class prokinetic agent available only in Japan and India, is the only agent of proven efficacy for FD, but clinicians use acid-suppressive therapy, prokinetics, neuromodulators and herbal therapies for treating FD symptoms. New emerging targets are duodenal low-grade inflammation with eosinophils and duodenal or other modified luminal microbiota.

Duodenal nutrient exposure contributes to enhancing gastric accommodation

BACKGROUND

The gastric accommodation reflex consists of a relaxation which creates a reservoir for the ingested food before emptying to the duodenum occurs. The mechanisms that control gastric accommodation are not fully understood. This study aims to use intragastric pressure (IGP) measurement and pyloric balloon obstruction to determine the contribution of duodenal nutrient exposure to gastric accommodation and meal-induced satiation.

METHODS

Two conditions were tested in 11 healthy subjects (28.3 ± 3.2 years; 23.6 ± 0.7 kg/m² ; four females). IGP was measured during an intragastric nutrient drink (ND) infusion at a constant rate (60 mL/min) in the presence of a deflated (control) or inflated (pyloric obstruction) balloon placed into the pylorus. During the study, subjects filled out Likert scales for satiation scores and visual analogue scale for 9 epigastric symptoms (hunger, expected amount to eat, satiation, bloating, fullness, nausea, belching, gastric cramps, and pain) before and during ND infusion until maximal satiation.

KEY RESULTS

During pyloric obstruction, the IGP drop and the area above the IGP curve (AAC) were significantly smaller compared with the control condition (6.7 ± 1.0 mm Hg vs3.6 ± 0.8 mm Hg, P = .03 and 69.7 ± 13.5 mm Hg × min vs 20.1 ± 9.0 mm Hg × min, P = .001, respectively). Pyloric obstruction decreased nutrient tolerance compared with the control condition (787.9 ± 73.1 mL vs 970.9 ± 79.2 mL, respectively, P < .05). Pyloric obstruction increased symptoms of bloating (1.3 ± 0.4 vs 2.6 ± 0.6; P = .04), fullness (2.3 ± 0.5 vs 3.6 ± 0.3; P = .03), and nausea (0.4 ± 0.2 vs 1.3 ± 0.4; P = .04) compared to control.

CONCLUSION & INFERENCES

Duodenal nutrient exposure contributes to enhancing gastric accommodation. Preventing the passage of nutrients from the stomach to the duodenum inhibits gastric accommodation and increases meal-induced satiation, bloating, nausea, and fullness.

Development of a Gastric Simulation Model (GSM) incorporating gastric geometry and peristalsis for food digestion study

There has been growing interest in developing in vitro gastrointestinal models as alternatives to in vivo tests, which is challenging ethically and financially. An in vitro Gastric Simulation Model (GSM) was developed to reproduce the geometry and motility of human stomach. The peristalsis was generated by a series of syringes squeezing a latex chamber pneumatically. In particular, the distribution, amplitude and frequency of contractions demonstrated similar patterns as in human gastric conditions. The breakdown kinetics and size distribution of sausage particles during the digestion were investigated in GSM to demonstrate the effect of the contraction force. Furthermore, the gastric emptying of water-soluble nutrient (methylene blue) and nondigestible solids (amberlite beads) was investigated. The results indicated that the viscosity of the gastric digesta significantly affected the local flow and emptying behavior of nutrients and solids. This study illustrated the capability of GSM to recreate the transient physiological conditions and dynamic flow of gastric contents due to its specificity of geometry and contraction patterns. The new model can be used to investigate the influence of food matrix and physiological conditions, including gastric secretion and contraction forces on transit and digestion of foods in the stomach.

Effect of citalopram on esophageal motility in healthy subjects-Implications for reflux episodes, dysphagia, and globus

BACKGROUND

Drugs such as citalopram, "targeting" the serotonin pathway, can alter esophageal mechano-chemical sensitivity and gastrointestinal motility. The aim of this study was to clarify the effect of citalopram on esophageal motility and sphincter function, transient lower esophageal sphincter relaxations (TLESRs), and reflux events.

METHODS

Sixteen healthy volunteers (HV) receiving 20 mg citalopram or placebo intravenously, in a randomized cross-over fashion, underwent two high-resolution impedance manometry studies involving liquid swallows and a high-fat, high-caloric meal. Manometric, reflux, and symptom-related parameters were studied.

KEY RESULTS

A lower distal contractile integral was recorded under citalopram, compared with placebo (P = 0.026). Upper esophageal sphincter (UES) resting pressure was significantly higher after citalopram administration throughout the study (P < 0.05, all periods). Similarly, the UES postswallow mean and maximum pressures were higher in the citalopram condition (P < 0.0001, in both cases) and this was also the case for the 0.2 s integrated relaxation pressure (P = 0.04). Esophagogastric junction resting pressures in the citalopram visit were significantly higher during swallow protocol, preprandial period, and the first postprandial hour (P < 0.05, in all cases). TLESRs and total reflux events were both reduced after citalopram infusion (P = 0.01, in both cases). During treatment with citalopram, five participants complained about globus sensation (P = 0.06). This citalopram-induced globus was associated with higher UES postswallow mean and maximum pressure values (P = 0.01 and P = 0.04, respectively).

CONCLUSIONS AND INFERENCES

Administration of citalopram exerts a diversified response on esophageal motility and sphincter function, linked to clinically relevant phenomena: a reduction in postprandial TLESRs and the induction of drug-induced globus.

Gastric accommodation measurements by single photon emission computed tomography and two-dimensional scintigraphy in diabetic patients with upper gastrointestinal symptoms

OBJECTIVE

To compare estimates of gastric accommodation (GA) with single photon emission computed tomography (SPECT) to measurements based on intragastric meal distribution immediately post-meal ingestion (IMD⁰ ).

METHODS

We evaluated 108 diabetics with upper gastrointestinal (UGI) symptoms who had undergone gastric emptying of solids (GE) by scintigraphy and GA measurements by SPECT. Immediately after ingestion of a ^99m Tc-labeled egg meal (time 0), we estimated IMD⁰ as radioactive counts or area of the proximal half of the stomach on two-dimensional images. Gastric volume (GV) during fasting and after 300 mL Ensure^® was measured by SPECT to quantify accommodation volume (AV) or postprandial to fasting volume ratio (GVR). From the measured proximal gastric area, we estimated the volume of proximal stomach (4/3 × π × r³ ). We performed regression analyses to assess relationships between IMD⁰ and GA (AV) and GVR.

RESULTS

There was a significant correlation between area and radioactivity counts in the proximal stomach (r = 0.67, P < 0.001); however, there was considerable interpersonal variation [bias 0.20 (95% CI -0.07, 0.47)]. There were no significant correlations between total GV or AV or VR by SPECT and measurements using IMD⁰ : proximal gastric counts, area, and estimated volume as continuous variables of dichotomized patient groups, based on published cutoff values. There were no significant differences in total gastric area or the IMD⁰ parameters (% area or % radioactive counts) between those with and without UGI symptoms except for fullness and satiety.

CONCLUSIONS

Intragastric meal distribution immediately post-meal ingestion is not significantly correlated with GA measurement by SPECT.

Randomised clinical trial: the DPP-4 inhibitor, vildagliptin, inhibits gastric accommodation and increases glucagon-like peptide-1 plasma levels in healthy volunteers

BACKGROUND

Dipeptidyl peptidase-4 (DPP-4) inactivates glucagon-like peptide-1 (GLP-1). Whether DPP-4 inhibition affects GLP-1 metabolism and/or food intake in humans remains unknown.

AIMS

To evaluate the effect of vildagliptin (DPP-4 inhibitor) on gastric accommodation and ad libitum food intake in healthy volunteers (HVs) METHODS: The effects of acute oral vildagliptin administration (50 mg) were evaluated in two randomised, placebo-controlled, single-blinded trials. Protocol 1 (n = 10, 32.3 ± 3 years, 23.4 ± 0.7 kg/m² ): 60 min after treatment, a nutrient drink (270 kcal) was infused intragastrically and intragastric pressure (IGP) was measured for 1 h. Protocol 2 (n = 10, 24.3 ± 0.8 years, 22.3 ± 0.9 kg/m² ): 60 min after treatment, HVs consumed one nutrient drink (300 kcal). Thirty minutes thereafter, HVs ate ad libitum from a free-choice buffet for 30 min. Blood was collected at several time points to measure active GLP-1 plasma levels.

RESULTS

During the first 20 min after nutrient infusion, the drop in IGP was smaller after vildagliptin compared to placebo (treatment-by-time interaction effect: P = 0.008). No differences were seen on epigastric symptom scores. Planned contrast analysis showed that active GLP-1 levels were higher after vildagliptin compared to placebo (P = 0.018) only after nutrient ingestion. Total food intake (316.38 ± 58.89 g vs 399.58 ± 63.02 g, P = 0.359) and total caloric intake (594.77 ± 115.17 kcal vs 742.77 ± 107.10 kcal, P = 0.371) did not differ between treatments.

CONCLUSIONS

Vildagliptin inhibits gastric accommodation without affecting epigastric symptom scoring in HVs. Active GLP-1 plasma levels were increased after vildagliptin treatment, but the increase was not sufficient to affect ad libitum food intake. The study was registered at Clincialtrials.gov (NCT 03500900).

Acotiamide affects antral motility, but has no effect on fundic motility, gastric emptying or symptom perception in healthy participants

BACKGROUND

Acotiamide, a prokinetic agent was shown to be efficacious in the treatment of functional dyspepsia (FD). The exact mechanism of action is incompletely elucidated.

METHODS

This randomized, placebo-controlled, cross-over study aimed to examine the effect of acotiamide on gastric motility, measured as intragastric pressure, gastric emptying (GE) rate and gastrointestinal (GI) symptom perception in healthy volunteers (HVs). Participants were treated with acotiamide (100 mg tid) and placebo for 3 weeks, separated by a 1-week washout period. A daily symptom diary was collected during both treatments. At the end of each treatment period, GE rate and gastric motility were assessed with a ¹³ C-octanoic acid breath test and high-resolution manometry during nutrient infusion, respectively. GI symptom levels were scored during high-resolution manometry. Data were analyzed using mixed models. The study was registered as NCT03402984.

KEY RESULTS

Twenty HVs (10 female, 25 ± 4.1 years, 22.58 ± 2.73 kg/m² ) participated in the study. There was no difference in GE half time between both treatments (P = 0.92). Acotiamide had no effect on fundic pressures before and after nutrient infusion (P = 0.91). However, postprandial antral pressures remained significantly lower compared to placebo (P = 0.015). There was no significant difference in hunger, satiation and GI symptoms scores assessed during IGP measurement and by the daily diary (P > 0.12 for all).

CONCLUSION

Acotiamide is associated with lower antral pressures after nutrient intake, whereas it has no effect on fundic pressures, GE rate and symptom perceptions in HVs. Studies in FD need to elucidate whether lower antral pressures induced by acotiamide underlie postprandial symptom improvement in FD.

GI Motility Testing: Stomach, Small Bowel, and Colon

Symptoms of abdominal pain, nausea, vomiting, bloating, abdominal distention, diarrhea, and constipation are common and may relate to abnormalities in gastrointestinal motility. There are a number of different options to study gastrointestinal motility. This article reviews novel and standard motility tests available in the stomach, small bowel, and colon. The indications for testing, technical details, advantages, and disadvantages of each test will be summarized.

Computational Models for the Mechanical Investigation of Stomach Tissues and Structure

Bariatric surgery is performed on obese people aiming at reducing the capacity of the stomach and/or the absorbing capability of the gastrointestinal tract. A more reliable and effective approach to bariatric surgery may integrate different expertise, in the areas of surgery, physiology and biomechanics, availing of a strong cooperation between clinicians and engineers. This work aimed at developing a computational model of the stomach, as a computational tool for the physio-mechanical investigation of stomach functionality and the planning of bariatric procedures. In this sense, coupled experimental and numerical activities were developed. Experimental investigations on pig and piglet stomachs aimed at providing information about stomach geometrical configuration and structural behavior. The computational model was defined starting from the analysis of data from histo-morphometric investigations and mechanical tests. A fiber-reinforced visco-hyperelastic constitutive model was developed to interpret the mechanical response of stomach tissues; constitutive parameters were identified considering mechanical tests at both tissue and structure levels. Computational analyses were performed to investigate the pressure-volume behavior of the stomach. The developed model satisfactorily interpreted results from experimental activities, suggesting its reliability. Furthermore, the model was exploited to investigate stress and strain fields within gastric tissues, as the stimuli for mechanoreceptors that interact with the central nervous system leading to the feeling of satiety. In this respect, the developed computational model may be employed to evaluate the influence of bariatric intervention on the stimulation of mechanoreceptors, and the following meal induced satiety.

Evaluation of Patients with Suspected Gastroparesis

There is substantial overlap between the symptoms of gastroparesis and a variety of alternative disorders. These conditions include rumination syndrome, drug-induced gastric emptying delay, cannabinoid hyperemesis syndrome, and eating disorders, which can be identified based on the history alone. The remaining patients require a diagnostic approach of physical examination, laboratory tests, evaluation with esophagogastroduodenoscopy or contrast radiography, and a test to measure gastric emptying. Symptomatic patients who have normal nutritional status and gastric emptying that is either normal or mildly delayed should be diagnosed with functional dyspepsia, whereas patients with moderate or severe gastric emptying delay are diagnosed with gastroparesis.

Postprandial distress syndrome: stratification and management

Functional dyspepsia (FD), defined by the Rome consensus as the presence of functional symptoms originating from the gastroduodenum, is one of the most common functional gastrointestinal disorders. FD is subdivided into postprandial distress syndrome (PDS), with meal-related symptoms such as postprandial fullness and early satiation, and epigastric pain syndrome (EPS), with meal-unrelated symptoms such as epigastric pain or burning. We used a literature search for a narrative review on the current state of knowledge regarding PDS. Areas covered: Epidemiological studies support PDS as a separate entity and the biggest FD subgroup. The pathophysiology of PDS is heterogeneous, and disorders of gastric sensorimotor function as well as low grade duodenal inflammation have been implicated. Although prokinetic agents may provide the most pathophysiology-oriented treatment option, there is a paucity of suitable agents, and proton pump inhibitors are the traditional first-line therapy. Other options include agents that enhance gastric accommodation, such as acotiamide and 5-HT_1A agonists, neuromodulators such as mirtazapine, and traditional medicine approaches. Expert commentary: PDS is highly prevalent, with probably heterogeneous underlying pathophysiology. Motility modifying agents and neuromodulators are the cornerstone of PDS therapy, but there is a need for high quality studies of new therapeutic approaches.

New developments in the treatment of gastroparesis and functional dyspepsia

Functional dyspepsia (FD) and gastroparesis are frequent causes of upper gastrointestinal symptoms such as postprandial fullness, early satiation, epigastric pain or burning, upper abdominal bloating, bothersome belching, nausea and vomiting. The underlying pathophysiological mechanisms are heterogeneous and involved mechanisms such as abnormal gastric motility (accommodation, emptying), visceral hypersensitivity, low grade mucosal inflammation and cellular changes in enteric nerves, muscle or interstitial cells of Cajal. Patient-reported outcomes for evaluating treatment efficacy in these conditions were recently developed and validated. Prokinetic agents, which enhance gastric motility, are used for treating both gastroparesis and FD. In FD, besides acid suppressive therapy and Helicobacter pylori eradication, neuromodulators and drugs that enhance gastric accommodation can be applied. In gastroparesis, anti-emetics may also provide symptom relief. Novel approaches under evaluation in these conditions are the fundus relaxing agents acotiamide and buspirone and the antidepressant mirtazapine in FD. For gastroparesis, recently studied agents include the prokinetic ghrelin agonist relamorelin, the prokinetic serotonergic agents velusetrag and prucalopride, the anti-emetic aprepitant and per-endoscopic pyloric myotomy procedures.

Expert consensus document: Advances in the diagnosis and classification of gastric and intestinal motility disorders

Disturbances of gastric, intestinal and colonic motor and sensory functions affect a large proportion of the population worldwide, impair quality of life and cause considerable health-care costs. Assessment of gastrointestinal motility in these patients can serve to establish diagnosis and to guide therapy. Major advances in diagnostic techniques during the past 5-10 years have led to this update about indications for and selection and performance of currently available tests. As symptoms have poor concordance with gastrointestinal motor dysfunction, clinical motility testing is indicated in patients in whom there is no evidence of causative mucosal or structural diseases such as inflammatory or malignant disease. Transit tests using radiopaque markers, scintigraphy, breath tests and wireless motility capsules are noninvasive. Other tests of gastrointestinal contractility or sensation usually require intubation, typically represent second-line investigations limited to patients with severe symptoms and are performed at only specialized centres. This Consensus Statement details recommended tests as well as useful clinical alternatives for investigation of gastric, small bowel and colonic motility. The article provides recommendations on how to classify gastrointestinal motor disorders on the basis of test results and describes how test results guide treatment decisions.

Gastric accommodation in healthy subjects studied by ultrasound, manometry, and impedancemetry

BACKGROUND

Gastric accommodation to a meal may be important in the pathogenesis of upper gastrointestinal disorders, but has been difficult to investigate in a minimally invasive fashion.

METHODS

We studied gastric and lower esophageal physiology during food intake, combining transabdominal ultrasound, multichannel high-resolution impedance-manometry (HRIM) and a symptom questionnaire. A HRIM catheter was distally positioned at incisura angularis and 300 mL saline with 75 g glucose was ingested. Target variables were recorded for 30 min after fluid intake.

KEY RESULTS

Fifteen healthy subjects' participated (11W/4M, median age 23.8 y) and all accepted the meal with few symptoms. At incisura angularis maximum change in pressure from pre-intake values was -7.4 mmHg after 60 s (P < .0001), rising to pre-intake values within 20 min. The corresponding area increased significantly from pre-intake values of 8.0 cm² to 14.1 cm² shortly after intake (P = .0012), peaked at 5 min and slowly decreased towards 30 min. The corresponding maximum change in stress from pre-intake pressure values was -59.2 mmHg shortly after (P < .0001), reaching pre-intake values within 20 min. Strain rose from 0 shortly before to 0.36 shortly after (P < .0001), peaking at 5 min. At incisura angularis, fullness was positively correlated with area and to strain, while fullness, area, and stress were negatively correlated with pressure.

CONCLUSIONS & INFERENCES

The multimodal method enabled assessment of the gastric accommodation reflex, stress and strain in the stomach. It triggered few symptoms in healthy volunteers. We propose it to be a more physiological replacement of the barostat technique.

The effect of sildenafil on gastric motility and satiation in healthy controls

Sildenafil induces relaxation of smooth muscle cells by blocking PDE5. Dyspepsia is one of sildenafil's most frequently reported adverse events, suggesting its effect on gastric motility. Our aim was to study the effect of sildenafil on gastric accommodation (GA) and gastric emptying (GE) in healthy volunteers (HVs).

Methods

Sildenafil (50 mg) or placebo was randomly administered to 16 blinded HVs. After a manometry probe and an infusion catheter were positioned in the proximal stomach, the intragastric pressure (IGP) was measured before and during nutrient drink infusion (ND, 60 ml/min). HVs were asked to score their hunger, satiation and six epigastric symptoms at five-minute intervals. The experiment ended when the HVs scored maximal satiation during ND infusion at one-minute intervals. To assess GE, breath samples were collected every 15 minutes for six hours after the meal (244 kcal).

Results

ND infusion induced a drop in proximal stomach IGP, which was suppressed by sildenafil (average area under the curve for sildenafil: -33.6 ± 8.8 mmHg; placebo: -60.8 ± 11.3 mmHg, p = 0.005). Sildenafil-treated volunteers reached earlier maximal satiation compared to placebo (678 ± 70 ml vs. 836 ± 82.6 ml, p = 0.019). Finally, GE was significantly slower after sildenafil (90.6 ± 5.9 min vs. 76.6 ± 7.1 min, p = 0.04).

Conclusion

Sildenafil inhibits GA, leading to significantly decreased nutrient tolerance, and slightly delays the GE rate in humans.

Effect of intragastric FODMAP infusion on upper gastrointestinal motility, gastrointestinal, and psychological symptoms in irritable bowel syndrome vs healthy controls

BACKGROUND

The low fermentable oligo-, di-, mono-saccharides and polyol (FODMAP) diet is a treatment strategy to reduce symptoms of irritable bowel syndrome (IBS). Acute effects of FODMAPs on upper gastrointestinal motility are incompletely understood. Our objectives were to assess the acute effects of intragastric FODMAP infusions on upper gastrointestinal motility and gastrointestinal and psychological symptoms in healthy controls (HC) and IBS patients.

METHODS

A high-resolution solid-state manometry probe and an infusion tube were positioned into the stomach. Fructans, fructose, FODMAP mix, or glucose was intragastrically administered to HC, and fructans or glucose was administered to IBS patients until full satiation (score 0-5), in a randomized crossover fashion. Manometric measurements continued for 3 hours. Gastrointestinal and psychological symptoms were assessed by questionnaires at predefined time points. The study was registered on www.clinicaltrials.gov (NCT02980406).

KEY RESULTS

Twenty HC and 20 IBS patients were included. Fructans induced higher postprandial gastric pressures compared with glucose over both groups (P<.001). Bloating, belching, and pain increased more in IBS over both carbohydrates (P<.041). In addition, IBS patients reported more flatulence and cramps compared with HC following fructans (P<.001). Glucose induced more fatigue and dominance compared with fructans (P=.028, P=.001). Irritable bowel syndrome patients reported a higher increase in anger (P=.030) and a stronger decrease in positive affect (P=.021).

CONCLUSIONS & INFERENCES

The upper gastrointestinal motility response varies between carbohydrates. Irritable bowel syndrome patients are more sensitive to fructan infusion, reflected in their higher gastrointestinal symptom scores. Acute carbohydrate infusion can have differential psychological effects in IBS and HC.

The effect of mirtazapine on gastric accommodation, gastric sensitivity to distention, and nutrient tolerance in healthy subjects

BACKGROUND

Disturbances of gastric motor function of functional dyspepsia (FD) have been implicated in the pathogenesis of the symptoms, and hence, motility modifying agents are considered for its treatment. Mirtazapine was recently shown to improve symptoms and increase nutrient tolerance in FD patients with weight loss. We aim to evaluate the effect of mirtazapine on gastric sensorimotor function in healthy volunteers (HV).

METHODS

Thirty-one HV underwent an intragastric pressure (IGP) and barostat measurements on separate days before and after 3 weeks of placebo or mirtazapine (15 mg). Gastric compliance, sensitivity and accommodation (GA) measured by the barostat. GA was quantitated as the difference (delta) in intra-balloon volume before and after ingestion of 200 mL of a nutrient drink (ND). GA measured by IGP was quantitated as the drop of IGP from baseline during the intragastric infusion of ND until maximal satiation.

KEY RESULTS

Mirtazapine significantly increased the bodyweight of subjects (67.8±3.7 to 69.1±3.7 kg; P=.01). Barostat results showed no effect on gastric compliance, sensitivity, and GA. Nutrient tolerance was not affected after treatment (1170±129.4 vs 1104±133.6 kcal; P=.4), and mirtazapine was associated with lower symptom ratings. The IGP drop during meal ingestion was significantly suppressed (area under the curve: -43.3±4.5 mm Hg vs -28.9±3.1 mm Hg; P=.005).

CONCLUSIONS & INFERENCES

In HVs, the occurrence of weight gain and decreased meal-induced symptoms in spite of a suppressed meal-induced IGP drop, point towards a central mode of action. Mirtazapine does not display changes in gastric sensorimotor function that could explain its beneficial effects on symptoms and nutrient tolerance in FD.

Severely impaired gastric accommodation is a hallmark of post-Nissen functional dyspepsia symptoms

BACKGROUND

Laparoscopic Nissen fundoplication is a commonly performed antireflux surgery, after which reflux symptoms are well controlled, however, complications such as inability to belch or dyspeptic symptoms (mimicking those of functional dyspepsia [FD]) might occur. The aim of the study was to prospectively evaluate symptom pattern and underlying pathophysiological mechanisms in patients with post-Nissen dyspepsia.

METHODS

Twenty-four patients (12 f, mean age 44.5±2.8 years) with post-Nissen dyspepsia symptoms, five patients (3 f, mean age 38.8±3.2 years) with post-Nissen dysphagia symptoms and 14 pre-fundoplication patients (3 f, mean age 42.1±2.5 years) were evaluated. Patients filled out a Rome II-based dyspepsia symptom severity score, performed a gastric emptying test, and a gastric barostat study was used to evaluate the function of the proximal stomach.

KEY RESULTS

Upper abdominal bloating scores were higher in post-Nissen dyspepsia patients (P=.016) and symptoms of postprandial distress syndrome (PDS) were more present in post-Nissen dyspepsia patients compared to the other two groups (P=.07). Weight loss was significantly higher in the post-Nissen groups compared to the pre-fundoplication (P=.02). Gastric emptying rates were similar in the three groups. Gastric accommodation (GA) was significantly impaired in the post-Nissen dyspepsia group (dyspepsia -30[-86-83] vs dysphagia 163[148-203] vs pre-fundoplication 147[75-174] mL, P=.004) and the prevalence of patients with impaired GA was higher in the post-Nissen group (P=.007). Postprandial fullness was more prevalent in patients with impaired GA compared to those with normal GA (P=.01).

CONCLUSIONS AND INTERFERENCES

Patients with post-Nissen dyspepsia show a symptom pattern similar to that in FD patients with PDS, and the main underlying mechanism seems to be impaired gastric accommodation to a meal.

White Paper AGA: Functional Dyspepsia

Functional dyspepsia remains a major challenge for clinicians with no approved drugs available in the Western World. In October 2016, a meeting was held in Washington, DC, sponsored by the American Gastroenterological Association's Center for Diagnostics and Therapeutics, which included members of the Food and Drug Administration (FDA) and the pharmaceutical industry, experts in FD, and representatives of patient organizations. This white paper summarizes our current status, progress with a validated patient reported outcome instrument in functional dyspepsia, future directions and needs.

The Intragastric Pressure Measurement: A Novel Method to Assess Gastric Accommodation in Functional Dyspepsia Children

BACKGROUND

Impaired gastric accommodation (GA) is proposed as a main pathophysiological mechanism for functional dyspepsia (FD). At present, the gastric barostat is the criterion standard to measure GA. Hence, this procedure is invasive and it may alter gastric physiology. Recently, we proposed the measurement of intragastric pressure (IGP) by means of high-resolution manometry during nutrient intake as a potential alternative for assessing GA in adults.

OBJECTIVES

Our aim was first to study the feasibility of the IGP measurement with nutrient tolerance in children with FD and second to compare these results with young healthy adults.

METHODS

A high-resolution manometry probe and a feeding tube were positioned in the proximal stomach. The IGP was measured before and during intragastric infusion of a nutrient drink (ND, 300 kcal, 60 mL/min). Subjects were asked to score their satiation and epigastric symptoms. The test ended when the subjects scored maximal satiation.

RESULTS

A total of 15 healthy volunteers (HVs, 21.7 ± 4.7 years, 21.1 ± 0.3 kg/m) and 17 patients with FD (14.4 ± 0.7 years, 19.6 ± 0.7 kg/m) participated. Patients with FD experienced mainly from postprandial fullness (86%), epigastric pain (71%), and bloating (62%). In both groups, intragastric infusion of ND induced a drop in IGP (area above the IGP curve FD: -15.5 ± 3.5 mmHg vs HVs: -18.0 ± 8.7 mmHg; P = 0.57). Patients showed impaired nutrient tolerance compared with HVs (587.6 ± 80.2 vs 936 ± 66.2 kcal; P = 0.003). All patients and HVs tolerated the catheters and could finalize the study.

CONCLUSIONS

The measurement of IGP during intragastric ND infusion was well tolerated in children. Nutrient tolerance was reduced in children with FD compared with HVs. In the future, this may be a useful tool to assess GA accommodation and nutrient tolerance in children.

Functional Dyspepsia and Gastroparesis

BACKGROUND

Upper gastrointestinal disorders typically present with common symptoms. The most relevant non-mucosal diseases are gastroparesis, functional dyspepsia and rumination syndrome. The literature pertaining to these 3 conditions was reviewed.

KEY MESSAGES

Gastroparesis is characterized by delayed gastric emptying in the absence of mechanical obstruction of the stomach. The cardinal symptoms include postprandial fullness (early satiety), nausea, vomiting and bloating. The most frequently encountered causes of these symptoms are mechanical obstruction (pyloric stenosis), iatrogenic disease, gastroparesis, functional dyspepsia, cyclical vomiting and rumination syndrome. The most common causes of gastroparesis are neuropathic disorders such as diabetes, idiopathic, post-vagotomy and scleroderma among myopathic disorders. Principles of management of gastroparesis include exclusion of mechanical obstruction with imaging and iatrogenic causes with careful medication and past surgical history. Prokinetics and anti-emetics are the mainstays of treatment. Functional dyspepsia is characterized by the same symptoms as gastroparesis; in addition to delayed gastric emptying, pathophysiological abnormalities include accelerated gastric emptying, impaired gastric accommodation and gastric or duodenal hypersensitivity to distension and nutrients. Novel treatments include tricyclic antidepressants in patients with normal gastric emptying, acotiamide (acetyl cholinesterase inhibitor) and 5-HT1A receptor agonists such as buspirone. Rumination syndrome is characterized by repetitive regurgitation of gastric contents occurring within minutes after a meal. Episodes often persist for 1-2 h after the meal, and the regurgitant consists of partially digested food that is recognizable in its taste. Regurgitation is typically effortless or preceded by a sensation of belching. This has been summarized as a 'meal in, meal out, day in, day out' behavior for weeks or months, differentiating rumination from gastroparesis. Patients often have a background of psychological disorder or a prior eating disorder. Treatment is based on behavioral modification.

CONCLUSION

Precise identification of the cause and pathophysiology of upper gastrointestinal symptoms is essential for optimal management.

Measurement of Gastrointestinal and Colonic Motor Functions in Humans and Animals

Accurately measuring the complex motor behaviors of the gastrointestinal tract has tremendous value for the understanding, diagnosis and treatment of digestive diseases. This review synthesizes the literature regarding current tests that are used in both humans and animals. There remains further opportunity to enhance such tests, especially when such tests are able to provide value in both the preclinical and the clinical settings.

Pharmacological, Pharmacokinetic, and Pharmacogenomic Aspects of Functional Gastrointestinal Disorders

This article reviews medications commonly used for the treatment of patients with functional gastrointestinal disorders. Specifically, we review the animal models that have been validated for the study of drug effects on sensation and motility; the preclinical pharmacology, pharmacokinetics, and toxicology usually required for introduction of new drugs; the biomarkers that are validated for studies of sensation and motility endpoints with experimental medications in humans; the pharmacogenomics applied to these medications and their relevance to the FGIDs; and the pharmacology of agents that are applied or have potential for the treatment of FGIDs, including psychopharmacologic drugs.

Motilin-induced gastric contractions signal hunger in man

RATIONALE

Hunger is controlled by the brain, which receives input from signals of the GI tract (GIT). During fasting, GIT displays a cyclical motor pattern, the migrating motor complex (MMC), regulated by motilin.

OBJECTIVES

To study the relationship between hunger and MMC phases (I-III), focusing on spontaneous and pharmacologically induced phase III and the correlation with plasma motilin and ghrelin levels. The role of phase III was also studied in the return of hunger after a meal in healthy individuals and in patients with loss of appetite.

FINDINGS

In fasting healthy volunteers, mean hunger ratings during a gastric (62.5±7.5) but not a duodenal (40.4±5.4) phase III were higher (p<0.0005) than during phase I (27.4±4.7) and phase II (37±4.5). The motilin agonist erythromycin, but not the cholinesterase inhibitor neostigmine, induced a premature gastric phase III, which coincided with an increase in hunger scores from 29.2±7 to 61.7±8. The somatostatin analogue octreotide induced a premature intestinal phase III without a rise in hunger scores. Hunger ratings significantly correlated (β=0.05; p=0.01) with motilin plasma levels, and this relationship was lost after erythromycin administration. Motilin, but not ghrelin administration, induced a premature gastric phase III and a rise in hunger scores. In contrast to octreotide, postprandial administration of erythromycin induced a premature gastric phase III accompanied by an early rise in hunger ratings. In patients with unexplained loss of appetite, gastric phase III was absent and hunger ratings were lower.

CONCLUSIONS

Motilin-induced gastric phase III is a hunger signal from GIT in man.

The stomach in health and disease

The stomach is traditionally regarded as a hollow muscular sac that initiates the second phase of digestion. Yet this simple view ignores the fact that it is the most sophisticated endocrine organ with unique physiology, biochemistry, immunology and microbiology. All ingested materials, including our nutrition, have to negotiate this organ first, and as such, the stomach is arguably the most important segment within the GI tract. The unique biological function of gastric acid secretion not only initiates the digestive process but also acts as a first line of defence against food-borne microbes. Normal gastric physiology and morphology may be disrupted by Helicobacter pylori infection, the most common chronic bacterial infection in the world and the aetiological agent for most peptic ulcers and gastric cancer. In this state-of-the-art review, the most relevant new aspects of the stomach in health and disease are addressed. Topics include gastric physiology and the role of gastric dysmotility in dyspepsia and gastroparesis; the stomach in appetite control and obesity; there is an update on the immunology of the stomach and the emerging field of the gastric microbiome. H. pylori-induced gastritis and its associated diseases including peptic ulcers and gastric cancer are addressed together with advances in diagnosis. The conclusions provide a future approach to gastric diseases underpinned by the concept that a healthy stomach is the gateway to a healthy and balanced host. This philosophy should reinforce any public health efforts designed to eradicate major gastric diseases, including stomach cancer.