Mechanisms of postprandial abdominal bloating and distension in functional dyspepsia

Functional Abdominal Bloating and Gut Microbiota: An Update

(1) Background: Functional abdominal bloating and distension (FAB/FAD) are common disorders of the gut-brain interaction. Their physiopathology is complex and not completely clarified, although gut microbiota imbalances play a central role. The treatment of FAB/FAD still represents a clinical challenge for both patients and healthcare providers. Gut microbiota modulation strategies might play a crucial role in their management. The aim of this narrative review was to update the current evidence on FAB/FAD, with a focus on gut microbiota. (2) Methods: In October 2023, a review was conducted through the Medline, PubMed, and Embase databases. Selected literature included all available English-edited studies (randomized controlled trials and cross-sectional, cohort, and case-control studies). (3) Results: Twelve studies were selected, most of which investigated the relationship between IBS and microbiota, with bloating being one of its symptoms. The studies suggest that restoring a balanced microbiome appears to be the most promising solution for better management of FAB/FAD. Targeted approaches, such as the use of probiotics, prebiotics, antibiotics such as rifaximin or dietary modifications, may hold the key to alleviating symptoms. Other therapeutic options, such as diet, neuromodulators, and brain-gut behavioral therapies (i.e., cognitive-behavioral therapy) have shown promising outcomes, but strong data are still lacking. (4) Conclusions: Targeted approaches that focus on the gut microbiota, such as the use of probiotics, prebiotics, and antibiotics, are essential in managing FAB/FAD. Understanding the complex relationship between gut microbiota and FAB/FAD is crucial for developing effective treatments. Further studies are needed to explore the specific roles of different microbial populations in patients with FAB/FAD to enhance therapeutic strategies.

Thoracoabdominal Wall Motion-Guided Biofeedback Treatment of Abdominal Distention: A Randomized Placebo-Controlled Trial

BACKGROUND & AIMS

Abdominal distention results from abdominophrenic dyssynergia (ie, diaphragmatic contraction and abdominal wall relaxation) in patients with disorders of gut-brain interaction. This study aimed to validate a simple biofeedback procedure, guided by abdominothoracic wall motion, for treating abdominal distention.

METHODS

In this randomized, parallel, placebo-controlled trial, 42 consecutive patients (36 women and 6 men; ages 17-64 years) with meal-triggered visible abdominal distention were recruited. Recordings of abdominal and thoracic wall motion were obtained using inductance plethysmography via adaptable belts. The signal was shown to patients in the biofeedback group, who were taught to mobilize the diaphragm. In contrast, the signal was not shown to the patients in the placebo group, who were given a placebo capsule. Three sessions were performed over a 4-week intervention period, with instructions to perform exercises (biofeedback group) or to take placebo 3 times per day (control group) at home. Outcomes were assessed through response to an offending meal (changes in abdominothoracic electromyographic activity and girth) and clinical symptoms measured using daily scales for 7 days.

RESULTS

Patients in the biofeedback group (n = 19) learned to correct abdominophrenic dyssynergia triggered by the offending meal (intercostal activity decreased by a mean ± SE of 82% ± 10%, anterior wall activity increased by a mean ± SE of 97% ± 6%, and increase in girth was a mean ± SE of 108% ± 4% smaller) and experienced improved clinical symptoms (abdominal distention scores decreased by a mean ± SE of 66% ± 5%). These effects were not observed in the placebo group (all, P < .002).

CONCLUSIONS

Abdominothoracic wall movements serve as an effective biofeedback signal for correcting abdominophrenic dyssynergia and abdominal distention in patients with disorders of gut-brain interaction. ClincialTrials.gov, Number: NCT04043208.

Risk Factors and Patient-Reported Outcomes in Chinese Women with Postpartum Diastasis Recti Abdominis: An Observational Study

Purpose

Diastasis recti abdominis (DRA) is a condition in which the linea alba is stretched and widened, and the abdominal muscles are separated from each other. DRA typically occurs in pregnant and postpartum women. We aimed to determine the risk factors and patient-reported outcomes (PROs) of DRA in Chinese postpartum women.

Methods

This observational study was conducted in Hangzhou Hospital of Traditional Chinese Medicine, and involved 534 women who filled out the following risk-factor and PRO questionnaires: SF-MPQ-2, SF-ICIQ, LDQ, EPDS, MBIS, HerQles, and SF-36 (all Chinese versions). The inter-recti distance was measured by palpation. Statistical analyses were performed using SPSS v25.0 software and the Mann-Whitney U-test, chi-square test, binary logistic regression analysis (for risk factors of DRA), and the Kendall and Spearman tests (for correlation analysis).

Results

After childbirth, 78.1% (417/534) of the enrolled women had DRA. Abdominal surgery (P = 0.002), number of pregnancies (P = 0.035), parity (P = 0.012), number of births (P = 0.02), fetal birth weight (P = 0.014), and waist-to-hip ratio in the supine position (P = 0.045) significantly differed between the DRA and non-DRA groups. Caesarean delivery was an independent risk factor for DRA. The PROs were significantly worse in the DRA group than in the non-DRA group.

Conclusion

Caesarean delivery was an independent risk factor for DRA. Women with DRA are more likely to have limited physical activity or function after childbirth, lower self-confidence, and a decreased quality of life.

The Disease Spectrum and Natural History of Patients With Abdominal Bloating or Distension: A Longitudinal Study

Background/Aims

Abdominal bloating or distension (AB/D) is a common complaint in the outpatient of gastroenterology department. Since the potential contributors are numerous and complex, a longitudinal study on the disease spectrum and natural history of patients was performed to better understand the key factors of AB/D.

Methods

Consecutive patients with the chief complaint of AB/D referred to the outpatient clinic were screened. Functional gastrointestinal disorders (FGIDs) were diagnosed according to Rome IV criteria. A 3-year follow-up was performed to seek for the changes in symptoms as well as disease spectrum.

Results

A total of 261 participants were enrolled and 139 completed the follow-up. Most patients suffered from moderate to severe symptoms more than 1 day per week. Common causes of AB/D were FGIDs (51.7%) and organic diseases (17.2%). The latter group was older with lower body mass index (BMI). Functional dyspepsia was the most common type of FGIDs in AB/D. The symptoms of 18.0% of participants failed to improve at the end of the 3-year follow-up, and those diagnosed with FGIDs were most likely to continue to suffer. Abdominal pain was a positive predictive factor for good prognosis in the FGIDs group. Besides, only 22.7% of participants had a consistent diagnosis of FGIDs during follow-up.

Conclusions

FGIDs are the most common diagnosis in patients with AB/D. Symptoms were especially hard to be improved. Classification diagnoses of FGIDs in AB/D patients fluctuated significantly over time.

Clinical Characteristics of Patients Presenting With Bloating as a Predominant Symptom

BACKGROUND

The estimated prevalence of bloating is 15 to 30% in the adult US population and is even higher in patients with disorders of gut-brain interaction (DGBIs). Despite this frequency, there is little research into patients who endorse bloating as a predominant symptom. The aim of this study was to better characterize these patients.

MATERIALS AND METHODS

New patients with DGBIs were asked to identify their 3 most predominant symptoms over the preceding 3 months; those who reported bloating were classified as "bloating predominant." Rome IV and symptom-specific questionnaires were administered to assess for the frequency of DGBIs and other predominant symptoms in this patient population. Using univariable and multivariable modeling, we analyzed the associations between bloating predominance, DGBI subtype, and clinical characteristics.

RESULTS

Of the 586 patients surveyed, 242 (41%) reported predominant bloating. Bloating-predominant patients were more likely to be female, younger, and meet the criteria for IBS-mixed (IBS-M), functional constipation, and functional dyspepsia compared with nonbloating-predominant patients. Bloating-predominant patients were also more likely to endorse concurrently predominant constipation, incomplete evacuation, abdominal pain, belching, and/or nausea. On multivariable logistic regression, constipation and abdominal pain severity were positively associated, although depression was negatively associated with predominant bloating.

CONCLUSIONS

Patients with predominant bloating are more likely to have constipation-related symptoms than diarrhea-related symptoms. They are also more likely to have more severe abdominal pain than patients without predominant bloating. These findings help characterize patients with bloating as a predominant symptom and suggest that diagnosing and treating constipation should be considered as first-line treatment.

Visible abdominal distension in functional gut disorders: Objective evaluation

BACKGROUND

Visible abdominal distension has been attributed to: (A) distorted perception, (B) intestinal gas accumulation, or (C) abdominophrenic dyssynergia (diaphragmatic push and anterior wall relaxation).

METHODS

A pool of consecutive patients with functional gut disorders and visible abdominal distension included in previous studies (n = 139) was analyzed. Patients (61 functional bloating, 74 constipation-predominant irritable bowel syndrome and 4 with alternating bowel habit) were evaluated twice, under basal conditions and during a self-reported episode of visible abdominal distension; static abdominal CT images were taken in 104 patients, and dynamic EMG recordings of the abdominal walls in 76, with diaphragmatic activity valid for analysis in 35.

KEY RESULTS

(A) Objective evidence of abdominal distension was obtained by tape measure (increase in girth in 138 of 139 patients), by CT imaging (increased abdominal perimeter in 96 of 104 patients) and by abdominal EMG (reduced activity, i.e., relaxation, in 73 of 76 patients). (B) Intestinal gas volume was within ±300 ml from the basal value in 99 patients, and above in 5 patients, who nevertheless exhibited a diaphragmatic descent. (C) Diaphragmatic contraction was detected in 34 of 35 patients by EMG (increased activity) and in 82 of 103 patients by CT (diaphragmatic descent).

CONCLUSIONS AND INFERENCES

In most patients complaining of episodes of visible abdominal distention: (A) the subjective claim is substantiated by objective evidence; (B) an increase in intestinal gas does not justify visible abdominal distention; (C) abdominophrenic dyssynergia is consistently evidenced by dynamic EMG recording, but static CT imaging has less sensitivity.

Abdominophrenic Dyssynergia: A Narrative Review

Chronic bloating and abdominal distension are common and highly bothersome gastrointestinal symptoms. Although the differential diagnoses for bloating and distension are broad, these symptoms are frequently associated with disorders of the gut-brain interaction. Functional abdominal bloating may be a result of visceral hypersensitivity, whereas abdominal distension seems to be a somatic behavioral response associated with abdominophrenic dyssynergia, featuring diaphragmatic contraction and abdominal wall relaxation. We review the available literature regarding abdominophrenic dyssynergia and comment on its epidemiology, diagnosis, treatment, and avenues to address in the near future.

Mast cells disrupt the duodenal mucosal integrity: Implications for the mechanisms of barrier dysfunction in functional dyspepsia

BACKGROUND

Functional dyspepsia (FD) is a common functional gastrointestinal (GI) disorder, but its pathophysiology is poorly understood. Mast cells (MCs) may play a critical role in the development of FD. Therefore, the aim of this study was to investigate the effect of MCs on barrier function, tight junction (TJ) proteins and related signaling pathways.

METHODS

The expression of the TJ proteins claudin-8, ZO-1 and occludin in biopsy tissues from seven FD patients and five controls was assessed. Based on the in vivo results, we further investigated the effect of (1) MC degranulation in a coculture model of Caco-2/RBL-2H3 cells and tryptase in Caco-2 monolayers, (2) MC degranulation in the presence or absence of a PAR-2 antagonist and (3) MC degranulation in the presence or absence of an ERK1/2 signaling pathway inhibitor. The epithelial integrity of Caco-2 cell monolayers was assessed by measuring the transepithelial electrical resistance (TEER). The expression of TJ proteins was evaluated by western blotting, QT-PCR and immunostaining.

RESULTS

Epithelial claudin-8, ZO-1 and occludin protein expression were significantly reduced in tissues from FD patients compared with controls. MC degranulation and tryptase decreased the TEER and reduced the expression of TJ proteins in Caco-2 cell monolayers. A PAR-2 antagonist and an ERK1/2 signaling pathway inhibitor significantly reduced the effect of MC degranulation on the TEER and TJ protein expression in Caco-2 cell monolayers.

CONCLUSIONS

MCs disrupt duodenal barrier function by modulating the levels of TJ proteins, and the PAR-2 and ERK1/2 signaling pathways may mediate the pathogenesis of FD.

Effect of Resistant Dextrin on Intestinal Gas Homeostasis and Microbiota

Previous studies have shown that a resistant dextrin soluble fibre has prebiotic properties with related health benefits on blood glucose management and satiety. Our aim was to demonstrate the effects of continuous administration of resistant dextrin on intestinal gas production, digestive sensations, and gut microbiota metabolism and composition. Healthy subjects (n = 20) were given resistant dextrin (14 g/d NUTRIOSE^®, Roquette Frères, Lestrem, France) for four weeks. Outcomes were measured before, at the beginning, end, and two weeks after administration: anal evacuations of gas during daytime; digestive perception, girth, and gas production in response to a standard meal; sensory and digestive responses to a comfort meal; volume of colonic biomass by magnetic resonance; taxonomy and metabolic functions of fecal microbiota by shotgun sequencing; metabolomics in urine. Dextrin administration produced an initial increase in intestinal gas production and gas-related sensations, followed by a subsequent decrease, which magnified after discontinuation. Dextrin enlarged the volume of colonic biomass, inducing changes in microbial metabolism and composition with an increase in short chain fatty acids-producing species and modulation of bile acids and biotin metabolism. These data indicate that consumption of a soluble fibre induces an adaptative response of gut microbiota towards fermentative pathways with lower gas production.

The efficacy of cognitive behavior stress management on functional dyspepsia: A protocol for systematic review and meta-analysis

BACKGROUND

Functional dyspepsia and digestive disorders are common, debilitating and costly. Little information is available about the role of stress management in terms of cognitive-behavioral treatment of dyspepsia. We performed a protocol for systematic review and meta-analysis to evaluate the effectiveness of cognitive behavior stress management for the treatment of functional dyspepsia.

METHODS

A comprehensive search of several databases from 1966 to March 2022 will be conducted. The databases include Ovid Medline In-Process & Other Non-Indexed Citations, Ovid MEDLINE, Ovid EMBASE, Ovid PsycINFO, Ovid Cochrane Central Register of Controlled Trials, Ovid Cochrane Database of Systematic Reviews, and Scopus. The primary outcome for this study was the rate of successful treatment (presence of no more than mild pain or discomfort after treatment). The secondary outcomes were improvement of dyspepsia at short-term (<1 year) and long-term (≥1 year) follow up, improvement in quality of life, and development of treatment-related adverse events. The risk of bias in each included study will be assessed utilizing the Cochrane Collaboration's risk of bias tool. The Review Manager 5.3 (Cochrane Collaboration, Oxford, UK) will be used to analyze the data.

RESULTS

We will synthesize the current studies to evaluate the effectiveness and safety of cognitive behavior stress management on functional dyspepsia.

CONCLUSION

The result of this review will provide more reliable references to help clinicians make decisions when dealing with functional dyspepsia.

Management of bloating

Abdominal bloating is a subjective sensation of trapped abdominal gas, producing abdominal pressure, fullness sensation, and, in some patients, associated objective abdominal distension. In this month's edition of the journal, a new validated questionnaire to assess the prevalence and impact of gas-related symptoms is presented by Duracinsky et al., showing that gas-related abdominal symptoms are prevalent in patients with irritable bowel syndrome and have a measurable impact on patients daily life. A parallel study by Gardiner et al. assessing the severity of bloating in functional gastrointestinal disorders shows that severe bloating is associated with the severity of abdominal pain, constipation, and somatization, advancing our understanding of the clinical characteristics and relevance of gas-related symptoms in the broad spectrum of functional gastrointestinal disorders. Management of bloating includes non-pharmacological and pharmacological strategies. Dietary interventions to reduce intestinal fermentation and ingestion of food supplements like prebiotics or probiotics can reduce bloating by reducing gas production. The main targets of pharmacological treatments are to improve transit and evacuation with prokinetics, to improve intestinal gas tolerance with antispasmodics and/or neuromodulators, and to modify intestinal microbiota with antibiotics. Secretagogues act by increasing intestinal secretion and decreasing visceral sensitivity and have been reported to be an effective treatment alternative for patients with bloating associated with constipation. Biofeedback therapy addressed to correct abdomino-phrenic dysynergia may be useful for patients with objective abdominal distension, and patients with bloating associated with outlet obstructed defecation may benefit from anorectal biofeedback.

A Fermented Milk Product Containing B. lactis CNCM I-2494 Improves the Tolerance of a Plant-Based Diet in Patients with Disorders of Gut-Brain Interactions

Healthy, plant-based diets, rich in fermentable residues, may induce gas-related symptoms. The aim of this exploratory study was to assess the effects of a fermented milk product, containing probiotics, on the tolerance of a healthy diet in patients with disorders of gut–brain interactions (DGBI), complaining of excessive flatulence. In an open design, a 3-day healthy, mostly plant-based diet was administered to patients with DGBI (52 included, 43 completed) before and at the end of 28 days of consumption of a fermented milk product (FMP) containing Bifidobacterium animalis subsp. lactis CNCM I-2494 and lactic acid bacteria. As compared to a habitual diet, the flatulogenic diet increased the perception of digestive symptoms (flatulence score 7.1 ± 1.6 vs. 5.8 ± 1.9; p < 0.05) and the daily number of anal gas evacuations (22.4 ± 12.5 vs. 16.5 ± 10.2; p < 0.0001). FMP consumption reduced the flatulence sensation score (by –1.6 ± 2.2; p < 0.05) and the daily number of anal gas evacuations (by –5.3 ± 8.2; p < 0.0001). FMP consumption did not significantly alter the overall gut microbiota composition, but some changes in the microbiota correlated with the observed clinical improvement. The consumption of a product containing B. lactis CNCM I-2494 improved the tolerance of a healthy diet in patients with DGBI, and this effect may be mediated, in part, by the metabolic activity of the microbiota.

Differential Effects of Western and Mediterranean-Type Diets on Gut Microbiota: A Metagenomics and Metabolomics Approach

Our aim was to determine the effect of diet on gut microbiota, digestive function and sensations, using an integrated clinical, metagenomics and metabolomics approach. We conducted a cross-over, randomised study on the effects of a Western-type diet versus a fibre-enriched Mediterranean diet. In 20 healthy men, each diet was administered for 2 weeks preceded by a 2-week washout diet. The following outcomes were recorded: (a) number of anal gas evacuations; (b) digestive sensations; (c) volume of gas evacuated after a probe meal; (d) colonic content by magnetic resonance imaging; (e) gut microbiota taxonomy and metabolic functions by shotgun sequencing of faecal samples; (f) urinary metabolites using untargeted metabolomics. As compared to a Western diet, the Mediterranean diet was associated with (i) higher number of anal gas evacuations, (ii) sensation of flatulence and borborygmi, (iii) larger volume of gas after the meal and (iv) larger colonic content. Despite the relatively little difference in microbiota composition between both diets, microbial metabolism differed substantially, as shown by urinary metabolite profiles and the abundance of microbial metabolic pathways. The effects of the diet were less evident in individuals with robust microbiotas (higher beta-diversity). To conclude, healthy individuals tolerate dietary changes with minor microbial modifications at the composition level but with remarkable variation in microbial metabolism.

Gastrointestinal Contributions to the Postprandial Experience

Food ingestion induces homeostatic sensations (satiety, fullness) with a hedonic dimension (satisfaction, changes in mood) that characterize the postprandial experience. Both types of sensation are secondary to intraluminal stimuli produced by the food itself, as well as to the activity of the digestive tract. Postprandial sensations also depend on the nutrient composition of the meal and on colonic fermentation of non-absorbed residues. Gastrointestinal function and the sensitivity of the digestive tract, i.e., perception of gut stimuli, are determined by inherent individual factors, e.g., sex, and can be modulated by different conditioning mechanisms. This narrative review examines the factors that determine perception of digestive stimuli and the postprandial experience.

Abdominothoracic Postural Tone Influences the Sensations Induced by Meal Ingestion

Postprandial objective abdominal distention is frequently associated with a subjective sensation of abdominal bloating, but the relation between both complaints is unknown. While the bloating sensation has a visceral origin, abdominal distention is a behavioral somatic response, involving contraction and descent of the diaphragm with protrusion of the anterior abdominal wall. Our aim was to determine whether abdominal distention influences digestive sensations. In 16 healthy women we investigated the effect of intentional abdominal distention on experimentally induced bloating sensation (by a meal overload). Participants were first taught to produce diaphragmatic contraction and visible abdominal distention. After a meal overload, sensations of bloating (0 to 10) and digestive well-being (-5 to + 5) were measured during 30-s. maneuvers alternating diaphragmatic contraction and diaphragmatic relaxation. Compared to diaphragmatic relaxation, diaphragmatic contraction was associated with diaphragmatic descent (by 21 + 3 mm; p < 0.001), objective abdominal distension (32 + 5 mm girth increase; p = 0.001), more intense sensation of bloating (7.3 + 0.4 vs. 8.0 + 0.4 score; p = 0.010) and lower digestive well-being (-0.9 + 0.5 vs. -1.9 + 0.5 score; p = 0.028). These results indicate that somatic postural tone underlying abdominal distention worsens the perception of visceral sensations (ClinicalTrials.gov ID: NCT04691882).

Management of Chronic Abdominal Distension and Bloating

Abdominal bloating and distension are 2 of the most commonly reported gastrointestinal symptoms. Abdominal bloating is characterized by symptoms of trapped gas, abdominal pressure, and fullness. Abdominal distension is defined as a measurable increase in abdominal girth. These symptoms frequently co-exist, although they can occur separately. Defined by Rome IV criteria, functional abdominal bloating and distension commonly coincide with other functional gastrointestinal disorders, such as functional dyspepsia, irritable bowel syndrome, and functional constipation. Abdominal bloating and distension can develop for multiple reasons, including food intolerances, a previous infection that perturbed the intestinal microbiota, disordered visceral sensation, delayed intestinal transit, or an abnormal viscero-somatic reflux. Treatment can be challenging to patients and providers-no regimen has been consistently successful. Successful treatment involves identifying the etiology, assessing severity, educating and reassuring patients, and setting expectations. Therapeutic options include dietary changes, probiotics, antibiotics, prokinetic agents, antispasmodics, neuromodulators, and biofeedback. We review the epidemiology and effects of chronic bloating and distension and pathophysiology, discuss appropriate diagnostic strategies, and assess available treatment options.

Sex Differences and Commonalities in the Impact of a Palatable Meal on Thalamic and Insular Connectivity

The neural mechanisms underlying subjective responses to meal ingestion remain incompletely understood. We previously showed in healthy men an increase in thalamocortical, and a decrease in insular-cortical connectivity in response to a palatable meal. As sex is increasingly recognized as an important biological variable, we aimed to evaluate sex differences and commonalities in the impact of a well-liked meal on thalamic and anterior insular connectivity in healthy individuals. Participants (20 women and 20 age-matched men) underwent resting-state magnetic resonance imaging (rsMRI) before and after ingesting a palatable meal. In general, the insula showed extensive postprandial reductions in connectivity with sensorimotor and prefrontal cortices, while the thalamus showed increases in connectivity with insular, frontal, and occipital cortices, in both women and men. However, reductions in insular connectivity were more prominent in men, and were related to changes in meal-related sensations (satiety and digestive well-being) in men only. In contrast, increases in thalamic connectivity were more prominent in women, and were related to changes in satiety and digestive well-being in women only. These results suggest that brain imaging may provide objective and sex-specific biomarkers of the subjective feelings associated with meal ingestion.

Gut Microbiota Dysbiosis in Functional Dyspepsia

Functional dyspepsia (FD) is one of the most prevalent chronic functional gastrointestinal disorders. Several distinct pathophysiological mechanisms, including gastro duodenal motor disorders, visceral hypersensitivity, brain-gut interactions, duodenal subtle inflammation, and genetic susceptibility, have been implicated in the pathogenesis of the disease, so far. However, emerging evidence suggests that both quantitative and qualitative disturbances of the gastrointestinal microbiota may also be implicated. In this context, several studies have demonstrated differences of the commensal bacterial community between patients with FD and healthy controls, while others have shown that intestinal dysbiosis might associate with disease’s symptoms severity. Elucidating these complex interactions constituting the microbiota and host crosstalk, may eventually lead to the discovery of novel, targeted therapeutic approaches that may be efficacious in treating the multiple aspects of the disorder. In this review, we summarize the data of the latest research with focus on the association between gut microbiota alterations and host regarding the pathogenesis of FD.

Food, Eating, and the Gastrointestinal Tract

Food ingestion induces a metered response of the digestive system. Initially, the upper digestive system reacts to process and extract meal substrates. Later, meal residues not absorbed in the small bowel, pass into the colon and activate the metabolism of resident microbiota. Food consumption also induces sensations that arise before ingestion (e.g., anticipatory reward), during ingestion (e.g., gustation), and most importantly, after the meal (i.e., the postprandial experience). The postprandial experience involves homeostatic sensations (satiety, fullness) with a hedonic dimension (digestive well-being, mood). The factors that determine the postprandial experience are poorly understood, despite their potential role in personalized diets and healthy eating habits. Current data suggest that the characteristics of the meal (amount, palatability, composition), the activity of the digestive system (suited processing), and the receptivity of the eater (influenced by multiple conditioning factors) may be important in this context.

A Fermented Milk Product with B. Lactis CNCM I-2494 and Lactic Acid Bacteria Improves Gastrointestinal Comfort in Response to a Challenge Diet Rich in Fermentable Residues in Healthy Subjects

Background: Healthy plant-based diets rich in fermentable residues may induce gas-related symptoms. Our aim was to determine the potential of a fermented milk product with probiotics in improving digestive comfort with such diets. Methods: In an open design, a 3-day high-residue diet was administered to healthy subjects (n = 74 included, n = 63 completed) before and following 28 days consumption of a fermented milk product (FMP) containing Bifidobacterium animalis subsp. lactis CNCM I-2494 and lactic acid bacteria. Main outcomes: digestive sensations, number of daytime anal gas evacuations, and gas volume evacuated during 4 h after a probe meal. Results: As compared to the habitual diet, the high-residue diet induced gas-related symptoms (flatulence score 4.9 vs. 1.2; p ≤ 0.0001), increased the daily number of anal gas evacuations (20.7 vs. 8.7; p < 0.0001), and impaired digestive well-being (1.0 vs. 3.4; p < 0.05). FMP consumption reduced flatulence sensation (by −1.7 [−1.9; −1.6]; p < 0.0001), reduced the number of daily evacuations (by −5.8 [−6.5; −5.1]; p < 0.0001), and improved digestive well-being (by +0.6 [+0.4; +0.7]; p < 0.05). FMP consumption did not affect the gas volume evacuated after a probe meal. Conclusion: In healthy subjects, consumption of a FMP containing B. lactis CNCM I-2494 and lactic acid bacteria improves the tolerance of a flatulogenic diet by subjective and objective criteria (sensations and number of anal gas evacuations, respectively).

Abdominal distension after eating lettuce: The role of intestinal gas evaluated in vitro and by abdominal CT imaging

BACKGROUND

Some patients complain that eating lettuce, gives them gas and abdominal distention. Our aim was to determine to what extent the patients' assertion is sustained by evidence.

METHODS

An in vitro study measured the amount of gas produced during the process of fermentation by a preparation of human colonic microbiota (n = 3) of predigested lettuce, as compared to beans, a high gas-releasing substrate, to meat, a low gas-releasing substrate, and to a nutrient-free negative control. A clinical study in patients complaining of abdominal distention after eating lettuce (n = 12) measured the amount of intestinal gas and the morphometric configuration of the abdominal cavity in abdominal CT scans during an episode of lettuce-induced distension as compared to basal conditions.

KEY RESULTS

Gas production by microbiota fermentation of lettuce in vitro was similar to that of meat (P = .44), lower than that of beans (by 78 ± 15%; P < .001) and higher than with the nutrient-free control (by 25 ± 19%; P = .05). Patients complaining of abdominal distension after eating lettuce exhibited an increase in girth (35 ± 3 mm larger than basal; P < .001) without significant increase in colonic gas content (39 ± 4 mL increase; P = .071); abdominal distension was related to a descent of the diaphragm (by 7 ± 3 mm; P = .027) with redistribution of normal abdominal contents.

CONCLUSION AND INFERENCES

Lettuce is a low gas-releasing substrate for microbiota fermentation and lettuce-induced abdominal distension is produced by an uncoordinated activity of the abdominal walls. Correction of the somatic response might be more effective than the current dietary restriction strategy.

Intestinal gases: influence on gut disorders and the role of dietary manipulations

The inner workings of the intestines, in which the body and microbiome intersect to influence gut function and systemic health, remain elusive. Carbon dioxide, hydrogen, methane and hydrogen sulfide, as well as a variety of trace gases, are generated by the chemical interactions and microbiota within the gut. Profiling of these intestinal gases and their responses to dietary changes can reveal the products and functions of the gut microbiota and their influence on human health. Indeed, different tools for measuring these intestinal gases have been developed, including newly developed gas-sensing capsule technology. Gases can, according to their type, concentration and volume, induce or relieve abdominal symptoms, and might also have physiological, pathogenic and therapeutic effects. Thus, profiling and modulating intestinal gases could be powerful tools for disease prevention and/or therapy. As the interactions between the microbiota, chemical constituents and fermentative substrates of the gut are principally influenced by dietary intake, altering the diet, which, in turn, changes gas profiles, is the main therapeutic approach for gastrointestinal disorders. An improved understanding of the complex interactions within the intestines that generate gases will enhance our ability to prevent, diagnose, treat and monitor many gastrointestinal disorders.

Efficacy of Jianpi Liqi therapy for functional dyspepsia: A meta-analysis of randomized, positive medicine-controlled trials

BACKGROUND

We performed this meta-analysis to assess the efficacy and safety of Jianpi Liqi therapy (JLT), a traditional Chinese medicine therapy, in treating functional dyspepsia (FD).

METHODS

We systematically searched 13 databases from their inception to 15th, May 2019. Eligible studies were randomized controlled trials (RCTs) that compared JLT medicine with conventional pharmacotherapy (CP) in treating patients with FD. Cochrane Collaboration tool, Review Manager 5.3 and STATA 11.0, GRADE profiler 3.6 were used for evaluating risk of bias, analyzing, and assessing quality of evidence respectively.

RESULTS

After exclusions, 15 RCTs including a total of 1451 participants were included for analysis. We found evidence that JLT had better efficacy than CP (domperidone, omeprazole, esomeprazole, mosapride, lansoprazole, compound digestive enzymes, lactasin tablets) for FD (OR 0.34; 95% CI 0.26, 0.45; P < .00001). Moreover, JLT had more improvement on symptoms including abdominal pain, abdominal distention, early satiety, belching, poor appetite, and fatigue compared with CP. In addition, serious adverse events were not observed in treatment courses.

CONCLUSION

This meta-analysis suggested that JLT appears to have better efficacy in treating FD compared with CP. It may be an effective and safe therapy option for patients with FD. Though, more large-sample and strictly designed RCTs are needed to confirm our findings.PROSPERO registration number: CRD42019133241.

Ameliorating effects of optimized gastric electrical stimulation and mechanisms involving nerve growth factor and opioids in a rodent model of gastric hypersensitivity

BACKGROUND

Gastric electrical stimulation (GES) has been applied to treat gastric motility disorders for decades. This study was designed to investigate the effects and mechanisms of GES for visceral hypersensitivity in a rodent model of functional dyspepsia (FD).

METHODS

Male Sprague-Dawley rat pups at 10-days old received 0.1% iodoacetamide (IA) daily for 6 days. The experiments were performed when the rats reached 8-11 weeks of age, and visceral hypersensitivity was established. Then, GES parameters were optimized and the chronic effects of GES on gastric hypersensitivity were assessed by electromyogram (EMG). Naloxone (3 mg/kg), D-Phe-Cys-Tyr-D-Trp-Orn-Thr-Pen-Thr-NH2 (CTOP, 1 mg/kg), and anti-NGF (16 μg/kg) were individually intraperitoneally injected to investigate opioid and nerve growth factor (NGF) mechanisms. Tissues were analyzed for NGF expression.

KEY RESULTS

In the IA-treated rats, the visceromotor response to gastric distension was significantly increased, and both acute GES with optimized stimulation parameters (0.25 seconds on, 0.25 seconds off, 100 Hz, 0.25 ms, 6 mA) and chronic GES (7 days, 2 hours/day) normalized gastric hypersensitivity. The inhibitory effect of GES on gastric hypersensitivity was blocked by naloxone and CTOP. Anti-NGF normalized EMG responses in IA-treated rats. The expressions of NGF in the tissues of IA-treated rats were dramatically increased, and these increases were suppressed with GES.

CONCLUSIONS AND INFERENCES

GES with optimized parameters improves gastric hypersensitivity induced by neonatal treatment of IA mediated peripherally by suppressing NGF and via the opioid mechanism involving the µ receptor. GES as a potential therapy for treating visceral pain may be explored in clinical studies.

Transcutaneous electrical acustimulation synchronized with inspiration improves gastric accommodation impaired by cold stress in healthy subjects

BACKGROUND

The aim of this study was to investigate whether transcutaneous electrical acustimulation (TEA) synchronized with inspiration (STEA), a method known to enhance vagal activity, was more effective than TEA in improving cold stress-induced impairment in gastric accommodation (GA) and dyspeptic symptoms in healthy subjects.

METHODS

Each of fifteen healthy subjects was studied in five randomized sessions: control (warm nutrient liquid), cold nutrient liquid (CNL), CNL+sham-TEA, CNL+TEA, and CNL+STEA. The subjects were requested to drink Ensure until reaching maximum satiety. STEA was performed using the same parameters as TEA but asking the subjects to breathe in when they sensed each stimulation train. The electrogastrogram (EGG) and electrocardiogram (ECG) were recorded to assess gastric slow waves (GSW) and autonomic functions, respectively.

KEY RESULTS

GA was reduced with the CNL in comparison with the warm drink but increased with TEA and STEA; STEA was more potent than TEA in improving GA; STEA was more potent in improving GSW than TEA; STEA significantly increased vagal activity and decreased sympathetic activity compared with TEA.

CONCLUSIONS AND INFERENCES

TEA synchronized with inspiration is more potent than TEA in improving cold stress-induced impairment in GA and GSW and dyspeptic symptoms and might be a novel noninvasive therapy for treating stress-induced dysmotility and dyspeptic symptoms.

The Gut Microbiome in Adult and Pediatric Functional Gastrointestinal Disorders

The importance of gut microbiota in gastrointestinal (GI) physiology was well described, but our ability to study gut microbial ecosystems in their entirety was limited by culture-based methods prior to the sequencing revolution. The advent of high-throughput sequencing opened new avenues, allowing us to study gut microbial communities as an aggregate, independent of our ability to culture individual microbes. Early studies focused on association of changes in gut microbiota with different disease states, which was necessary to identify a potential role for microbes and generate novel hypotheses. Over the past few years the field has moved beyond associations to better understand the mechanistic implications of the microbiome in the pathophysiology of complex diseases. This movement also has resulted in a shift in our focus toward therapeutic strategies, which rely on better understanding the mediators of gut microbiota-host cross-talk. It is not surprising the gut microbiome has been implicated in the pathogenesis of functional gastrointestinal disorders given its role in modulating physiological processes such as immune development, GI motility and secretion, epithelial barrier integrity, and brain-gut communication. In this review, we focus on the current state of knowledge and future directions in microbiome research as it pertains to functional gastrointestinal disorders. We summarize the factors that help shape the gut microbiome in human beings. We discuss data from animal models and human studies to highlight existing paradigms regarding the mechanisms underlying microbiota-mediated alterations in physiological processes and their relevance in human interventions. While translation of microbiome science is still in its infancy, the outlook is optimistic and we are advancing in the right direction toward precise mechanism-based microbiota therapies.

Abdominal distension in health and irritable bowel syndrome: The effect of bladder filling

BACKGROUND & AIMS

Abdominal distension is a common feature of irritable bowel syndrome (IBS), which is difficult to treat and can have the appearance of late pregnancy. It results from an abnormality of the normal accommodation reflex which keeps abdominal girth constant despite changes in gastrointestinal volume resulting from food ingestion or gas accumulation. We speculated that bladder filling might also trigger this abnormal reflex in IBS and this study tested this hypothesis.

METHODS

Eight females with IBS (aged 21-43, mean 34) were compared with seven female controls (aged 19-56, mean 31) at the same time in the menstrual cycle. Abdominal girth in response to maximum tolerated bladder filling following ingestion of 1500 mls of water was measured using abdominal inductance plethysmography. Symptoms, girth change after bladder emptying, and urine volumes were also recorded.

KEY RESULTS

Baseline girth of patients and controls was 84.8 and 79.9 cm respectively. After reaching maximum tolerated bladder filling, girth increased by a mean of 6.4 (Standard deviation (SD) 2.1) cm in patients compared with 3.5 (1.1) in controls (P = 0.006), with patients having symptoms of bladder hypersensitivity. After voiding urine, girth reduced by 5.3 (3.1) and 1.9 (1.2) in patients vs controls (P = 0.018), despite passing similar mean urine volumes, 789 (364) mls vs 671(286) (P = 0.50).

CONCLUSIONS & INFERENCES

Bladder filling contributes to abdominal distension in IBS and is unrelated to urine volume suggesting that bladder stretch or hypersensitivity might trigger this response. Frequent bladder emptying may help control this intrusive problem which is very challenging to manage.

Characterization of Simultaneous Pressure Waves as Biomarkers for Colonic Motility Assessed by High-Resolution Colonic Manometry

Simultaneous pressure waves (SPWs) in manometry recordings of the human colon have been associated with gas expulsion. Our hypothesis was that the SPW might be a critical component of most colonic motor functions, and hence might act as a biomarker for healthy colon motility. To that end, we performed high-resolution colonic manometry (HRCM), for the first time using an 84-sensor (1 cm spaced) water-perfused catheter, in 17 healthy volunteers. Intraluminal pressure patterns were recorded during baseline, proximal and rectal balloon distention, after a meal and following proximal and rectal luminal bisacodyl administration. Quantification was performed using software, based on Image J, developed during this study. Gas expulsion was always associated with SPWs, furthermore, SPWs were associated with water or balloon expulsion. SPWs were prominently emerging at the termination of proximal high amplitude propagating pressure waves (HAPWs); we termed this motor pattern HAPW-SPWs; hence, SPWs were often not a pan-colonic event. SPWs and HAPW-SPWs were observed at baseline with SPW amplitudes of 12.0 ± 8.5 mmHg and 20.2 ± 7.2 mmHg respectively. The SPW occurrence and amplitude significantly increased in response to meal, balloon distention and luminal bisacodyl, associated with 50.3% anal sphincter relaxation at baseline, which significantly increased to 59.0% after a meal, and 69.1% after bisacodyl. Often, full relaxation was achieved. The SPWs associated with gas expulsion had a significantly higher amplitude compared to SPWs without gas expulsion. SPWs could be seen to consist of clusters of high frequency pressure waves, likely associated with a cluster of fast propagating, circular muscle contractions. SPWs were occasionally observed in a highly rhythmic pattern at 1.8 ± 1.2 cycles/min. Unlike HAPWs, the SPWs did not obliterate haustral boundaries thereby explaining how gas can be expelled while solid content can remain restrained by the haustral boundaries. In conclusion, the SPW may become a biomarker for normal gas transit, the gastrocolonic reflex and extrinsic neural reflexes. The SPW assessment reveals coordination of activities in the colon, rectum and anal sphincters. SPWs may become of diagnostic value in patients with colonic dysmotility.

Symptomatology Correlations Between the Diaphragm and Irritable Bowel Syndrome

Irritable bowel syndrome (IBS) is one of the most debilitating and common gastrointestinal disorders; nevertheless, its pathophysiology is still unclear. It affects 11% of the world's population, and is characterized by alternating periods of pain and/or motility disorders with periods of remission and without any evidence of any structural and functional organic variation. It has been recently proposed that an altered contractile ability of the diaphragm muscle might adversely influence intestinal motility. The text reviews the diaphragm's functions, anatomy, and neurological links in correlation with the presence of chronic symptoms associated to IBS, like chronic low back pain, chronic pelvic pain, chronic headache, and temporomandibular joint dysfunction, vagus nerve inflammation, and depression and anxiety. The interplay between an individual's breath dynamic and intestinal behaviour is still an unaddressed point in the physiopathology of IBS, and the paucity of scientific studies should recommend further research to better understand the importance of breathing in this syndrome.

Biogastronomy: Factors that determine the biological response to meal ingestion

BACKGROUND

The biological response to a meal includes physiological changes, primarily related to the digestive process, and a sensory experience, involving sensations related to the homeostatic control of food consumption, eg, satiety and fullness, with a hedonic dimension, ie associated with changes in digestive well-being and mood. The responses to a meal include a series of events before, during and after ingestion. While much attention has been paid to the events before and during ingestion, relatively little is known about the postprandial sensations, which are key to the gastronomical experience.

PURPOSE

The aim of this narrative review is to provide a comprehensive overview and to define the framework to investigate the factors that determine the postprandial experience. Based on a series of proof-of-concept studies and related information, we propose that the biological responses to a meal depend on the characteristics of the meal, primarily its palatability and composition, and the responsiveness of the guest, which may be influenced by multiple previous and concurrent conditioning factors. This information provides the scientific backbone to the development of personalized gastronomy.

[Bloating]

Bloating is one of the most common and troublesome problems in a large proportion of patients with gastrointestinal disorders but the mechanism is not completely understood. Several factors, including gas-producing intestinal microbiota, disturbed handling of intestinal gas, visceral hypersensitivity, abnormal viscero-somatic responses, fermentable diet, and psychological factors, have been suggested as mechanisms. For an assessment, thorough medical history-taking and physical examination are the first steps. On the other hand, organic disorders should always be considered first for a differential diagnosis. The therapeutic options available are considered challenging and still limited in clinical practice. The treatment strategy may include diet modification, pharmacologic approach, psychiatric approach, biofeedback, etc. Further studies will be needed to explore the variable mechanism of bloating and develop an efficient treatment.

Correction of Abdominal Distention by Biofeedback-Guided Control of Abdominothoracic Muscular Activity in a Randomized, Placebo-Controlled Trial

BACKGROUND & AIMS

Abdominal distention is produced by abnormal somatic postural tone. We developed an original biofeedback technique based on electromyography-guided control of abdominothoracic muscular activity. We performed a randomized, placebo-controlled study to demonstrate the superiority of biofeedback to placebo for the treatment of abdominal distention.

METHODS

At a referral center in Spain, we enrolled consecutive patients with visible abdominal distention who fulfilled the Rome III criteria for functional intestinal disorders (47 women, 1 man; 21-74 years old); 2 patients assigned to the placebo group withdrew and 2 patients assigned to biofeedback were not valid for analysis. Abdominothoracic muscle activity was recorded by electromyography. The patients in the biofeedback group were shown the signal and instructed to control muscle activity, whereas patients in the placebo received no instructions and were given oral simethicone. Each patient underwent 3 sessions over a 10-day period. The primary outcomes were subjective sensation of abdominal distention, measured by graphic rating scales for 10 consecutive days before and after the intervention.

RESULTS

Patients in the biofeedback group effectively learned to reduce intercostal activity (by a mean 45% ± 3%), but not patients in the placebo group (reduced by a mean 5% ± 2%; P < .001). Patients in the biofeedback group learned to increase anterior wall muscle activity (by a mean 101% ± 10%), but not in the placebo group (decreased by a mean 4% ± 2%; P < .001). Biofeedback resulted in a 56% ± 1% reduction of abdominal distention (from a mean score of 4.6 ± 0.2 to 2.0 ± 0.2), whereas patients in the placebo group had a reduction of only 13% ± 8% (from a mean score of 4.7 ± 0.1 to 4.1 ± 0.4) (P < .001).

CONCLUSIONS

In a randomized trial of patients with a functional intestinal disorder, we found that abdominal distention can be effectively corrected by biofeedback-guided control of abdominothoracic muscular activity, compared with placebo. ClincialTrials.gov no: NCT01205100.

Functional dyspepsia

Functional dyspepsia is one of the most prevalent functional gastrointestinal disorders. Functional dyspepsia comprises three subtypes with presumed different pathophysiology and aetiology: postprandial distress syndrome (PDS), epigastric pain syndrome (EPS) and a subtype with overlapping PDS and EPS features. Functional dyspepsia symptoms can be caused by disturbed gastric motility (for example, inadequate fundic accommodation or delayed gastric emptying), gastric sensation (for example, sensations associated with hypersensitivity to gas and bloating) or gastric and duodenal inflammation. A genetic predisposition is probable but less evident than in other functional gastrointestinal disorders, such as irritable bowel syndrome (IBS). Psychiatric comorbidity and psychopathological state and trait characteristics could also play a part, although they are not specific to functional dyspepsia and are less pronounced than in IBS. Possible differential diagnoses include Helicobacter pylori infection and peptic ulceration. Pharmacological therapy is mostly based on the subtype of functional dyspepsia, such as prokinetic and fundus-relaxing drugs for PDS and acid-suppressive drugs for EPS, whereas centrally active neuromodulators and herbal drugs play a minor part. Psychotherapy is effective only in a small subset of patients, whereas quality of life can be severely affected in nearly all patients. Future therapies might include novel compounds that attempt to treat the underlying gastric and duodenal inflammation.

Colonic gas homeostasis: Mechanisms of adaptation following HOST-G904 galactooligosaccharide use in humans

BACKGROUND

We have shown that a galactooligosaccharide prebiotic administration (HOST-G904) initially increased intestinal gas production and this increase declined back to baseline after 2 week administration. Our aim was to determine the mechanism of microbiota adaptation; i.e., to determine whether the net reduction is due to decreased overall production or increased gas consumption.

METHODS

In 10 healthy subjects, intestinal gas production and intraluminal disposal was measured before, at the beginning and after 2 week of HOST-G904 prebiotic administration. Anal gas was collected for 4 hour after a probe meal. Paired studies were performed without and with high-rate infusion of exogenous gas (24 mL/min) into the jejunum to wash-out the endogenous gas produced by bacterial fermentation. The exogenous gas infused was labeled (5% SF₆ ) to calculate the proportion of endogenous gas evacuated.

KEY RESULTS

The volume of intestinal gas produced i.e., endogenous gas washed-out, increased by 37% at the beginning of HOST-G904 administration (P=.049 vs preadministration) and decreased down to preadministration level after 2 week administration (P=.030 vs early administration). The proportion of gas eliminated from the lumen before reaching the anus tended to increase after 2-week administration (87±3% vs 78±5% preadministration; P=.098).

CONCLUSIONS & INFERENCES

Adaptation to regular consumption of HOST-G904 prebiotic involves a shift in microbiota metabolism toward low-gas producing pathways, with a non-significant increase in gas-consuming activity. Hence, regular consumption of HOST-G904 regulates intestinal gas metabolism: less gas is produced and a somewhat larger proportion of it is consumed.

Efficacy and safety of Xiangsha Liujunzi granules for functional dyspepsia: A multi-center randomized double-blind placebo-controlled clinical study

AIM

To assess the efficacy and safety of a Chinese herbal medicine (CHM), Xiangsha Liujunzi granules, in the treatment of patients with functional dyspepsia (FD).

METHODS

We performed a randomized, double-blind, placebo-controlled trial with patients from three centers. Two hundred and sixteen subjects diagnosed with FD according to ROME III criteria and confirmed by upper gastrointestinal endoscopy and spleen-deficiency and Qi-stagnation syndrome were selected to receive Xiangsha Liujunzi granules or placebo for 4 wk in a 2:1 ratio by blocked randomization. The subjects also received follow-up after the 4-wk intervention. Herbal or placebo granules were dissolved in 300 mL of water. Participants in both groups were administered 130 mL (45 °C) three times a day. Participants were evaluated prior to and following 4 wk of the intervention in terms of changes in the postprandial discomfort severity scale (PDSS) score, clinical global impression (CGI) scale score, hospital anxiety and depression scale (HADS) score, traditional Chinese medicine symptoms score (SS), scores of various domains of the 36-item short form health survey (SF-36), gastric emptying (GE) and any observed adverse effects.

RESULTS

Compared with the placebo group, patients in the CHM group showed significant improvements in the scores of PDSS, HADS, SS, SF-36 and CGI scale (P < 0.05 or P < 0.01). They also showed the amelioration in the GE rates of the proximal stomach and distal stomach (P < 0.05 or P < 0.01).

CONCLUSION

Xiangsha Liujunzi granules offered significant symptomatic improvement in patients with FD.

Bloating and Abdominal Distension: Old Misconceptions and Current Knowledge

Bloating, as a symptom and abdominal distension, as a sign, are both common functional-type complaints and challenging to manage effectively. Individual patients may weight differently the impact of bloating and distension on their well-being. Complaints may range from chronic highly distressing pain to simply annoying and unfashionable protrusion of the abdomen. To avoid mishaps, organic bloating, and distension should always be considered first and appropriated assessed. Functional bloating and distension often present in association with other manifestations of irritable bowel syndrome or functional dyspepsia and in that context patients tend to regard them as most troublesome. A mechanism-based management bloating and distension should be ideal but elucidating key operational mechanisms in individual patients is not always feasible. Some clues may be gathered through a detailed dietary history, by assessing bowel movement frequency and stool consistency and special imaging technique to measure abdominal shape during episodes of distension. In severe, protracted cases it may be appropriate to refer the patient to a specialized center where motility, visceral sensitivity, and abdominal muscle activity in response to intraluminal stimuli may be measured. Therapeutic resources focussed upon presumed or demonstrated pathogenetic mechanism include dietary modification, microbiome modulation, promoting gas evacuation, attenuating visceral perception, and controlling abdominal wall muscle activity via biofeedback.

Brain networks associated with cognitive and hedonic responses to a meal

BACKGROUND

We recently reported interrelated digestive, cognitive, and hedonic responses to a meal. The aim of this study was to identify brain networks related to the hedonic response to eating.

METHODS

Thirty-eight healthy subjects (20-38 age range) were evaluated after a 5-hour fast and after ingestion of a test meal (juice and warm ham and cheese sandwich, 300 mL, 425 kcal). Perceptual and affective responses (satiety, abdominal fullness, digestive well-being, and positive mood), and resting scans of the brain using functional MRI (3T Trio, Siemens, Germany) were evaluated immediately before and after the test meal. A high-order group independent component analysis was performed to investigate ingestion-related changes in the intrinsic connectivity of brain networks, with a focus on thalamic and insular networks.

KEY RESULTS

Ingestion induced satiation (3.3±0.4 score increase; P<.001) and abdominal fullness (2.4±0.3 score increase; P<.001). These sensations included an affective dimension involving digestive well-being (2.8±0.3 score increase; P<.001) and positive mood (1.8±0.2 score increase; P<.001). In general, thalamo-cortical connectivity increased with meal ingestion while insular-cortical connectivity mainly decreased. Furthermore, larger meal-induced changes (increase/decrease) in specific thalamic connections were associated with smaller changes in satiety/fullness. In contrast, a larger meal-induced decrease in insular-anterior cingulate cortex connectivity was associated with increased satiety, fullness, and digestive well-being.

CONCLUSIONS AND INFERENCES

Perceptual and emotional responses to food intake are related to brain connectivity in defined functional networks. Brain imaging may provide objective biomarkers of subjective effects of meal ingestion.

Relation between cognitive and hedonic responses to a meal

BACKGROUND

Ingestion of a meal induces cognitive and hedonic sensations and our aim was to determine the relation between both dimensions.

METHODS

In three groups of healthy non-obese men (n=10 per group) three types of meals with equivalent levels of palatability were tested: a liquid meal, a solid-liquid low-calorie meal, and a solid-liquid high-calorie meal. The cognitive and hedonic responses were measured on 10-cm scales before and during the 30-minute postprandial period.

KEY RESULTS

The liquid meal induced a relatively strong cognitive response with satiation (4.7±0.7 score increment), fullness (3.3±0.7 score increment), and inhibition of desire of eating a food of choice; in contrast, its impact on sensation of digestive well-being and satisfaction was not significant (0.7±0.7 score increment). The high-calorie solid-liquid meal, with larger volume load and caloric content, induced much lower satiation (2.4±0.8 score increment; P=.041 vs liquid meal) and fullness sensation (1.3±0.6 score increment; P=.031 vs liquid meal), but a markedly higher level of satisfaction (2.7±0.4 score increment; P=.021 vs liquid meal); the low-calorie mixed meal had less prominent effects with significantly lower satisfaction (1.0±0.4 score increment; P=.039 vs high-calorie meal).

CONCLUSIONS AND INFERENCES

The cognitive (satiation, fullness) and hedonic responses (satisfaction) to meals with equivalent levels of palatability, that is, equally likable, are dissociable. The characteristics of meals in terms of satiation and rewarding power could be adapted to specific clinical targets, whether nutritional supplementation or restriction.

Metabolic adaptation of colonic microbiota to galactooligosaccharides: a proof-of-concept-study

BACKGROUND

Prebiotics have been shown to reduce abdominal symptoms in patients with functional gut disorders, despite that they are fermented by colonic bacteria and may induce gas-related symptoms.

AIM

To investigate changes in the metabolic activity of gut microbiota induced by a recognised prebiotic.

METHODS

Healthy subjects (n = 20) were given a prebiotic (2.8 g/day HOST-G904, HOST Therabiomics, Jersey, Channel Islands) for 3 weeks. During 3-day periods immediately before, at the beginning and at the end of the administration subjects were put on a standard diet (low fibre diet supplemented with one portion of high fibre foods) and the following outcomes were measured: (i) number of daytime gas evacuations for 2 days by means of an event marker; (ii) volume of gas evacuated via a rectal tube during 4 h after a test meal; and (iii) microbiota composition by faecal Illumina MiSeq sequencing.

RESULTS

At the beginning of administration, HOST-G904 significantly increased the number of daily anal gas evacuations (18 ± 2 vs. 12 ± 1 pre-administration; P < 0.001) and the volume of gas evacuated after the test meal (236 ± 23 mL vs. 160 ± 17 mL pre-administration; P = 0.006). However, after 3 weeks of administration, these effects diminished (11 ± 2 daily evacuations, 169 ± 23 mL gas evacuation). At day 21, relative abundance of butyrate producers (Lachnospiraceae) correlated inversely with the volume of gas evacuated (r = -0.52; P = 0.02).

CONCLUSION

The availability of substrates induces an adaptation of the colonic microbiota activity in bacterial metabolism, which produces less gas and associated issues. Clinical trials.gov NCT02618239.

Cognitive and hedonic responses to meal ingestion correlate with changes in circulating metabolites

BACKGROUND

We have previously shown that meal ingestion induces cognitive perception (sensations) with a hedonic dimension (well-being) that depends on the characteristics of the meal and the appropriateness of the digestive response. The aim of the present study is to identify metabolomic biomarkers of the cognitive response to meal ingestion.

METHODS

In 18 healthy subjects, the response to a test meal (Edanec, 1 kcal/mL) ingested until maximum satiation (50 mL/min) was assessed. Perception measurements and blood samples were taken before, at the end of the meal, and 20 min after ingestion. The cognitive response and the hedonic dimension were measured on 10 cm scales. Metabolomic analysis was performed using nuclear magnetic resonance (NMR) spectroscopy and values of triglycerides, insulin, peptide YY (PYY), and glucagon-like peptide-1 (GLP-1) were determined using conventional laboratory techniques.

KEY RESULTS

Ingestion up to maximum satiation induced sensation of fullness and decreased digestive well-being. The total amount ingested by each subject correlated with the basal sensation of hunger, but not with other sensations or blood metabolite levels. Immediately after ingestion, satiation correlated with an increase in glucose (R = 0.49; p = 0.038) and valine levels (R = 0.48; p = 0.043). Twenty-minutes after finalizing ingestion, triglyceride levels had significantly increased which correlated with the recovery in well-being (R = 0.48; p = 0.046) and the decrease in desire to eat a food of choice (R = -0.56; p = 0.016). The increase in lipids inversely correlated with abdominal discomfort (R = -0.51; p = 0.032).

CONCLUSIONS & INFERENCES

Cognitive and hedonic responses to meal ingestion correlate with changes in circulating metabolites, which may serve as objective biomarkers of perception.

Randomized, Placebo-Controlled Trial of Biofeedback for the Treatment of Rumination

OBJECTIVES

We previously demonstrated that rumination is produced by an unperceived, somatic response to food ingestion, and we developed an original biofeedback technique based on electromyography (EMG)-guided control of abdomino-thoracic muscular activity. Our aim was to demonstrate the superiority of biofeedback vs. placebo for the treatment of rumination.

METHODS

Randomized, placebo-controlled trial performed in a referral center. Consecutive patients who fulfilled the Rome III criteria for rumination (18 women, 6 men; 19-79 years age) were selected and all included in the study; 1 patient assigned to placebo withdrew because of an unrelated accident. Abdomino-thoracic muscle activity after a challenge meal was recorded by EMG. The patients in the biofeedback group were shown the signal and instructed to control muscle activity, whereas the patients in the placebo group were not shown the signal and were given oral simethicone. Each patient underwent 3 sessions over a 10-day period.

MAIN OUTCOME

number of rumination events as measured by questionnaires for 10 consecutive days before and after intervention.

RESULTS

Patients on biofeedback (n=12) but not on placebo (n=11) effectively learned to reduce intercostal activity (by 51±6% vs. 10±7% increment on placebo; P<0.001) and anterior wall muscle activity (by 52±4% vs. 9±2% increment on placebo; P<0.001). Biofeedback treatment resulted in a 74±6% reduction in rumination activity (from 29±6 before to 7±2 daily events after intervention) vs. 1±14% on placebo; P=0.001 (from 21±2 before to 21±4 daily events after intervention).

CONCLUSIONS

Rumination can be effectively corrected by biofeedback-guided control of abdomino-thoracic muscular activity.

Ameliorating effect of transcutaneous electroacupuncture on impaired gastric accommodation induced by cold meal in healthy subjects

BACKGROUND

Impaired gastric accommodation is recognized as one of major pathophysiologies in functional dyspepsia and gastroparesis. Electroacupuncture has been shown to improve gastric accommodation in laboratory settings. It is, however, unknown whether it exerts similar ameliorating effect in humans and whether needleless transcutaneous electroacupuncture (TEA) is also effective in improving gastric accommodation.

AIM

The aim was to investigate the effects of TEA on gastric accommodation, gastric slow waves, and dyspeptic related symptoms.

METHODS

Thirteen healthy volunteers were studied in four randomized sessions: control, cold nutrient liquid, cold nutrient liquid + sham-TEA, and cold nutrient liquid + TEA. The subjects were requested to drink Ensure until reaching maximum satiety. The electrogastrogram (EGG) and electrocardiogram (ECG) were recorded to assess the gastric and autonomic functions respectively.

RESULTS

1) Gastric accommodation was reduced with the cold drink in comparison with the warm drink (P = 0.023). TEA improved the impaired gastric accommodation from 539.2 ± 133.8 ml to 731.0 ± 185.7 ml (P = 0.005). 2) The percentage of normal gastric slow waves in six subjects was significantly decreased in the cold session (P = 0.002) and improved in the TEA session (P = 0.009 vs sham; P < 0.001 vs cold). 3) TEA showed significant improvement in the bloating (80.8 ± 5.7 vs 61.2 ± 26.2, P = 0.011), postprandial fullness (48.1 ± 12.0 vs 34.2 ± 21.2, P = 0.042), and nausea (29.6 ± 10.9 vs 19.2 ± 11.2, P = 0.026) in comparison with sham-TEA session. 4) Neither cold drink nor TEA altered vagal activities (P > 0.05).

CONCLUSIONS

TEA improves impaired gastric accommodation and slow waves induced by cold drink and the effect does not seem to be mediated via the vagal mechanisms.

Fundamentals of Neurogastroenterology: Physiology/Motility - Sensation

The fundamental gastrointestinal functions include motility, sensation, absorption, secretion, digestion and intestinal barrier function. Digestion of food and absorption of nutrients normally occurs without conscious perception. Symptoms of functional gastrointestinal disorders are often triggered by meal intake suggesting abnormalities in the physiological processes are involved in the generation of symptoms. In this manuscript, normal physiology and pathophysiology of gastrointestinal function, and the processes underlying symptom generation are critically reviewed. The functions of each anatomical region of the digestive tract are summarized. The pathophysiology of perception, motility, mucosal barrier, and secretion in functional gastrointestinal disorders as well as effects of food, meal intake and microbiota on gastrointestinal motility and sensation are discussed. Genetic mechanisms associated with visceral pain and motor functions in health and functional gastrointestinal disorders are reviewed. Understanding the basis for digestive tract functions is essential to understand dysfunctions in the functional gastrointestinal disorders.

Functional dyspepsia

PURPOSE OF REVIEW

Structural causes are absent in more than 50% of patients with symptoms referred to the gastroduodenal region when routine diagnostic tests are applied. New knowledge holds the prospect that targeted therapy may more optimally manage subsets of these patients with functional dyspepsia.

RECENT FINDINGS

An understanding of gut-to-brain and brain-to-gut pathways in functional dyspepsia is expanding. Minimal mucosal inflammation with eosinophils (and in some cases mast cells) characterized by ultrastructural changes in the duodenum appears to be present in a substantial subgroup of functional dyspepsia patients as identified now by investigators globally. Although antibiotic therapy targeting Helicobacter pylori appears to be effective in a small proportion of functional dyspepsia patients, eradication therapy may be more effective in functional dyspepsia patients with microscopic duodenal inflammation, a potentially important finding needing to be confirmed. This may suggest that the effects of antibiotics for functional dyspepsia are not simply mediated by the eradication of gastric H. pylori, but have other antibacterial effects (e.g., on the duodenal microbiome). Abnormal visceral sensory function plays a key role not only in the manifestations of functional dyspepsia but also in peptic ulcer disease.

SUMMARY

The pathophysiologic concepts underlying functional dyspepsia and related treatment approaches are shifting from a focus on H. pylori, acid suppression or modulation of motility toward new models. New evidence suggests that minimal duodenal inflammation plays a role in symptom generation in at least a proportion of patients with otherwise unexplained symptoms. This is a paradigm shift and ultimately may change the treatment of many patients with functional gastrointestinal disorders.

Accumulative effect of food residues on intestinal gas production

BACKGROUND

As mean transit time in the colon is longer than the interval between meals, several consecutive meal loads accumulate, and contribute to colonic biomass. Our aim was to determine the summation effect of fermentable food residues on intestinal gas production.

METHODS

In eight healthy subjects, the volume of endogenous intestinal gas produced in the intestine over a 4-h period was measured by means of a wash-out technique, using an exogenous gas infusion into the jejunum (24 mL/min) and collection of the effluent via a rectal Foley catheter. The exogenous gas infused was labeled (5% SF6 ) to calculate the proportion of endogenous intestinal gas evacuated. In each subject, four experiments were performed ≥1 week apart combining a 1-day high- or low-flatulogenic diet with a test meal or fast.

KEY RESULTS

Basal conditions: on the low-flatulogenic diet, intestinal gas production during fasting over the 4-h study period was 609 ± 63 mL. Effect of diet: during fasting, intestinal gas production on the high-flatulogenic diet was 370 ± 146 mL greater than on the low-flatulogenic diet (p = 0.040). Effect of test meal: on the low-flatulogenic diet, intestinal gas production after the test meal was 681 ± 114 mL greater than during fasting (p = 0.001); a similar effect was observed on the high-flatulogenic diet (599 ± 174 mL more intestinal gas production after the test meal than during fasting; p = 0.021).

CONCLUSIONS & INFERENCES

Our data demonstrate temporal summation effects of food residues on intestinal gas production. Hence, intestinal gas production depends on pre-existing and on recent colonic loads of fermentable foodstuffs.

Abdominothoracic mechanisms of functional abdominal distension and correction by biofeedback

BACKGROUND & AIMS

In patients with functional gut disorders, abdominal distension has been associated with descent of the diaphragm and protrusion of the anterior abdominal wall. We investigated mechanisms of abdominal distension in these patients.

METHODS

We performed a prospective study of 45 patients (42 women, 24-71 years old) with functional intestinal disorders (27 with irritable bowel syndrome with constipation, 15 with functional bloating, and 3 with irritable bowel syndrome with alternating bowel habits) and discrete episodes of visible abdominal distension. Subjects were assessed by abdominothoracic computed tomography (n = 39) and electromyography (EMG) of the abdominothoracic wall (n = 32) during basal conditions (without abdominal distension) and during episodes of severe abdominal distension. Fifteen patients received a median of 2 sessions (range, 1-3 sessions) of EMG-guided, respiratory-targeted biofeedback treatment; 11 received 1 control session before treatment.

RESULTS

Episodes of abdominal distension were associated with diaphragm contraction (19% ± 3% increase in EMG score and 12 ± 2 mm descent; P < .001 vs basal values) and intercostal contraction (14% ± 3% increase in EMG scores and 6 ± 1 mm increase in thoracic antero-posterior diameter; P < .001 vs basal values). They were also associated with increases in lung volume (501 ± 93 mL; P < .001 vs basal value) and anterior abdominal wall protrusion (32 ± 3 mm increase in girth; P < .001 vs basal). Biofeedback treatment, but not control sessions, reduced the activity of the intercostal muscles (by 19% ± 2%) and the diaphragm (by 18% ± 4%), activated the internal oblique muscles (by 52% ± 13%), and reduced girth (by 25 ± 3 mm) (P ≤ .009 vs pretreatment for all).

CONCLUSIONS

In patients with functional gut disorders, abdominal distension is a behavioral response that involves activity of the abdominothoracic wall. This distension can be reduced with EMG-guided, respiratory-targeted biofeedback therapy.

Digestive, cognitive and hedonic responses to a meal

BACKGROUND

Gut dysfunctions may be associated to digestive symptoms. We hypothesized that the gut can also originate pleasant sensations, and wished to demonstrate the hedonic component of the digestive response to a meal.

METHODS

Healthy subjects (n = 42) were evaluated during basal fasting conditions and during experimentally induced fullness sensation (either by gastric distension or duodenal nutrient infusion). In each set of studies, a 240 mL test meal (12 kcal broth) and water, as inert control meal, were administered on separate days in a randomized, cross-over design. Gastric accommodation, the cognitive response and the hedonic dimension (both by 10 score scales) were measured 9 min before and 60 min after the meal.

KEY RESULTS

In basal conditions, the test meal induced a significantly greater gastric relaxation than the control meal (166 ± 28 mL isotonic volume increase 67 ± 14 mL; p = 0.002). Both meals induced epigastric fullness (3.8 ± 0.7 score and 3.2 ± 0.8 score, respectively; p = 0.740), but contrary to the inert meal, with the active meal this conscious sensation had a pleasant dimension (digestive comfort increase by 1.3 ± 0.6 score with active meal vs -1.1 ± 0.6 decrease with inert meal; p = 0.015). Experimentally induced fullness was associated to a decrease in digestive well-being or abdominal discomfort, which improved only after the active meal but not the inert meal.

CONCLUSIONS & INFERENCES

When appropriate conditions are met, the response to a meal includes a hedonic dimension involving pleasant sensation of digestive well-being.

Intestinal gas homeostasis: disposal pathways

BACKGROUND

Patients with functional gut disorders frequently complain of gas-related symptoms, but the role of intestinal gas in this context is not clear, because intestinal gas homeostasis is incompletely understood. Our aim was to compare the proportion of the gas produced by colonic fermentation that is evacuated per anus and that eliminated via alternative pathways.

METHODS

In 20 healthy subjects, gas evacuated per anus was collected for 4 h after a standard flatulogenic test meal. Paired studies were performed without and with high-rate infusion of exogenous gas (24 mL/min) into the jejunum to wash-out of the gut the endogenous gas produced by bacterial fermentation. The exogenous gas infused was labeled (5% SF₆) to calculate the proportion of endogenous gas evacuated.

KEY RESULTS

In the experiments with gaseous wash-out, 1817 ± 139 mL of endogenous gas was produced over the 4-h study period. However, in the experiments without wash-out (basal conditions), 376 ± 43 mL were evacuated, indicating that only 23 ± 3% of the gas produced was finally eliminated per anus, while the rest (77 ± 3%) had been previously eliminated via alternative pathways.

CONCLUSIONS & INFERENCES

Intestinal gas homeostasis is a highly dynamic process by which a large proportion of the gas produced by bacterial fermentation of meal residues is rapidly absorbed into the blood and/or metabolized by gas-consuming microorganisms, and only a relatively modest proportion is eliminated per anus. These data contribute to clarify the complex dynamics of intestinal gas and may help interpret the pathophysiology of gas-related symptoms.