Dyspepsia and the microbiome: time to focus on the small intestine

Association between gut microbiota and common overlapping gastrointestinal disorders: a bidirectional two-sample Mendelian randomization study

Background

The main functional gastrointestinal disorders (FGIDs) include functional dyspepsia (FD) and irritable bowel syndrome (IBS), which often present overlapping symptoms with gastroesophageal reflux disease (GERD), posing a challenge for clinical diagnosis and treatment. The gut microbiota is closely associated with FGIDs and GERD, although the causal relationship has not been fully elucidated. Therefore, we aimed to investigate the potential causal relationship using bidirectional two-sample Mendelian randomization (MR) analysis.

Materials and methods

The genetic data of the 211 gut microbiota were obtained from the MiBioGen consortium (N = 14,306, from phylum to genus level) and species level of gut microbiota were acquired from the Dutch Microbiome Project (N = 7,738). For FD and IBS, we utilized the FinnGen consortium, whereas, for GERD data analysis, we obtained the IEU OpenGWAS project. The inverse-variance weighted (IVW) method was used as the primary method to calculate causal effect values. Sensitivity analyses were also performed to confirm the robustness of the primary findings of the MR analyses. Moreover, a reverse MR analysis was conducted to assess the likelihood of reverse causality.

Results

Combining the results of the preliminary and sensitivity analyses, we identified that 8 gut microbial taxa were associated with FD. Genus Lachnospiraceae NK4A136 group (p = 3.63 × 10-3) and genus Terrisporobacter (p = 1.13 × 10-3) were strongly associated with FD. At the same time, we found that 8 gut microbial taxa were associated with IBS. Family Prevotellaceae (p = 2.44 × 10-3) and species Clostridium leptum (p = 7.68 × 10-3) display a robust correlation with IBS. In addition, 5 gut microbial taxa were associated with GERD using the IVW approach. In the reverse MR analysis, 2 gut microbial taxa were found to be associated with FD, 5 gut microbial taxa were found to be associated with IBS, and 21 gut microbial taxa were found to be associated with GERD.

Conclusion

The study reveals the potential causal effects of specific microbial taxa on FD, IBS, and GERD and may offer novel insights into the diagnosis and treatment of these conditions.

Microbiota modulation in disorders of gut-brain interaction

Disorders of gut-brain interaction (DGBI) are common chronic conditions characterized by persistent and recurring gastrointestinal symptoms triggered by several pathophysiological factors, including an altered gut microbiota. The most common DGBI are irritable bowel syndrome (IBS), functional constipation (FC) and functional dyspepsia (FD). Recently, a deep understanding of the role of the gut microbiota in these diseases was possible due to multi-omics methods capable to provide a comprehensive assessment. Most of the therapies recommended for these patients, can modulate the gut microbiota such as diet, prebiotics, probiotics and non-absorbable antibiotics, which were shown to be safe and effective. Since patients complain symptoms after food ingestion, diet represents the first line therapeutic approach. Avoiding dietary fat and fermentable oligosaccharides, disaccharides, monosaccharides, and polyols, and increasing the number of soluble fibers represent the therapeutic choices for FD, IBS and FC respectively. Probiotics, as a category, have been employed with good results in all the abovementioned DGBI. Rifaximin has been shown to be useful in the context of bowel related disorders, although a recent trial showed positive results for FD. Fecal microbiota transplantation has been tested for IBS and FC with promising results. In this review, we will briefly summarize the current understanding on dysbiosis and discuss microbiota modulation strategies to treat patients with DGBI.

Postprandial symptoms in disorders of gut-brain interaction and their potential as a treatment target

Postprandial, or meal-related, symptoms, such as abdominal pain, early satiation, fullness or bloating, are often reported by patients with disorders of gut-brain interaction, including functional dyspepsia (FD) or irritable bowel syndrome (IBS). We propose that postprandial symptoms arise via a distinct pathophysiological process. A physiological or psychological insult, for example, acute enteric infection, leads to loss of tolerance to a previously tolerated oral food antigen. This enables interaction of both the microbiota and the food antigen itself with the immune system, causing a localised immunological response, with activation of eosinophils and mast cells, and release of inflammatory mediators, including histamine and cytokines. These have more widespread systemic effects, including triggering nociceptive nerves and altering mood. Dietary interventions, including a diet low in fermentable oligosaccharides, disaccharides, monosaccharides and polyols, elimination of potential food antigens or gluten, IgG food sensitivity diets or salicylate restriction may benefit some patients with IBS or FD. This could be because the restriction of these foods or dietary components modulates this pathophysiological process. Similarly, drugs including proton pump inhibitors, histamine-receptor antagonists, mast cell stabilisers or even tricyclic or tetracyclic antidepressants, which have anti-histaminergic actions, all of which are potential treatments for FD and IBS, act on one or more of these mechanisms. It seems unlikely that food antigens driving intestinal immune activation are the entire explanation for postprandial symptoms in FD and IBS. In others, fermentation of intestinal carbohydrates, with gas release altering reflex responses, adverse reactions to food chemicals, central mechanisms or nocebo effects may dominate. However, if the concept that postprandial symptoms arise from food antigens driving an immune response in the gastrointestinal tract in a subset of patients is correct, it is paradigm-shifting, because if the choice of treatment were based on one or more of these therapeutic targets, patient outcomes may be improved.

Gut Bacteria Provide Genetic and Molecular Reporter Systems to Identify Specific Diseases

With genetic information gained from next-generation sequencing (NGS) and genome-wide association studies (GWAS), it is now possible to select for genes that encode reporter molecules that may be used to detect abnormalities such as alcohol-related liver disease (ARLD), cancer, cognitive impairment, multiple sclerosis (MS), diabesity, and ischemic stroke (IS). This, however, requires a thorough understanding of the gut-brain axis (GBA), the effect diets have on the selection of gut microbiota, conditions that influence the expression of microbial genes, and human physiology. Bacterial metabolites such as short-chain fatty acids (SCFAs) play a major role in gut homeostasis, maintain intestinal epithelial cells (IECs), and regulate the immune system, neurological, and endocrine functions. Changes in butyrate levels may serve as an early warning of colon cancer. Other cancer-reporting molecules are colibactin, a genotoxin produced by polyketide synthetase-positive Escherichia coli strains, and spermine oxidase (SMO). Increased butyrate levels are also associated with inflammation and impaired cognition. Dysbiosis may lead to increased production of oxidized low-density lipoproteins (OX-LDLs), known to restrict blood vessels and cause hypertension. Sudden changes in SCFA levels may also serve as a warning of IS. Early signs of ARLD may be detected by an increase in regenerating islet-derived 3 gamma (REG3G), which is associated with changes in the secretion of mucin-2 (Muc2). Pro-inflammatory molecules such as cytokines, interferons, and TNF may serve as early reporters of MS. Other examples of microbial enzymes and metabolites that may be used as reporters in the early detection of life-threatening diseases are reviewed.

Effect of Chaihu-Shugan-San on functional dyspepsia and gut microbiota: A randomized, double-blind, placebo-controlled trial

ETHNOPHARMACOLOGICAL RELEVANCE

Chaihu-Shugan-San (CSS) is a classic traditional Chinese medicine (TCM) formula from the Ming Dynasty "Jingyue's Complete Works". In China, it is prevalent for the treatment of a wide range of ailments, with a particular emphasis on functional gastrointestinal disorders (FGIDs). Clinical evidence suggests that CSS has been found to be a highly effective therapeutic approach for the treatment of Functional Dyspepsia (FD), however, there is a limited amount of high-quality clinical evidence, particularly randomized, double-blind, placebo-controlled trials to support this claim.

AIM OF THE STUDY

To evaluate the therapeutic efficacy of Chaihu-Shugan-San (CSS) for treating functional dyspepsia (FD) by comparing it to placebos, as well as to investigate the impact of CSS on the gut microbiota in individuals diagnosed with FD.

MATERIALS AND METHODS

This was a randomized double-blind, placebo-controlled clinical trial implemented at Shuguang Hospital in Shanghai. Between May 2021 and December 2022, 94 participants satisfying the Rome IV diagnostic criteria for FD were enrolled. They were assigned randomly to either the CSS group or the placebo group, with an equal allocation ratio of 1:1. Patients in both groups received the intervention for four weeks. The primary outcome was the dyspepsia symptom scores evaluated by using single dyspepsia symptom scale (SDS) after four weeks of treatment. The secondary outcomes were the solid gastric empties rate measured by a barium strip method, Hamilton anxiety scale (HAMA), Hamilton depression scale (HAMD), and Functional dyspepsia Quality of life scale (FDDQL). In addition, after unblinding, 30 patients in the CSS group were randomly selected and divided into before and after treatment of the FD groups (FD1, FD2), and 30 healthy participants were selected as healthy control group (HC), and the gut microbiota was analyzed by 16S rRNA sequencing.

RESULTS

After four weeks of treatment, the SDS score exhibited a significant improvement in the CSS group compared to the placebo group (t = 4.882; P ＜0.001). The difference in barium strip gastric emptying rate in the CSS group showed a significant ascent compared to the control group (P < 0.01). The HAMA, HAMD, and FDDQL scores in the CSS group showed a statistically significant increase compared to the control group (all P < 0.01). The results of 16S rRNA sequencing revealed that FD patients had less diverse and abundant microbiota than the healthy people. Additionally, the application of CSS resulted in the modulation of certain bacterial populations, leading to both up-regulation and down-regulation of their quantities.

CONCLUSIONS

These findings suggested that CSS is more effective compared to a placebo in treating FD, relieves anxiety and depression, increases gastric emptying rate in FD patients, and that CSS also affects the bacterial community structure in FD patients.

TRIAL REGISTRATION

ChiCTR, ChiCTR2100045793. Registered 25 Mach 2021.

The prevalence and risk factors of functional dyspepsia among adults in low- and middle-income countries: An international cross-sectional study

Dyspepsia is one of the most common chronic digestive diseases, which is due to underlying organic causes that can be detected, or causes that cannot be detected called functional dyspepsia (FD). There is no epidemiological study to date that measures the prevalence and risk factors of the FD in low- and middle-income countries, so this international cross-sectional study was conducted in 15 low- and middle-income countries from data previously published its protocol NCT05340400. Participants were recruited in the period from 22/April/2022 to 14/June/2022. The diagnosis of the FD was according to clinical manifestations. We determined the physical activity, daily stress, and fatigue of the participants. A large number of collaborators were chosen from different regions and institutions within each country to achieve diversity within the sample and reduce the probability of bias. Our study concluded that the prevalence of FD is much higher in low- and middle-income countries 37.9% [6.2%-44.2%], compared to high-income countries 10% [8%-12%], with a higher rate among the Afro-Caribbean race 47.9%. Sudan obtained the highest prevalence 44.3%, then Egypt 41.4%, while the lowest prevalence was in Algeria 25.7%. Moreover, there are many risk factors, including modifiable ones, such as severe stress, chronic fatigue, smoking, abnormal BMI, insufficient or too many hours of sleep, and previous infection with Covid-19, and non-modifiable ones such as advanced age, chronic diseases, and female sex. Highlighting the prevalence and increasing risk factors of FD in low- and middle-income countries should draw the attention of those responsible for health care in these countries and reduce the risk factors.

Proton pump inhibitors may enhance the risk of digestive diseases by regulating intestinal microbiota

Proton pump inhibitors (PPIs) are the most used acid-inhibitory drugs, with a wide range of applications in the treatment of various digestive diseases. However, recently, there has been a growing number of digestive complications linked to PPIs, and several studies have indicated that the intestinal flora play an important role in these complications. Therefore, developing a greater understanding of the role of the gut microbiota in PPI-related digestive diseases is essential. Here, we summarize the current research on the correlation between PPI-related digestive disorders and intestinal flora and establish the altered strains and possible pathogenic mechanisms of the different diseases. We aimed to provide a theoretical basis and reference for the future treatment and prevention of PPI-related digestive complications based on the regulation of the intestinal microbiota.

Spatial distribution of gut microbiota in mice during the occurrence and remission of hyperuricemia

BACKGROUND

Previous studies have shown that anserine can alleviate hyperuricemia by changing the fecal microbiota of hyperuricemic mice.

TOPIC

However, the fecal microbiota could not fully represent the distribution of the whole gut microbiota. Knowing the spatial distribution of the gastrointestinal tract microbiota is therefore important for understanding its action in the occurrence and remission of hyperuricemia.

METHODS

This study provides a comprehensive map of the most common bacterial communities that colonize different parts of the mouse gastrointestinal tract (stomach, duodenum, ileum, cecum, and colon) using a modern methodological approach.

RESULTS

The stomach, colon, and cecum showed the greatest richness and diversity in bacterial species. Three clusters of bacterial populations were observed along the digestive system: (1) in the stomach, (2) in the duodenum and ileum, and (3) in the colon and cecum. A high purine solution changed the composition and abundance of the digestive tract microbiota, and anserine relieved hyperuricemia by restoring the homeostasis of the digestive tract microbiota, especially improving the abundance of probiotics in the digestive tract.

IMPLICATION

This could be the starting point for further research on the regulation of hyperuricemia by gut microbiota with the ultimate goal of promoting health and welfare. © 2022 Society of Chemical Industry.

Gut Microbiome-Brain Alliance: A Landscape View into Mental and Gastrointestinal Health and Disorders

Gut microbiota includes a vast collection of microorganisms residing within the gastrointestinal tract. It is broadly recognized that the gut and brain are in constant bidirectional communication, of which gut microbiota and its metabolic production are a major component, and form the so-called gut microbiome-brain axis. Disturbances of microbiota homeostasis caused by imbalance in their functional composition and metabolic activities, known as dysbiosis, cause dysregulation of these pathways and trigger changes in the blood-brain barrier permeability, thereby causing pathological malfunctions, including neurological and functional gastrointestinal disorders. In turn, the brain can affect the structure and function of gut microbiota through the autonomic nervous system by regulating gut motility, intestinal transit and secretion, and gut permeability. Here, we examine data from the CAS Content Collection, the largest collection of published scientific information, and analyze the publication landscape of recent research. We review the advances in knowledge related to the human gut microbiome, its complexity and functionality, its communication with the central nervous system, and the effect of the gut microbiome-brain axis on mental and gut health. We discuss correlations between gut microbiota composition and various diseases, specifically gastrointestinal and mental disorders. We also explore gut microbiota metabolites with regard to their impact on the brain and gut function and associated diseases. Finally, we assess clinical applications of gut-microbiota-related substances and metabolites with their development pipelines. We hope this review can serve as a useful resource in understanding the current knowledge on this emerging field in an effort to further solving of the remaining challenges and fulfilling its potential.

Unravelling the controversy with small intestinal bacterial overgrowth

PURPOSE OF REVIEW

The aim of this review is to summarize the current and emergent approaches to characterize the small intestinal microbiota and discuss the treatment options for management of small intestinal bacterial overgrowth (SIBO).

RECENT FINDINGS

This review captures the growing body of evidence for the role of SIBO, a type of small intestinal dysbiosis in the pathophysiology various gastrointestinal and extraintestinal disorders. We have highlighted the drawbacks of the available methods for characterizing the small intestinal microbiota and focus on the new culture-independent techniques to diagnose SIBO. Although recurrence is common, targeted modulation of the gut microbiome as a therapeutic option for management of SIBO is associated with improvement in symptoms and quality of life.

SUMMARY

As a first step to precisely characterize the potential link between SIBO and various disorders, we need to address the methodological limitations of the available traditional tests for diagnosing SIBO. There is an urgency to develop culture independent techniques that can be routinely used in clinical setting, that will enable characterization of the gastrointestinal microbiome and explore the response to antimicrobial therapy including the links between long-lasting symptom resolution and the microbiome.

Gastroparesis: The Complex Interplay with Microbiota and the Role of Exogenous Infections in the Pathogenesis of the Disease

Gastroparesis (GP) is a disorder of gastric functions that is defined by objective delayed gastric emptying in the absence of mechanical obstruction. This disease is characterized by symptoms such as nausea, post-prandial fullness, and early satiety. GP significantly impacts patients' quality of life and contributes to substantial healthcare expenses for families and society. However, the epidemiological burden of GP is difficult to evaluate, mainly due its significant overlap with functional dyspepsia (FD). GP and FD represent two similar diseases. The pathophysiology of both disorders involves abnormal gastric motility, visceral hypersensitivity, and mucosal inflammation. Moreover, both conditions share similar symptoms, such as epigastric pain, bloating, and early satiety. The latest evidence reveals that dysbiosis is directly or indirectly connected to gut-brain axis alterations, which are the basis of pathogenesis in both FD and GP. Furthermore, the role of microbiota in the development of gastroparesis was demonstrated by some clinical studies, which found that the use of probiotics is correlated with improvements in the gastric emptying time (GET). Infections (with viruses, bacteria, and protozoa) represent a proven etiology for GP but have not been sufficiently considered in current clinical practice. Previous viral infections can be found in about 20% of idiopathic GP cases. Moreover, delayed gastric emptying during systemic protozoal infections represents a huge concern for compromised patients, and few data exist on the topic. This comprehensive narrative review analyzes the relationship between microorganisms and GP. We explore, on the one hand, the correlation between gut microbiota dysbiosis and GP pathogenesis, including treatment implications, and, on the other hand, the association between exogenous infections and the etiology of the disease.

Understanding neuroimmune interactions in disorders of gut-brain interaction: from functional to immune-mediated disorders

Functional gastrointestinal disorders-recently renamed into disorders of gut-brain interaction-such as irritable bowel syndrome and functional dyspepsia are highly prevalent conditions with bothersome abdominal symptoms in the absence of structural abnormalities. While traditionally considered as motility disorders or even psychosomatic conditions, our understanding of the pathophysiology has evolved significantly over the last two decades. Initial observations of subtle mucosal infiltration with immune cells, especially mast cells and eosinophils, are since recently being backed up by mechanistic evidence demonstrating increased release of nociceptive mediators by immune cells and the intestinal epithelium. These mediators can activate sensitised neurons leading to visceral hypersensitivity with bothersome symptoms. The interaction between immune activation and an impaired barrier function of the gut is most likely a bidirectional one with alterations in the microbiota, psychological stress and food components as upstream players in the pathophysiology. Only few immune-targeting treatments are currently available, but an improved understanding through a multidisciplinary scientific approach will hopefully identify novel, more precise treatment targets with ultimately better outcomes.

Comprehensive proteogenomic characterization of early duodenal cancer reveals the carcinogenesis tracks of different subtypes

The subtypes of duodenal cancer (DC) are complicated and the carcinogenesis process is not well characterized. We present comprehensive characterization of 438 samples from 156 DC patients, covering 2 major and 5 rare subtypes. Proteogenomics reveals LYN amplification at the chromosome 8q gain functioned in the transmit from intraepithelial neoplasia phase to infiltration tumor phase via MAPK signaling, and illustrates the DST mutation improves mTOR signaling in the duodenal adenocarcinoma stage. Proteome-based analysis elucidates stage-specific molecular characterizations and carcinogenesis tracks, and defines the cancer-driving waves of the adenocarcinoma and Brunner's gland subtypes. The drug-targetable alanyl-tRNA synthetase (AARS1) in the high tumor mutation burden/immune infiltration is significantly enhanced in DC progression, and catalyzes the lysine-alanylation of poly-ADP-ribose polymerases (PARP1), which decreases the apoptosis of cancer cells, eventually promoting cell proliferation and tumorigenesis. We assess the proteogenomic landscape of early DC, and provide insights into the molecular features corresponding therapeutic targets.

Targeting the altered duodenal microenvironment in functional dyspepsia

Duodenal micro-inflammation and microbial dysregulation are increasingly recognized to play an important role in functional dyspepsia (FD) pathophysiology, previously regarded as a purely functional disorder. With current therapeutic options contested through insufficient efficacy or unfavorable adverse effects profiles, novel treatments directed to duodenal alterations could result in superior symptom control in at least a subset of patients. Indeed, recent advances in FD research provided evidence for anti-inflammatory therapies to relieve gastroduodenal symptoms by reducing duodenal eosinophils or mast cells. In addition, restoring microbial homeostasis by probiotics proved to be successful in FD. As the exact mechanisms by which these novel pharmacological approaches result in clinical benefit often remain to be elucidated, future research should focus on how immune activation and dysbiosis translate into typical FD symptomatology.

Research trends in the field of the gut-brain interaction: Functional dyspepsia in the spotlight – An integrated bibliometric and science mapping approach

Objectives

This study aims to perform a bibliometric analysis of functional dyspepsia (FD), which includes visualizing bibliographic information, in order to identify prevailing study themes, topics of interest, contributing journals, countries, institutions, and authors as well as co-citation patterns.

Methods

The Web of Science™ Core Collection Database was used to retrieve all peer-reviewed scientific publications related to FD research. The validated search terms were entered into the “title” and “author keywords” fields, and the results were sorted by publication year from 2006 to 2022. There were no restrictions on language. On 12 February 2023, a manual export of the complete metadata for each original publication and review article was performed. CiteSpace was used to reveal co-authorship, publication, and co-citation patterns to find prominent authors, organizations, countries, and journals in FD research as well as to identify author keywords with strong citation bursts, which could indicate an emerging research area. VOSviewer was used to build the co-occurrence indicator (co-word) to identify the main author keywords on which previous studies focused and to induce clustered scientific landscape for two consecutive periods to identify intriguing areas for future research.

Results

A search of the database retrieved 2,957 documents. There was a wave-like pattern in the number of publications until 2017, after which there was a spike in publication volume. The USA, China, and Japan provided the majority of contributions. In terms of institution, Mayo Clin, Univ Newcastle, and Katholieke Univ Leuven were found to be the prolific institutions. Additionally, the results indicate that eastern Asian researchers contributed significantly to the global knowledge of literature that led other countries; however, Canada, the USA, Australia, England, and Germany were found to have the highest degree of betweenness centrality. Nicholas J. Talley, Jan Tack, Gerald Holtmann, Michael Camilleri, Ken Haruma, and Paul Moayyedi occupied the top positions based on productivity and centrality indicators. Six thematic clusters emerged (Helicobacter pylori infection; pathophysiological mechanisms of FD; extraintestinal co-morbidities and overlap syndromes associated with FD; herbal medicine in FD; diabetic gastroparesis; and dietary factors in FD). “Acupuncture,” “duodenal eosinophilia,” “gut microbiota,” and others were among the author keywords with rising prevalence.

Conclusion

In FD research, eastern Asian countries have established themselves as major contributors with the highest publishing productivity; however, research has primarily been driven by North America, Europe, and Australia, where cooperation is generally more active and highly influential scientific results are produced. Our analysis suggests that increased investments, training of human resources, improved infrastructures, and expanded collaborations are essential to improving the quality of FD research in Asia. The emerging author keyword analysis suggests that eosinophil-mast cell axis, gut microbiota, mental disorders, and acupuncture are the key areas that attract researchers’ attention as future research boulevards. There is a highly skewed distribution of research output across Asia, with most focus on complementary and alternative medicine (CAM) coming from Chinese, Japanese, and South Korean centers. However, CAM remains an underexplored area of research in the context of FD, and it deserves greater research efforts in order to obtain quality scientific evidence. Furthermore, we propose that the research framework of CAM should not be limited to dysmotility; rather, it could be interpreted within a more holistic context that includes the brain-gut-microbiota axis, as well as novel concepts such as duodenitis, increased mucosal permeability, and infiltration and activation of eosinophils and mast cells, among others. Overall, we provided bibliometrics-based overviews of relevant literature to researchers from different backgrounds and healthcare professionals to provide an in-depth overview of major trends in FD research.

Microbiota in the stomach and application of probiotics to gastroduodenal diseases

The stomach is a hostile environment for most microbes because strong gastric acid kills indigenous microorganisms. Thus, the mass of indigenous microbes detected by traditional culturing method in a highly acidic stomach is reported to be very small. However, in a stomach with less acidity due to atrophic changes of the gastric mucosa, the number of live gastric microbiota dramatically increases and their composition changes. A probiotic is defined as a live microorganism that, when administered in adequate amounts, confers a health benefit on the host. The administration of probiotics to the stomach has thus far been considered impractical, mainly due to the strong acidity in the stomach. The identification of candidate probiotic strains with sufficient resistance to acidity and the ability to achieve close proximity to the gastric mucosa could enable the application of probiotics to the stomach. The utilization of probiotics alone for Helicobacter pylori (H. pylori) infection significantly improves gastric mucosal inflammation and decreases the density of H. pylori on the mucosa, although complete eradication of H. pylori has not yet been demonstrated. The use of probiotics in combination with antimicrobial agents significantly increases the H. pylori eradication rate, especially when the H. pylori strains are resistant to antimicrobial agents. While H. pylori has been considered the most important pathogenic bacterium for the development of gastric cancer, bacteria other than H. pylori are also suggested to be causative pathogens that promote the development of gastric cancer, even after the eradication of H. pylori. Increased non-H. pylori Gram-negative bacteria in the stomach with weak acidity accompanying atrophic gastritis may perpetuate gastric mucosal inflammation and accelerate carcinogenic progression, even after H. pylori eradication. Probiotics restore the acidity in this stomach environment and may therefore prevent the development of gastric cancer by termination of Gram-negative bacteria-induced inflammation. Functional dyspepsia (FD) is defined as the presence of symptoms that are thought to originate in the gastroduodenal region in the absence of any organic, systematic or metabolic diseases. Accumulating evidence has pointed out the duodenum as a target region underlying the pathophysiology of FD. A randomized placebo-controlled clinical trial using a probiotic strain (LG21) demonstrated a significant improving effect on major FD symptoms. One of the possible mechanisms of this effect is protection of the duodenal mucosa from injurious intestinal bacteria through the resolution of small intestinal bacterial over growth.

The duodenal mucosa associated microbiome, visceral sensory function, immune activation and psychological comorbidities in functional gastrointestinal disorders with and without self-reported non-celiac wheat sensitivity

Frequently, patients with functional gastrointestinal disorders (FGIDs) report intolerance of wheat products. We compared gastrointestinal symptoms, sensory function, psychiatric comorbidities, gut-homing immune cells, and duodenal mucosa-associated microbiome (d-MAM) in FGID patients and controls with and without self-reported wheat sensitivity (SR-NCWS). We recruited 40 FGID patients and 20 controls referred by GPs for treatment. Gastrointestinal/extraintestinal symptoms, visceral sensory function, psychological comorbidities, and SR-NCWS were assessed in a standardized approach. Peripheral gut homing T-cells (CD4⁺α4⁺β7⁺CCR9⁺/CD8⁺α4⁺β7⁺CCR9⁺) were quantified, and the d-MAM was assessed by DNA sequencing for 46 subjects. Factors of bacterial genera were extracted utilizing factor analysis with varimax rotation and factors univariately associated with FGID or SR-NCWS included in a subsequent multivariate analysis of variance to identify statistically independent discriminators. Anxiety scores (p < .05) and increased symptom responses to a nutrient challenge (p < .05) were univariately associated with FGID. Gut homing T-cells were increased in FGID patients with SR-NCWS compared to other groups (p all <0.05). MANOVA revealed that anxiety (p = .03), visceral sensory function (p = 0.007), and a d-MAM factor comprise members of the Alloprevotella, Prevotella, Peptostreptococcus, Leptotrichia, and Veillonella lineages were significantly (p = .001) associated with FGID, while gut homing CD4⁺α4⁺ β7⁺CCR9⁺ T-cells were associated (p = .002) with SR-NCWS. Compared to controls, patients with and without SR-NCWS show that there are shifts in the amplicon sequence variants within specific bacterial genera between the FGID subgroups (particularly Prevotella and Streptococcus) as well as distinct bacterial taxa discriminatory for the two different FGID subtypes. Compared to controls, both FGID patients with and without SR-NCWS have an increased symptom response to a standardized nutrient challenge and increased anxiety scores. The FGID patients with SR-NCWS - as compared to FGID without SR-NCWS (and controls without SR-NCWS) - have increased gut homing T-cells. The d-MAM profiles suggest species and strain-based variations between the two FGID subtypes and in comparison to controls.

Role of the duodenal microbiota in functional dyspepsia

BACKGROUND

Functional dyspepsia (FD) is a common and debilitating gastrointestinal disorder attributed to altered gut-brain interactions. While the etiology of FD remains unknown, emerging research suggests the mechanisms are likely multifactorial and heterogenous among patient subgroups. Small bowel motor disturbances, visceral hypersensitivity, chronic microinflammation, and increased intestinal tract permeability have all been linked to the pathogenesis of FD. Recently, alterations to the gut microbiome have also been implicated to play an important role in the disease. Changes to the duodenal microbiota may either trigger or be a consequence of immune and neuronal disturbances observed in the disease, but the mechanisms of influence of small intestinal flora on gastrointestinal function and symptomatology are unknown.

PURPOSE

This review summarizes and synthesizes the literature on the link between the microbiota, low-grade inflammatory changes in the duodenum and FD. This review is not intended to provide a complete overview of FD or the small intestinal microbiota, but instead outline some of the key conceptual advances in understanding the interactions between altered gastrointestinal bacterial communities; dietary factors; host immune activation; and stimulation of the gut-brain axes in patients with FD versus controls. Current and emerging treatment approaches such as dietary interventions and antibiotic or probiotic use that have demonstrated symptom benefits for patients are reviewed, and their role in modulating the host-microbiota is discussed. Finally, suggested opportunities for diagnostic and therapeutic improvements for patients with this condition are presented.

Alterations to the duodenal microbiota are linked to gastric emptying and symptoms in functional dyspepsia

OBJECTIVE

Functional dyspepsia (FD) is a complex disorder, with debilitating epigastric symptoms. Evidence suggests alterations in gastrointestinal (GI) motility, visceral hypersensitivity, permeability and low-level immune activation in the duodenum may play a role. However, we still have a relatively poor understanding of how these factors interact to precipitate the onset of FD symptoms which are frequently meal related. The duodenal microbiota, in combination with specific dietary substrates, may be important mediators in disease pathophysiology; however, these interlinked factors have not been thoroughly investigated in FD.

DESIGN

Eighty-six individuals (56 FD, 30 controls) undergoing endoscopy were consecutively recruited and underwent detailed clinical assessment, including upper GI symptoms, gastric emptying and dietary assessment. Duodenal biopsies were obtained aseptically, and the mucosa-associated microbiota (MAM) analysed via 16S rRNA gene amplicon sequencing.

RESULTS

The relative abundances of predominant members of the Firmicutes, Bacteroidota and Fusobacteriota phyla were linked to symptom burden in FD. Inverse relationships between the relative abundances of Streptococcus and Prevotella, and the relative abundance of Veillonella spp with gastric emptying time, were also observed. No significant differences in long-term nutrient intake or diet quality were found between FD and controls, and there appeared to be limited association between habitual diet and duodenal MAM profiles.

CONCLUSION

This study suggests a link between the duodenal MAM, gastric emptying and FD symptoms, and this is largely independent of long-term dietary intake.

British Society of Gastroenterology guidelines on the management of functional dyspepsia

Functional dyspepsia (FD) is a common disorder of gut-brain interaction, affecting approximately 7% of individuals in the community, with most patients managed in primary care. The last British Society of Gastroenterology (BSG) guideline for the management of dyspepsia was published in 1996. In the interim, substantial advances have been made in understanding the complex pathophysiology of FD, and there has been a considerable amount of new evidence published concerning its diagnosis and classification, with the advent of the Rome IV criteria, and management. The primary aim of this guideline, commissioned by the BSG, is to review and summarise the current evidence to inform and guide clinical practice, by providing a practical framework for evidence-based diagnosis and treatment of patients. The approach to investigating the patient presenting with dyspepsia is discussed, and efficacy of drugs in FD summarised based on evidence derived from a comprehensive search of the medical literature, which was used to inform an update of a series of pairwise and network meta-analyses. Specific recommendations have been made according to the Grading of Recommendations Assessment, Development and Evaluation system. These provide both the strength of the recommendations and the overall quality of evidence. Finally, in this guideline, we consider novel treatments that are in development, as well as highlighting areas of unmet need and priorities for future research.

The Lumenal Microbiota Varies Biogeographically in the Gastrointestinal Tract of Rhesus Macaques

The strategy of adjusting the composition of gastrointestinal microbiota has shown great promise for the treatment of diseases. Currently, the relationship between gut microbes and human diseases is mainly presented by the fecal microbiota from the colon. Due to the limits of sampling, the healthy baseline of biogeographic microbiota in the human gastrointestinal tract remains blurry. Captive nonhuman primates (NHPs) present a "humanized" intestinal microbiome and may make up for the lack of atlas data for better understanding of the gut microbial composition and diseases. Therefore, the intestinal microbiota of 6 GIT regions of healthy rhesus monkeys were analyzed in this study; our results showed that Proteobacteria gradually decreased from the small intestine to the large intestine but Bacteroidetes gradually increased from the small intestine to the large intestine. Streptococcus and Lactobacillus can be used as markers to distinguish the small intestine from the large intestine. Sarcina is the most enriched in the middle site of the connection between the large intestine and the small intestine. Cyanobacteria are enriched in the small intestine, especially the duodenum and jejunum, and are absent in the large intestine. The lumenal microbiota of the small intestine is more susceptible to individual differences than is that of the large intestine. Metabolism and oxygen affect the distribution of the microbes, and the diversity of microbiota is the highest in the colon. Our results provide accurate comprehensive GIT microbiota data on nonhuman primates and will be beneficial for the better understanding of the composition of microbiota in the human gastrointestinal tract. IMPORTANCE For the study of upper gastrointestinal microbiota in humans, endoscopic sampling is the main source of information, which limits the understanding of healthy upper gastrointestinal microbiota. Rhesus monkeys show very close similarity to humans in physiology, genetics, and behavior and act as the most suitable animal models for human diseases. The present research made up for the lack of atlas data due to the ethical limitations of sampling in humans and provided baseline data on microbiota in 6 GIT regions of healthy NHPs. These important references will be beneficial for the better understanding of the regional organization and functions of gut microbial communities along the GIT and their relevance to conditions of health and disease.

The Role of Gastrointestinal Microbiota in Functional Dyspepsia: A Review

Functional dyspepsia is a clinically common functional gastrointestinal disorder with a high prevalence, high impact and high consumption of medical resources. The microbiota in the gastrointestinal tract is a large number of families and is one of the most complex microbial reservoirs in the human body. An increasing number of studies have confirmed the close association between dysbiosis of the gastrointestinal microbiota and the occurrence and progression of functional dyspepsia. Therefore, we reviewed the role of dysbiosis of the gastrointestinal microbiota, H. pylori infection and gastrointestinal microbiota metabolites in functional dyspepsia, focusing on the possible mechanisms by which dysbiosis of the gastrointestinal microbiota contributes to the pathogenesis of functional dyspepsia. Several studies have confirmed that dysbiosis of the gastrointestinal microbiota may cause the occurrence and progression of functional dyspepsia by disrupting the biological barrier of the intestinal mucosa, by disturbing the immune function of the intestinal mucosa, or by causing dysregulation of the microbial-gut-brain axis. Probiotics and antibiotics have also been chosen to treat functional dyspepsia in clinical studies and have shown some improvement in the clinical symptoms. However, more studies are needed to explore and confirm the relationship between dysbiosis of the gastrointestinal microbiota and the occurrence and progression of functional dyspepsia, and more clinical studies are needed to confirm the therapeutic efficacy of microbiota modulation for functional dyspepsia.

Evidence-Based and Emerging Diet Recommendations for Small Bowel Disorders

Diet plays a key role in the manifestation and severity of gastrointestinal symptoms, with increasing research interest on the role of diet in small bowel disorders. There are predominantly 3 small bowel conditions that have potential dietary interventions. Self-reported nonceliac gluten/wheat sensitivity is prevalent. Although gluten is believed to be a potential trigger for symptoms, other components of wheat may also be triggers, including fructans, alpha-amylase trypsin inhibitors, and wheat germ agglutinins. The diagnosis can be challenging, given the lack of validated biomarkers. A gluten-free diet that excludes the abovementioned triggers is the cornerstone of treatment; however, unlike celiac disease, there is uncertainty about the level of adherence or whether the gluten-free diet is a lifelong intervention. Several primary gastrointestinal disorders are associated with an increase in inflammatory cells including eosinophils. Diet seems to be an important driver of disease pathogenesis in eosinophilic gastroenteritis, with elimination and elemental diets showing promise in management, with further robust trials required. Small intestinal bacterial overgrowth is an example of microbial dysbiosis, with renewed interest in diet being postulated to cause an adaptive change of the microbes colonizing the small intestine. However, the diagnosis of small intestinal bacterial overgrowth is limited by a lack of sensitive and specific tests, with significant knowledge gaps in relation to therapeutic measures to manage and cure small intestinal bacterial overgrowth. Currently, antimicrobials are the established management option. There have been significant clinical advances in dietary interventions related to the small bowel, but this area is currently a novel and advancing field for both patients and clinicians.

Concomitant Irritable Bowel Syndrome Does Not Influence the Response to Antimicrobial Therapy in Patients with Functional Dyspepsia

BACKGROUND AND AIMS

Antimicrobial therapy improves symptoms in patients with irritable bowel syndrome (IBS), but the efficacy in functional dyspepsia (FD) is largely unknown. While FD and IBS frequently overlap, it is unknown if concomitant IBS in FD alters the response to antimicrobial therapy in FD. Thus, we aimed to assess and compare the effect of antimicrobial therapy on visceral sensory function and symptom improvement in FD patients with and without IBS.

METHODS

Adult patients with FD with or without IBS received rifaximin 550 mg BD for 10 days, followed by a 6-week follow-up period. The total gastrointestinal symptom score as measured by the SAGIS (Structured Assessment of Gastrointestinal Symptoms) questionnaire and subscores (dyspepsia, diarrhea, and constipation), symptom response to a standardized nutrient challenge and normalization of the glucose breath tests were measured.

RESULTS

Twenty-one consecutive adult patients with FD and 14/21 with concomitant IBS were recruited. Treatment with rifaximin resulted in a significant (p = 0.017) improvement in the total SAGIS score from 34.7 (± 15.4) at baseline to 26.0 (± 16.8) at 2 weeks and 25.6 (± 17.8) at 6 weeks post-treatment. Similarly, compared to baseline there was a statistically significant improvement in SAGIS subscores for dyspepsia and diarrhea (all p < 0.05) and effects persisted for 6 weeks post-treatment. Similarly, the symptom score (and subscores) following a standardized nutrient challenge improved significantly (p < 0.001) 2 weeks post-treatment. The presence of concomitant IBS did not significantly influence the improvement of symptoms after antibiotic therapy (all p > 0.5).

CONCLUSIONS

In FD patients, the response to antimicrobial therapy with rifaximin is not influenced by concomitant IBS symptoms.

Eosinophils, Hypoxia-Inducible Factors, and Barrier Dysfunction in Functional Dyspepsia

Functional dyspepsia (FD) is a highly prevalent disorder of gut-brain interaction (DGBI), previously known as a functional gastrointestinal disorder. Characterized by early satiety, postprandial fullness, and/or epigastric pain or burning, diagnosis depends on positive symptomatology and exclusion of obvious structural diseases. A subtle inflammatory phenotype has been identified in FD patients, involving an increase in duodenal mucosal eosinophils, and imbalances in the duodenal gut microbiota. A dysregulated epithelial barrier has also been well described in FD and is thought to be a contributing factor to the low-grade duodenal inflammation observed, however the mechanisms underpinning this are poorly understood. One possible explanation is that alterations in the microbiota and increased immune cells can result in the activation of cellular stress response pathways to perpetuate epithelial barrier dysregulation. One such cellular response pathway involves the stabilization of hypoxia-inducible factors (HIF). HIF, a transcriptional protein involved in the cellular recognition and adaptation to hypoxia, has been identified as a critical component of various pathologies, from cancer to inflammatory bowel disease (IBD). While the contribution of HIF to subtle inflammation, such as that seen in FD, is unknown, HIF has been shown to have roles in regulating the inflammatory response, particularly the recruitment of eosinophils, as well as maintaining epithelial barrier structure and function. As such, we aim to review our present understanding of the involvement of eosinophils, barrier dysfunction, and the changes to the gut microbiota including the potential pathways and mechanisms of HIF in FD. A combination of PubMed searches using the Mesh terms functional dyspepsia, functional gastrointestinal disorders, disorders of gut-brain interaction, duodenal eosinophilia, barrier dysfunction, gut microbiota, gut dysbiosis, low-grade duodenal inflammation, hypoxia-inducible factors (or HIF), and/or intestinal inflammation were undertaken in the writing of this narrative review to ensure relevant literature was included. Given the findings from various sources of literature, we propose a novel hypothesis involving a potential role for HIF in the pathophysiological mechanisms underlying FD.

Aqueous Extract of Phyllanthus emblica L. Alleviates Functional Dyspepsia through Regulating Gastrointestinal Hormones and Gut Microbiome In Vivo

Phyllanthus emblica L. fruits were extracted by a hot water assistant with ultrasonication to obtain aqueous Phyllanthus emblica L. extract (APE). The ameliorating functional dyspepsia (FD) effect of a low dose (150 mg/kg) and a high dose (300 mg/kg) of APE was exhibited by determining the gastrointestinal motility, gastrointestinal hormones, and gut microbiome shifts in reserpine induced FD male balb/c mice. APE increased the gastrointestinal motility including the gastric emptying (GE) rate and small intestinal transit (SIT) rate. The level of serum gastrointestinal hormones such as motilin (MTL) and gastrin (GAS) increased, and the vasoactive intestinal peptide (VIP) level decreased after the administration of APE. Furthermore, the gut microbiome analysis demonstrated that APE could regulate the microbiome structure and restore homeostasis by elevating useful bacterial abundance, while simultaneously decreasing harmful bacterial abundance. This study demonstrated the ameliorating FD effect of APE and its potential efficacy in curing functional gastrointestinal disorders and maintaining a healthy digestive tract.

Current and Future Approaches for Diagnosing Small Intestinal Dysbiosis in Patients With Symptoms of Functional Dyspepsia

The development and application of next generation sequencing technologies for clinical gastroenterology research has provided evidence that microbial dysbiosis is of relevance for the pathogenesis of gastrointestinal and extra-intestinal diseases. Microbial dysbiosis is characterized as alterations of diversity, function, and density of the intestinal microbes. Emerging evidence suggests that alterations of the gastrointestinal microbiome are important for the pathophysiology of a variety of functional gastrointestinal conditions, e.g., irritable bowel syndrome (IBS) and functional dyspepsia (FD), also known as disorders of brain-gut axis interaction. Clinicians have for many years recognized that small intestinal bacterial overgrowth (SIBO) is typified by a microbial dysbiosis that is underpinned by abnormal bacterial loads in these sites. SIBO presents with symptoms which overlap with symptoms of FD and IBS, point toward the possibility that SIBO is either the cause or the consequence of functional gastrointestinal disorders (FGIDs). More recently, new terms including “intestinal methanogen overgrowth” and “small intestinal fungal overgrowth” have been introduced to emphasize the contribution of methane production by archea and fungi in small intestinal dysbiosis. There is emerging data that targeted antimicrobial treatment of SIBO in patients with FD who simultaneously may or may not have IBS, results in symptom improvement and normalization of positive breath tests. However, the association between SIBO and FGIDs remains controversial, since widely accepted diagnostic tests for SIBO are lacking. Culture of jejunal fluid aspirate has been proposed as the “traditional gold standard” for establishing the diagnosis of SIBO. Utilizing jejunal fluid culture, the results can potentially be affected by cross contamination from oropharyngeal and luminal microbes, and there is controversy regarding the best cut off values for SIBO diagnosis. Thus, it is rarely used in routine clinical settings. These limitations have led to the development of breath tests, which when compared with the “traditional gold standard,” have sub-optimal sensitivity and specificity for SIBO diagnosis. With newer diagnostic approaches–based upon applications of the molecular techniques there is an opportunity to characterize the duodenal and colonic mucosa associated microbiome and associated gut microbiota dysbiosis in patients with various gastrointestinal and extraintestinal diseases. Furthermore, the role of confounders like psychological co-morbidities, medications, dietary practices, and environmental factors on the gastrointestinal microbiome in health and disease also needs to be explored.

The Potential Role of Hypochlorhydria in the Development of Duodenal Dysbiosis: A Preliminary Report

In recent years, the role of gastric and duodenal microbiota has acquired increasing importance in the homeostasis of the host, although, to date, most evidence concern the faecal microbiota. Indeed, the gastric, and duodenal microbiota are challenging to study, due to gastric acid, bile, digestive enzymes, and rapid transit time. Specifically, the gastric acid environment may influence their bacterial composition since the acid barrier protects against orally ingested microorganisms and leads to their inactivation before reaching the intestine. The aim of this study was to assess a correlation between intragastric pH and gastric as well as intestinal microbiota of patients with histologic gastric alterations. pH was measured in the gastric juice and the bacterial composition in gastric and duodenal biopsies and faecal samples, was investigated via 16s rRNA gene sequencing. The main result is the direct correlation of duodenal microbiota biodiversity, via alpha diversity measures, with intragastric pH values. In particular, patients with hypochlorhydria showed increased duodenal microbiota biodiversity, higher intragastric pH values being prevalent in patients with chronic atrophic gastritis. Lastly, the latter was also strongly associated to the presence of oral bacteria, like Rothia mucilaginosa, Streptococcus salivarius and Granulicatella adiacens, in the duodenal microbiota. In conclusions, our results suggest a low-acid gastric environment as a contributive factor for duodenal dysbiosis, potentially leading to the development of pathological conditions of the gastrointestinal tract.

[Duodenal Microbiome and Its Clinical Implications in Functional Dyspepsia]

Functional dyspepsia is one of the most common functional gastrointestinal disorders with chronic bothersome epigastric pain or postprandial fullness without a definite organic cause. Despite its high clinical burden, the treatment modalities for modulating impaired motor dysfunction and visceral hypersensitivity have been unsatisfactory. Recently, studies demonstrating low-grade inflammation and dysbiosis of the duodenal mucosa as potential triggers of the disease have attracted attention. Observations, such as an increase in the proportion of oral commensal bacteria in the duodenal mucosa, such as Streptococcus species, highlight the importance of bacterial ecology in developing symptoms of functional dyspepsia. In the near future, anti-inflammatory drugs and probiotics that modulate the host-microbiome interaction are expected to emerge to treat functional dyspepsia.

Circadian Rhythms and Melatonin Metabolism in Patients With Disorders of Gut-Brain Interactions

Circadian rhythms are cyclic patterns of physiological, behavioural and molecular events that occur over a 24-h period. They are controlled by the suprachiasmatic nucleus (SCN), the brain’s master pacemaker which governs peripheral clocks and melatonin release. While circadian systems are endogenous, there are external factors that synchronise the SCN to the ambient environment including light/dark cycles, fasting/fed state, temperature and physical activity. Circadian rhythms also provide internal temporal organisation which ensures that any internal changes that take place are centrally coordinated. Melatonin synchronises peripheral clocks to the external time and circadian rhythms are regulated by gene expression to control physiological function. Synchronisation of the circadian system with the external environment is vital for the health and survival of an organism and as circadian rhythms play a pivotal role in regulating GI physiology, disruption may lead to gastrointestinal (GI) dysfunction. Disorders of gut-brain interactions (DGBIs), also known as functional gastrointestinal disorders (FGIDs), are a group of diseases where patients experience reoccurring gastrointestinal symptoms which cannot be explained by obvious structural abnormalities and include functional dyspepsia (FD) and irritable bowel syndrome (IBS). Food timing impacts on the production of melatonin and given the correlation between food intake and symptom onset reported by patients with DGBIs, chronodisruption may be a feature of these conditions. Recent advances in immunology implicate circadian rhythms in the regulation of immune responses, and DGBI patients report fatigue and disordered sleep, suggesting circadian disruption. Further, melatonin treatment has been demonstrated to improve symptom burden in IBS patients, however, the mechanisms underlying this efficacy are unclear. Given the influence of circadian rhythms on gastrointestinal physiology and the immune system, modulation of these rhythms may be a potential therapeutic option for reducing symptom burden in these patients.

Defects in NLRP6, autophagy and goblet cell homeostasis are associated with reduced duodenal CRH receptor 2 expression in patients with functional dyspepsia

Functional dyspepsia (FD) affects up to 15% of the population and is characterised by recurring upper gastrointestinal (GI) symptoms occurring in the absence of clinically identifiable pathology. Psychological stress is a key factor associated with the onset of FD and locally acting hypothalamic-pituitary-adrenal (HPA) axis hormones have been implicated in GI motility and barrier dysfunction. Recent pre-clinical work has identified mechanistic pathways linking corticotropin-releasing hormone (CRH) with the innate epithelial immune protein NLRP6, an inflammasome that has been shown to regulate GI mucus secretion. We recruited twelve FD patients and twelve healthy individuals to examine whether dysregulation of hypothalamic-pituitary adrenal (HPA) axis hormones and altered NLRP6 pathways were evident in the duodenal mucosa. Protein expression was assessed by immunoblot and immunohistochemistry in D2 duodenal biopsies. Plasma HPA axis hormones were assayed by ELISA and enteroid and colorectal cancer cell line cultures were used to verify function. FD patients exhibited reduced duodenal CRH-receptor 2, compared to non-GI disease controls, indicating a dysregulation of duodenal HPA signalling. The loss of CRH-receptor 2 correlated with reduced NLRP6 expression and autophagy function, processes critical for maintaining goblet cell homeostasis. In accordance, duodenal goblet cell numbers and mucin exocytosis was reduced in FD patients compared to controls. In vitro studies demonstrated that CRH could reduce NLRP6 in duodenal spheroids and promote mucus secretion in the HT29-MTX-E12 cell line. In conclusion, FD patients exhibit defects in the NLRP6-autophagy axis with decreased goblet cell function that may drive symptoms of disease. These features correlated with loss of CRH receptor 2 and may be driven by dysregulation of HPA signalling in the duodenum of FD patients.

Bi-Directionality of the Microbiota-Gut-Brain Axis in Patients With Functional Dyspepsia: Relevance of Psychotherapy and Probiotics

Functional dyspepsia is one of the most commonly diagnosed disorders of the gut-brain interaction worldwide. The precise pathogenesis of functional dyspepsia is complex and remains incompletely understood. Therefore, advances in the understanding of functional dyspepsia could change clinical practice. The aim of this review is to highlight the relevance of psychotherapy and probiotics in the context of the microbiota-gut-brain axis in the pathophysiology and especially in the treatment of functional dyspepsia. Therefore, studies which have been conducted to investigate the role of psychotherapy and probiotics in FD and the microbiota-gut-brain axis in the pathophysiology of functional dyspepsia were examined, and the outcomes of this research summarized. There might be a link between changes in the microbiome and functional dyspepsia. Even though, specific alterations in the microbiome that may be pathognomonic in functional dyspepsia remain unclear, the use of probiotics became a viable treatment option for patients with functional dyspepsia. Since mental illness also plays an important role in the pathophysiology of functional dyspepsia, psychotherapy is a useful treatment method, with additional study results indicating that psychotherapy may also shift the microbiome in a favorable direction. Moreover, other findings suggest that probiotics can be used not only to alleviate gastrointestinal symptoms in functional dyspepsia, but also to treat or even prevent mental disorders in these patients. In summary, in this review we highlight the bi-directionality of the microbiota-gut-brain axis in the pathophysiology of functional dyspepsia. Although there are multiple treatment approaches, the burden of disease in patients with functional dyspepsia is still enormous and a definitive therapy to cure this disease does not (yet) exist. Lastly, there is a lack of studies on the impact of dysbiosis, mental health and probiotics on pathophysiology and symptomatology in functional dyspepsia which should be investigated in future studies.

Efficacy of Helicobacter pylori eradication therapy for functional dyspepsia: updated systematic review and meta-analysis

OBJECTIVE

Functional dyspepsia (FD) is a chronic disorder that is difficult to treat. Helicobacter pylori may contribute to its pathophysiology. A Cochrane review from 2006 suggested that eradication therapy was beneficial, but there have been numerous randomised controlled trials (RCTs) published since. We evaluated impact of eradication therapy on both cure and improvement of FD, as well as whether any benefit was likely to arise from eradication of H. pylori.

DESIGN

We searched the medical literature through October 2021 to identify RCTs examining efficacy of eradication therapy in H. pylori-positive adults with FD. The control arm received antisecretory therapy or prokinetics, with or without placebo antibiotics, or placebo alone. Follow-up was for ≥3 months. We pooled dichotomous data to obtain a relative risk (RR) of symptoms not being cured or symptoms not improving with a 95% CI. We estimated the number needed to treat (NNT).

RESULTS

Twenty-nine RCTs recruited 6781 H. pylori-positive patients with FD. Eradication therapy was superior to control for symptom cure (RR of symptoms not being cured=0.91; 95% CI 0.88 to 0.94, NNT=14; 95% CI 11 to 21) and improvement (RR of symptoms not improving=0.84; 95% CI 0.78 to 0.91, NNT=9; 95% CI 7 to 17). There was no significant correlation between eradication rate and RR of FD improving or being cured (Pearson correlation coefficient=-0.23, p=0.907), but the effect was larger in patients with successful eradication of H. pylori than with unsuccessful eradication (RR=0.65; 95% CI 0.52 to 0.82, NNT=4.5, 95% CI 3 to 9). Adverse events (RR=2.19; 95% 1.10 to 4.37) and adverse events leading to withdrawal (RR=2.60; 95% CI 1.47 to 4.58) were more common with eradication therapy.

CONCLUSION

There is high quality evidence to suggest that H. pylori eradication therapy leads to both cure and improvement in FD symptoms, although the benefit is modest.

Duodenal microbiota makes an important impact in functional dyspepsia

Duodenal microbiota may have impact in Functional Dyspepsia. The aim of this study was to explore the difference of microbiota on duodenal mucosa between patients with Functional Dyspepsia and normal subjects. The duodenal mucosa of the subjects were collected under upper gastrointestinal endoscope and the contents of the descending duodenal intestine were extracted with cell brushes in 20 patients with Functional Dyspepsia and 5 healthy subjects. The microbiome on duodenal was studied by 16SrDNA gene sequencing. The differences of duodenal flora were analyzed and compared by LEfSe, FAPROTAX, SPSS and other software. There were significant differences in ACE index, shannon index and observedspecies index between patients with functional dyspepsia and healthy people (P < 0.05). PCoA analysis of the structure of bacteria between two groups found that the duodenal microbiome showed a separate trend. In further study, Amova analysis showed a significant difference (P < 0.05). We found that the there are obvious differences in the composition of duodenal microbiome in functional dyspepsia and healthy people. At the genus level, there were significant differences in Alloprevotella, Peptostreptococcus,Sutterella, Corynebacteriurn,Catonella, Faecalibacterium,Staphylococcus,Eubacteriumnodatumgro-up, Lachnoclostridiurn and Lautropia between the two groups (P < 0.05). The prediction results of Microflora function from FAPROTAX showed that the urea decomposing (ureolysis) and fumaric acid respiratory (fumaraterespiration) function of duodenal bacteria in patients with functional dyspepsia were significantly different from those in healthy people (P < 0.05). In conclusion, there is a significant difference in mucosal microflora of duodenum between patients with functional dyspepsia and healthy groups. It includes greater microflora diversity, different microflora structure, different microflora composition, specific taxa and specific microbiome function. The disorder of duodenal microecology may be the formation mechanism of functional dyspepsia.

Duodenal Dysbiosis and Relation to the Efficacy of Proton Pump Inhibitors in Functional Dyspepsia

Proton pump inhibitors (PPI) may improve symptoms in functional dyspepsia (FD) through duodenal eosinophil-reducing effects. However, the contribution of the microbiome to FD symptoms and its interaction with PPI remains elusive. Aseptic duodenal brushings and biopsies were performed before and after PPI intake (4 weeks Pantoprazole 40 mg daily, FD-starters and controls) or withdrawal (2 months, FD-stoppers) for 16S-rRNA sequencing. Between- and within-group changes in genera or diversity and associations with symptoms or duodenal factors were analyzed. In total, 30 controls, 28 FD-starters and 19 FD-stoppers were followed. Mucus-associated Porphyromonas was lower in FD-starters vs. controls and correlated with symptoms in FD and duodenal eosinophils in both groups, while Streptococcus correlated with eosinophils in controls. Although clinical and eosinophil-reducing effects of PPI therapy were unrelated to microbiota changes in FD-starters, increased Streptococcus was associated with duodenal PPI effects in controls and remained higher despite withdrawal of long-term PPI therapy in FD-stoppers. Thus, duodenal microbiome analysis demonstrated differential mucus-associated genera, with a potential role of Porphyromonas in FD pathophysiology. While beneficial effects of short-term PPI therapy were not associated with microbial changes in FD-starters, increased Streptococcus and its association with PPIeffects in controls suggest a role for duodenal dysbiosis after long-term PPI therapy.

Systematic Survey of the Alteration of the Faecal Microbiota in Rats With Gastrointestinal Disorder and Modulation by Multicomponent Drugs

Gastrointestinal disorder (GID) is a global health disease which leads to heavy public medical burden. Disorders in the intestinal flora have been found in gastrointestinal disorder patients. However, the interaction between GID and the intestinal flora in faecal has not been studied comprehensively. In addition, multicomponent drugs represented by traditional Chinese medicine (TCM) are widely used for treating GID, but their modulation of the intestinal flora has not been investigated. Therefore, in this study, a high-throughput sequencing strategy was used to investigate alterations in the intestinal flora in a rat GID model, followed by an investigation of the modulation by a representative TCM, Xiaoerfupi (XEFP) granule. The results showed that in rats with GID, the relative abundances of Erysipelotrichaceae, Lachnospiraceae, Streptococcaceae increased and that of Ruminococcaceae decreased. At the macro level, the levels of LysoPC(16:0), LysoPC(20:2), LysoPC(15:0), LysoPC(20:2 (11Z, 14Z)), LysoPC(20:1), LysoPC(15:0), LysoPC(20:0) and LysoPE (0:0/20:0) in serum increased and levels of PC(36:4), PC(38:4), PC(o-36;4), PE (MonoMe(13,5)/MonoMe(11,5)) decreased. The imbalance of metabolites was restored by XEFP through ether lipid metabolism pathway. Increase in the phyla Firmicutes/Bacteroidetes (F/B) ratio of the GID rats was restored by XEFP as well. Moreover, XEFP can relief the symptoms of GID rats by increasing bacteria Ruminococcaceae and decreasing Streptococcaceae, Erysipelotrichaceae and Lachnospiraceae in faecal microbiota level. This study represents a comprehensive survey of the interaction between GID and the intestinal flora and a systematic evaluation of modulation by a multicomponent drug.

Physiological mechanisms of unexplained (functional) gastrointestinal disorders

Functional gastrointestinal disorders (FGIDs) encompass a range of complex conditions with similar clinical characteristics and no overt pathology. Recent recognition of sub-clinical pathologies in FGIDs, in conjunction with physiological and biochemical abnormalities including increased intestinal permeability, microbial profile alterations, differences in metabolites and extra-intestinal manifestations of disease, call into question the designation of these conditions as 'functional'. This is despite significant heterogeneity in both symptom profile and specifics of reported physiological abnormalities hampering efforts to determine defined mechanisms that drive onset and chronicity of symptoms. Instead, the literature demonstrates these conditions are disorders of homeostatic imbalance, with disruptions in both host and microbial function and metabolism. This imbalance is also associated with extraintestinal abnormalities including psychological comorbidities and fatigue that may be a consequence of gastrointestinal disruption. Given the exploitation of such abnormalities will be crucial for improved therapeutic selection, an enhanced understanding of the relationship between alterations in function of the gastrointestinal tract and the response of the immune system is of interest in identifying mechanisms that drive FGID onset and chronicity. Considerations for future research should include the role of sex hormones in regulating physiological functions and treatment responses in patients, as well as the importance of high-level phenotyping of clinical, immune, microbial and physiological parameters in study cohorts. There is opportunity to examine the functional contribution of the microbiota and associated metabolites as a source of mechanistic insight and targets for therapeutic modulation.

Role of microRNAs in Disorders of Gut-Brain Interactions: Clinical Insights and Therapeutic Alternatives

Disorders of gut–brain interactions (DGBIs) are heterogeneous in nature and intertwine with diverse pathophysiological mechanisms. Regular functioning of the gut requires complex coordinated interplay between a variety of gastrointestinal (GI) cell types and their functions are regulated by multiple mechanisms at the transcriptional, post-transcriptional, translational, and post-translational levels. MicroRNAs (miRNAs) are small non-coding RNA molecules that post-transcriptionally regulate gene expression by binding to specific mRNA targets to repress their translation and/or promote the target mRNA degradation. Dysregulation of miRNAs might impair gut physiological functions leading to DGBIs and gut motility disorders. Studies have shown miRNAs regulate gut functions such as visceral sensation, gut immune response, GI barrier function, enteric neuronal development, and GI motility. These biological processes are highly relevant to the gut where neuroimmune interactions are key contributors in controlling gut homeostasis and functional defects lead to DGBIs. Although extensive research has explored the pathophysiology of DGBIs, further research is warranted to bolster the molecular mechanisms behind these disorders. The therapeutic targeting of miRNAs represents an attractive approach for the treatment of DGBIs because they offer new insights into disease mechanisms and have great potential to be used in the clinic as diagnostic markers and therapeutic targets. Here, we review recent advances regarding the regulation of miRNAs in GI pacemaking cells, immune cells, and enteric neurons modulating pathophysiological mechanisms of DGBIs. This review aims to assess the impacts of miRNAs on the pathophysiological mechanisms of DGBIs, including GI dysmotility, impaired intestinal barrier function, gut immune dysfunction, and visceral hypersensitivity. We also summarize the therapeutic alternatives for gut microbial dysbiosis in DGBIs, highlighting the clinical insights and areas for further exploration. We further discuss the challenges in miRNA therapeutics and promising emerging approaches.

Duodenal eosinophilia and the link to anxiety: A population-based endoscopic study

INTRODUCTION

The concept of gut-to-brain communication via microbial or inflammatory pathways is gaining increased attention but genuine pathology directly linking gut perturbation to anxiety is lacking. We hypothesized that duodenal eosinophilia, as known to occur in functional dyspepsia (FD), may be an underlying cause of anxiety and may help explain the striking association between FD and anxiety.

METHODS

Randomly selected subjects from the national population register of Sweden completed the validated Abdominal Symptom Questionnaire; 1000 completed esophagogastroduodenoscopy and the Hospital Anxiety and Depression Scale questionnaire. Duodenal biopsies were obtained from 1^st (D1) and 2^nd portion (D2). Eligible subjects who underwent endoscopy (n = 887) were invited to participate in a 10-year follow-up study with the same questionnaires. Among endoscopy normal subjects, FD was identified by Rome criteria, and controls were symptom free. Duodenal eosinophilia was based on pre-defined cut-offs. Finding are reported as odds ratios (ORs) with 95% confidence interval and p-value.

RESULTS

The study population comprised 89 cases with FD and 124 healthy controls (mean age 62 years, SD 12, 34% male). Clinical anxiety at follow-up was elevated in those with D1 eosinophilia at baseline considering either new-onset anxiety (OR = 4.5, 95% CI 0.8, 23.8; p = 0.08) or follow-up anxiety adjusting for baseline anxiety (OR = 4.51 (95% CI 1.03, 19.81; p = 0.046).

CONCLUSION

Duodenal eosinophilia may potentially be a mechanism linked to anxiety independent of FD.

Draft Genome Sequence of Streptococcus salivarius AGIRA0003, Isolated from Functional Gastrointestinal Disorder Duodenal Tissue

Patients suffering functional dyspepsia symptoms have been shown to possess a greater relative abundance of Streptococcus compared to asymptomatic controls. Here, we describe the isolation and genomic features of a new Streptococcus isolate, from the duodenal tissue of a subject reporting dyspeptic symptoms, taxonomically assigned to Streptococcus salivarius and designated strain AGIRA0003.

Gut microbiota dysbiosis in functional gastrointestinal disorders: Underpinning the symptoms and pathophysiology

Functional gastrointestinal disorders (FGIDs), currently known as disorders of gut-brain interaction, are emerging microbiota-gut-brain abnormalities that are prevalent worldwide. The pathogenesis of FGIDs is heterogeneous and is intertwined with gut microbiota and its derived molecule-modulated mechanisms, including gut dysmotility, visceral hypersensitivity, gut immune abnormalities, abnormal secretion, and impaired barrier function. There has been phenomenal progress in understanding the role of gut microbiota in FGIDs by underpinning the species alternations between healthy and pathological conditions such as FGIDs. However, the precise gut microbiota-directed cellular and molecular pathogeneses of FGIDs are yet enigmatic. Determining the mechanistic link between the gut microbiota and gastrointestinal (GI) diseases has been difficult due to (i) the lack of robust animal models imitating the various aspects of human FGID pathophysiology; (ii) the absence of longitudinal human and/or animal studies to unveil the interaction of the gut microbiota with FGID-relevant pathogenesis; (iii) uncertainty about connections between human and animal studies; and (iv) insufficient data supporting a holistic view of disease-specific pathophysiological changes in FGID patients. These unidentified gaps open possibilities to explore pathological mechanisms directed through gut microbiota dysbiosis in FGIDs. The current treatment options for dysbiotic gut microbiota are limited; dietary interventions, antibiotics, probiotics, and fecal microbiota transplantation are the front-line clinical options. Here, we review the contribution of gut microbiota and its derived molecules in gut homeostasis and explore the possible pathophysiological mechanisms involved in FGIDs leading to potential therapeutics options.

United European Gastroenterology (UEG) and European Society for Neurogastroenterology and Motility (ESNM) consensus on functional dyspepsia

BACKGROUND

Functional dyspepsia (FD) is one of the most common conditions in clinical practice. In spite of its prevalence, FD is associated with major uncertainties in terms of its definition, underlying pathophysiology, diagnosis, treatment, and prognosis.

METHODS

A Delphi consensus was initiated with 41 experts from 22 European countries who conducted a literature summary and voting process on 87 statements. Quality of evidence was evaluated using the grading of recommendations, assessment, development, and evaluation (GRADE) criteria. Consensus (defined as >80% agreement) was reached for 36 statements.

RESULTS

The panel agreed with the definition in terms of its cardinal symptoms (early satiation, postprandial fullness, epigastric pain, and epigastric burning), its subdivision into epigastric pain syndrome and postprandial distress syndrome, and the presence of accessory symptoms (upper abdominal bloating, nausea, belching), and overlapping conditions. Also, well accepted are the female predominance of FD, its impact on quality of life and health costs, and acute gastrointestinal infections, and anxiety as risk factors. In terms of pathophysiological mechanisms, the consensus supports a role for impaired gastric accommodation, delayed gastric emptying, hypersensitivity to gastric distention, Helicobacter pylori infection, and altered central processing of signals from the gastroduodenal region. There is consensus that endoscopy is mandatory for establishing a firm diagnosis of FD, but that in primary care, patients without alarm symptoms or risk factors can be managed without endoscopy. There is consensus that H. pylori status should be determined in every patient with dyspeptic symptoms and H. pylori positive patients should receive eradication therapy. Also, proton pump inhibitor therapy is considered an effective therapy for FD, but no other treatment approach reached a consensus. The long-term prognosis and life expectancy are favorable.

CONCLUSIONS AND INFERENCES

A multinational group of European experts summarized the current state of consensus on the definition, diagnosis and management of FD.

Functional dyspepsia: A critical appraisal of the European consensus from a global perspective

The European Society for Neurogastroenterology and Motility's (ESNM) consensus document on functional dyspepsia (FD) has provided a critical review of the evidence for 36 statements highly relevant to the diagnosis and treatment of FD. We provide here our expert opinion on the North American, Australian and Asian assessments of the same topics discussed, and provide evidence where the ESNM consensus may deviate from those in the other continents. New and exciting data about the pathogenesis of FD are emerging including the possible central role of duodenal micro-inflammation (most notably eosinophilic duodenitis and intestinal mast cell disease), but this is a very dynamic field with several gaps remaining in our understanding that are summarized in this review. Identification of non-invasive biomarkers and testing of targeted therapies, including assessing the benefits of multidisciplinary teams in the management of FD, should be future priorities.

The Usefulness of Symptom-based Subtypes of Functional Dyspepsia for Predicting Underlying Pathophysiologic Mechanisms and Choosing Appropriate Therapeutic Agents

Functional dyspepsia (FD) is considered to be a heterogeneous disorder with different pathophysiological mechanisms or pathogenetic factors. In addition to traditional mechanisms, novel concepts regarding pathophysiologic mechanisms of FD have been proposed. Candidates of therapeutic agents based on novel concepts have also been suggested. FD is a symptom complex and currently diagnosed by symptom-based Rome criteria. In the Rome criteria, symptom-based subtypes of FD including postprandial distress syndrome and epigastric pain syndrome are recommended to be used, based on the assumption that each subtype is more homogenous in terms of underlying pathophysiologic mechanisms than FD as a whole. In this review, the usefulness of symptombased subtypes of FD for predicting underlying pathophysiologic mechanisms and choosing appropriate therapeutic agents was evaluated. Although several classic pathophysiologic mechanisms are suggested to be associated with individual dyspeptic symptoms, symptom-based subtypes of FD are not specific for a certain pathogenetic factor or pathophysiologic mechanism, and may be frequently associated with multiple pathophysiologic abnormalities. Novel concepts on the pathophysiology of FD show complex interactions between pathophysiologic mechanisms and pathogenetic factors, and prediction of underlying mechanisms of individual patients simply by the symptom pattern or symptom-based subtypes may not be accurate in a considerable proportion of cases. Therefore, subtyping by the Rome criteria appears to have limited value to guide therapeutic strategy, suggesting that the addition of objective parameters or subclassification reflecting physiologic or pathologic tests may be necessary for the targeted therapeutic approaches, particularly when therapeutic agents targeting novel mechanisms are available.

The Role of H2S in the Gastrointestinal Tract and Microbiota

The pathways and mechanisms of the production of H₂S in the gastrointestinal tract are briefly described, including endogenous H₂S produced by the organism and H₂S from microorganisms in the gastrointestinal tract. In addition, the physiological regulatory functions of H₂S on gastrointestinal motility, sensation, secretion and absorption, endocrine system, proliferation and differentiation of stem cells, and the possible mechanisms involved are introduced. In view of the complexity of biosynthesis, physiological roles, and the mechanism of H₂S, this chapter focuses on the interactions and dynamic balance among H₂S, gastrointestinal microorganisms, and the host. Finally, we focus on some clinical gastrointestinal diseases, such as inflammatory bowel disease, colorectal cancer, functional gastrointestinal disease, which might occur or develop when the above balance is broken. Pharmacological regulation of H₂S or the intestinal microorganisms related to H₂S might provide new therapeutic approaches for some gastrointestinal diseases.

Role of smoking in functional dyspepsia and irritable bowel syndrome: three random population-based studies

BACKGROUND

It is uncertain if functional dyspepsia (FD) or irritable bowel syndrome (IBS) are linked to smoking, and smoking cessation is not part of the routine advice provided to these patients.

AIM

To assess if smoking is an independent risk factor for FD and IBS.

METHODS

Three population-based endoscopy studies in Sweden with 2560 community individuals in total (mean age 51.5 years, 46% male). IBS (14.9%), FD (33.5%), and associated symptoms were assessed using the validated abdominal symptom questionnaire, and smoking (17.9%) was obtained from standardised questions during a clinic visit. The effect of smoking on symptom status was analysed in an individual person data meta-analysis using mixed effect logistic regression, adjusted for snuffing, age and sex.

RESULTS

Individuals smoking cigarettes reported significantly higher odds of postprandial distress syndrome (FD-PDS) (OR 10-19 cig/day = 1.42, 95% CI 1.04-1.98 P = 0.027, OR ≥20 cig/day = 2.16, 95% CI 1.38-3.38, P = 0.001) but not epigastric pain. Individuals smoking 20 or more cigarettes per day reported significantly higher odds of IBS-diarrhoea (OR = 2.40, 95% CI 1.12-5.16, P = 0.025), diarrhoea (OR = 2.01, 95%CI 1.28-3.16, P = 0.003), urgency (OR = 2.21, 95%CI 1.41-3.47, P = 0.001) and flatus (OR = 1.77, 95%CI 1.14-2.76, P = 0.012) than non-smokers. Smoking was not associated with IBS-constipation or IBS-mixed.

CONCLUSION

Smoking is an important environmental risk factor for postprandial distress syndrome, the most common FD subgroup, with over a twofold increased odds of PDS in heavy smokers. The role of smoking in IBS-diarrhoea, but not constipation, is also likely important.

United European Gastroenterology (UEG) and European Society for Neurogastroenterology and Motility (ESNM) consensus on functional dyspepsia

Background

Functional dyspepsia (FD) is one of the most common conditions in clinical practice. In spite of its prevalence, FD is associated with major uncertainties in terms of its definition, underlying pathophysiology, diagnosis, treatment, and prognosis.

Methods

A Delphi consensus was initiated with 41 experts from 22 European countries who conducted a literature summary and voting process on 87 statements. Quality of evidence was evaluated using the grading of recommendations, assessment, development, and evaluation (GRADE) criteria. Consensus (defined as >80% agreement) was reached for 36 statements.

Results

The panel agreed with the definition in terms of its cardinal symptoms (early satiation, postprandial fullness, epigastric pain, and epigastric burning), its subdivision into epigastric pain syndrome and postprandial distress syndrome, and the presence of accessory symptoms (upper abdominal bloating, nausea, belching), and overlapping conditions. Also, well accepted are the female predominance of FD, its impact on quality of life and health costs, and acute gastrointestinal infections, and anxiety as risk factors. In terms of pathophysiological mechanisms, the consensus supports a role for impaired gastric accommodation, delayed gastric emptying, hypersensitivity to gastric distention, Helicobacter pylori infection, and altered central processing of signals from the gastroduodenal region. There is consensus that endoscopy is mandatory for establishing a firm diagnosis of FD, but that in primary care, patients without alarm symptoms or risk factors can be managed without endoscopy. There is consensus that H. pylori status should be determined in every patient with dyspeptic symptoms and H. pylori positive patients should receive eradication therapy. Also, proton pump inhibitor therapy is considered an effective therapy for FD, but no other treatment approach reached a consensus. The long‐term prognosis and life expectancy are favorable.

Conclusions and Inferences

A multinational group of European experts summarized the current state of consensus on the definition, diagnosis and management of FD.

Current knowledge

Functional dyspepsia is one of the most common conditions encountered in clinical practice.

There is a lack of guidance for clinicians in guiding diagnosis and treatment of this prevalent condition.

No treatments are currently approved for the treatment of functional dyspepsia in Europe.

What is new here

A Delphi panel consisting of 41 experts from 22 European countries established the level of consensus on 87 statements regarding functional dyspepsia.

The statements reaching consensus serve to guide clinicians in recognizing, diagnosing and treating FD in clinical practice.

Endoscopy is mandatory for establishing a firm diagnosis of functional dyspepsia D, but in primary care patients without alarm symptoms or risk factors can be managed without endoscopy.

Helicobacter pylori status should be determined in every patient with dyspeptic symptoms and H. Pylori positive patients should receive eradication therapy.

Proton pump inhibitor‐therapy is considered an effective therapy for FD, but no other treatment approach reached consensus support.

Small Intestinal Bacterial Overgrowth in Functional Dyspepsia: A Systematic Review and Meta-Analysis

INTRODUCTION

This systematic review and meta-analysis aimed to determine the role of small intestinal bacterial overgrowth (SIBO) in patients with functional dyspepsia (FD).

METHODS

Electronic databases were searched until July 2020 for studies reporting prevalence of SIBO in FD. The prevalence rates, odds ratio, and 95% confidence intervals (CIs) of SIBO in FD and controls were calculated.

RESULTS

Seven studies with 263 patients with FD and 84 controls were identified. The odds for SIBO in patients with FD were significantly higher as compared to that in controls (odds ratio = 4.3, 95% CI, 1.1-17.5, 4 studies, 234 participants); however, there was moderate heterogeneity in this analysis. Including high-quality, case-control studies (all using glucose breath tests [GBTs]), the risk of SIBO in patients with FD as compared to controls was 2.8 higher (95% CI 0.8-10.0, 3 studies, 200 participants) with minimal heterogeneity in this analysis. Using the lactulose breath test, SIBO prevalence in FD was significantly higher (53.4%, 95% CI 33.9-71.9, 3 studies, 110 participants) as compared to that with GBT (17.2%, 95% CI 8.6-31.6, 4 studies, 153 participants). Substantial heterogeneity was found in studies using the lactulose breath test but not in studies using GBT. There was no significant difference in SIBO prevalence in patients with FD according to FD subtype.

DISCUSSION

This meta-analysis suggests a link between FD and SIBO. The quality of evidence is low and can be largely attributed to the type of breath test for SIBO diagnosis and clinical heterogeneity. More appropriately designed studies are required to confirm the link between SIBO and FD.