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

The effect of corticotropin-release hormone on duodenal permeability and immune activation in healthy volunteers in a double-blind placebo-controlled study

In functional dyspepsia, increased gut permeability, low-grade inflammation, and altered sensorimotor function have been reported. Both stress and corticotropin-release hormone (CRH) have been shown to increase small bowel permeability in a mast-cell-dependent manner. Moreover, eosinophil-derived CRH has been implicated in mast cell activation. The aim of this study was to evaluate whether CRH administration alters duodenal permeability and immune activation in healthy volunteers (HVs). An intravenous bolus of 100-µg CRH or placebo was administered in HVs in a crossover, double-blind, randomized manner. Two hours later, a gastroscopy was performed to measure permeability in Ussing chambers and to count mast cells and eosinophils on duodenal biopsies. Supernatant was assessed for eosinophil-derived neurotoxin (EDN), tryptase, and chymase. In addition, CRH was administrated ex vivo to baseline biopsies pretreated with or without lodoxamide. Results are described as means ± SD. P values < 0.05 were considered significant. Twenty HVs completed the study. Mast cell or eosinophil counts were not significantly altered after CRH versus Placebo (respectively P = 0.31 and P = 0.069). Tryptase, but not chymase, significantly decreased after CRH (respectively P = 0.037 and P = 0.44) with a trend for a decrease in EDN (P = 0.053). Permeability was unaltered comparing both conditions. Ex vivo, transepithelial electrical resistance significantly decreased after CRH exposure compared with baseline (P = 0.010), which was not prevented by pretreatment with lodoxamide. In vivo CRH administration reduced tryptase levels in the supernatant of duodenal biopsies without affecting permeability, whereas ex vivo duodenal permeability increased regardless of mast cell stabilization. These results suggest the involvement of mast cells in regulating gut permeability in HVs in response to CRH, possibly influenced by in vivo compensatory mechanisms.NEW & NOTEWORTHY Our investigation breaks new ground by directly examining the effects of corticotropin-release hormone (CRH) on duodenal alterations, including permeability and immune activation, in healthy subjects. Intriguingly, our findings highlight disparities between ex vivo and in vivo pathways affecting duodenal permeability, offering novel insights into the potential pathophysiology of CRH on the duodenum.

Management of Refractory Functional Gastrointestinal Disorders: What Role Should Psychiatrists Have?

Currently, it has been stated that psychiatric and psychological problems are equally paramount aspects of the clinical modulation and manifestation of both the central nervous and digestive systems, which could be used to restore balance. The present narrative review aims to provide an elaborate description of the bio-psycho-social facets of refractory functional gastrointestinal disorders, psychiatrists' role, specific psychiatric approach, and the latest psychiatric and psychological perspectives on practical therapeutic management. In this respect, "psyche," "psychiatry," "psychology," "psychiatrist," "psychotropic," and "refractory functional gastrointestinal disorders" (as the keywords) were searched in relevant English publications from January 1, 1950, to March 1, 2024, in the PubMed, Web of Science, Scopus, EMBASE, Cochrane Library, and Google Scholar databases. Eventually, the narrative technique was adopted to reach a compelling story with a high level of cohesion through material synthesis. The current literature recognizes the brain-gut axis modulation as a therapeutic target for refractory functional gastrointestinal disorders and the bio-psycho-social model as an integrated framework to explain disease pathogenesis. The results also reveal some evidence to affirm the benefits of psychotropic medications and psychological therapies in refractory functional gastrointestinal disorders, even when psychiatric symptoms were absent. It seems that psychiatrists are required to pay higher levels of attention to both the assessment and treatment of patients with refractory functional gastrointestinal disorders, accompanied by educating and training practitioners who take care of these patients.

Weichang' an pill alleviates functional dyspepsia through modulating brain-gut peptides and gut microbiota

OBJECTIVE

To evaluate the effect of Weichang'an pill (, WCAP) on functional dyspepsia (FD) and explore its regulation of brain-gut peptides (BGPs) and gut microbiota balance as a potential treatment mechanism.

METHODS

The "0 ℃ saline gavage + irregular feeding and tail clamp" method was used to establish the FD rat model, excluding the normal group. The successfully established FD rat models were randomly divided into the model group and the WCAP1 (WC1), WCAP2 (WC2), WCAP3 (WC3), WCAP4 (WC4), WCAP5 (WC5), and Domperidone (Dom) groups (n = 10 per group). The unhandled rats were designated as the control group. The gastrointestinal motility of the rats was evaluated using the charcoal propulsion test. Histopathology was assessed by hematoxylin and eosin (HE) staining. The enzyme-linked immunosorbnent assay method was used to detect the levels of motilin (MTL), gastrin (GAS), vasoactive intestinal peptide (VIP), and somatostatin (SS) in the serum from each group. In addition, the gut microbiota composition of fecal samples was analyzed using 16S rRNA sequencing.

RESULTS

Rat models were successfully established according to data from rat state, gastrointestinal motility assessments, and HE staining. WCAP improved FD symptoms by accelerating the gastric emptying and small intestinal transit of FD rats. Mechanistically, WCAP increased the levels of GAS and MTL and reduced the levels of VIP and SS. Moreover, WCAP treatment restored the total relative abundance of Firmicutes and Bacteroidetes, increased the species richness of the gut flora, and modulated the changes in the composition and function of the gut microbiota.

CONCLUSION

WCAP can effectively promote the recovery of gastrointestinal motility disorders in FD rats. The mechanism may be related to regulating the secretion of BGPs and the composition of the gut microbiota.

Progress in the mechanism of functional dyspepsia: roles of mitochondrial autophagy in duodenal abnormalities

Mitochondria are the main source of energy for cellular activity. Their functional damage or deficiency leads to cellular deterioration, which in turn triggers autophagic reactions. Taking mitochondrial autophagy as a starting point, the present review explored the mechanisms of duodenal abnormalities in detail, including mucosal barrier damage, release of inflammatory factors, and disruption of intracellular signal transduction. We summarized the key roles of mitochondrial autophagy in the abnormal development of the duodenum and examined the in-depth physiological and pathological mechanisms involved, providing a comprehensive theoretical basis for understanding the pathogenesis of functional dyspepsia. At present, it has been confirmed that an increase in the eosinophil count and mast cell degranulation in the duodenum can trigger visceral hypersensitive reactions and cause gastrointestinal motility disorders. In the future, it is necessary to continue exploring the molecular mechanisms and signaling pathways of mitochondrial autophagy in duodenal abnormalities. A deeper understanding of mitochondrial autophagy provides important references for developing treatment strategies for functional dyspepsia, thereby improving clinical efficacy and patient quality of life.

Current opinion: functional dyspepsia

PURPOSE OF REVIEW

Functional dyspepsia is a common gastrointestinal disease that is under-recognized and under-diagnosed. It is a complex disorder of gut-brain interaction with no FDA-approved treatment options. The purpose of this review is to highlight updates in the proposed pathophysiology and present new data regarding potential therapies for functional dyspepsia.

RECENT FINDINGS

Alterations in the intestinal microbiome and integrity of the intestinal membrane may play a crucial role in the pathogenesis of functional dyspepsia. The low FODMAP diet, in addition to modulating the microbiome with antibiotics and probiotics, are targets for large future studies. Novel methods of delivery of gut-brain therapies have shown promising results, especially virtual reality.

SUMMARY

The pathophysiology and management of functional dyspepsia is complex and there is still much unknown; however, continued research is identifying new targets for treatment. New and more targeted treatment options provide clinicians a variety of tools to offer patients with functional dyspepsia.

From gut to brain: unveiling probiotic effects through a neuroimaging perspective-A systematic review of randomized controlled trials

The gut-brain axis, a bidirectional communication network between the gastrointestinal system and the brain, significantly influences mental health and behavior. Probiotics, live microorganisms conferring health benefits, have garnered attention for their potential to modulate this axis. However, their effects on brain function through gut microbiota modulation remain controversial. This systematic review examines the effects of probiotics on brain activity and functioning, focusing on randomized controlled trials using both resting-state and task-based functional magnetic resonance imaging (fMRI) methodologies. Studies investigating probiotic effects on brain activity in healthy individuals and clinical populations (i.e., major depressive disorder and irritable bowel syndrome) were identified. In healthy individuals, task-based fMRI studies indicated that probiotics modulate brain activity related to emotional regulation and cognitive processing, particularly in high-order areas such as the amygdala, precuneus, and orbitofrontal cortex. Resting-state fMRI studies revealed changes in connectivity patterns, such as increased activation in the Salience Network and reduced activity in the Default Mode Network. In clinical populations, task-based fMRI studies showed that probiotics could normalize brain function in patients with major depressive disorder and irritable bowel syndrome. Resting-state fMRI studies further suggested improved connectivity in mood-regulating networks, specifically in the subcallosal cortex, amygdala and hippocampus. Despite promising findings, methodological variability and limited sample sizes emphasize the need for rigorous, longitudinal research to clarify the beneficial effects of probiotics on the gut-brain axis and mental health.

Comparison of the effects of Amomum tsaoko and its adulterants on functional dyspepsia rats based on metabolomics analysis

Amomum tsaoko (AT) is commonly used in clinical practice to treat abdominal distension and pain. It is also a seasoning for cooking, with the functions of appetizing, invigorating the spleen, and being digestive-promoting. Amomum tsaoko (AT) has three adulterants, Amomum paratsaoko (AP), Amomum koenigii (AK), and Alpinia katsumadai Hayata, because of the confusion in historical classics regarding recorded sources as well as the near geographic distribution and fruit morphological similarities. In this study, we established a functional dyspepsia (FD) rat model and then treated it with the corresponding medicinal solutions AT, AP, AK, and AKH. The gastric emptying rate, intestinal propulsion rate, serum biochemical indicators, histopathological changes, and fecal metabolism were measured. The efficacy and mechanism of AT, AP, AK, and AKH in the treatment of FD were compared. Fecal metabolomics revealed that 20 potential biomarkers were involved in seven significant metabolic pathways in FD rats. These pathways include ubiquinone and other terpenoid-quinone biosynthesis, glycerophospholipid metabolism, tyrosine metabolism, primary bile acid biosynthesis, purine metabolism, folate biosynthesis, and amino sugar and nucleotide sugar metabolism. AP regulates 6 metabolic pathways, 5 metabolic pathways affected by AT, 4 metabolic pathways affected by AK, and 2 metabolic pathways affected by AKH.The above results suggest that the different effects of AT, AP, AK, and AKH on FD rats may be due to their different regulatory effects on the metabolome.

Duodenal microbiota dysbiosis in functional dyspepsia and its potential role of the duodenal microbiota in gut-brain axis interaction: a systematic review

Background and aims

Functional dyspepsia (FD) is a common gastrointestinal disorder associated with brain-gut interaction disturbances. In recent years, accumulating evidence points to the duodenum as a key integrator in dyspepsia symptom generation. Investigations into the pathological changes in the duodenum of FD patients have begun to focus on the role of duodenal microbiota dysbiosis. This review summarizes duodenal microbiota changes in FD patients and explores their relationship with gut-brain interaction dysregulation.

Methods

Ten databases, including PubMed, MEDLINE, and the Cochrane Library, were searched from inception to 10th October 2023 for clinical interventional and observational studies comparing the duodenal microbiota of FD patients with controls. We extracted and qualitatively summarized the alpha diversity, beta diversity, microbiota composition, and dysbiosis-related factors.

Results

A total of nine studies, consisting of 391 FD patients and 132 non-FD controls, were included. The findings reveal that the alpha diversity of the duodenal microbiota in FD patients does not exhibit a significant difference compared to non-FD controls, although an upward trend is observed. Furthermore, alterations in the duodenal microbiota of FD patients are associated with the symptom burden, which, in turn, impacts their quality of life. In FD patients, a considerable number of duodenal microbiota demonstrate a marked ascending trend in relative abundance, including taxa such as the phylum Fusobacteria, the genera Alloprevotella, Corynebacterium, Peptostreptococcus, Staphylococcus, Clostridium, and Streptococcus. A more pronounced declining trend is observed in the populations of the genera Actinomyces, Gemella, Haemophilus, Megasphaera, Mogibacterium, and Selenomonas within FD patients. A negative correlation in the relative abundance changes between Streptococcus and Prevotella is identified, which correlates with the severity of symptom burden in FD patients. Moreover, the alterations in specific microbial communities in FD patients and their potential interactions with the gut-brain axis merit significant attention.

Conclusion

Microbial dysbiosis in FD patients is linked to the onset and exacerbation of symptoms and is related to the disorder of gut-brain interaction. Larger-scale, higher-quality studies, along with comprehensive meta-omics research, are essential to further elucidate the characteristics of the duodenal microbiota in FD patients and its role in FD pathogenesis.Systematic review registration: CRD42023470279, URL: https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42023470279.

Gut microbiota and functional dyspepsia: a two-sample Mendelian randomization study

Background

Numerous studies have established that alterations in the gut microbiota (GM) constitute an embedded mechanism in functional dyspepsia (FD). However, the specific GM taxa implicated in the pathological process of FD have remained unclear.

Methods

A two-sample Mendelian randomization analysis was initially conducted to examine the causal relationships between GM and FD, utilizing GWAS data from the MiBioGen Consortium (18,340 cases) and FinnGenn (8,875 cases vs. 320,387 controls). The MR study primarily employed the inverse-variance weighted (IVW) method. Sensitivity analyses were performed to test for heterogeneity and pleiotropy. Single-nucleotide polymorphisms of causal GM taxa were mapped to genes, which were subsequently assessed for causal relationships with FD employing the same methodology.

Results

IVW results revealed that the genus Clostridium innocuum group (OR: 1.12, 95% CI: 1.02-1.24, P = 0.020) and genus Ruminiclostridium 9 were positively associated with FD risk (OR: 1.27, 95% CI: 1.03-1.57, P = 0.028), while the genus Lachnospiraceae FCS020 group tended to exert a negative effect on FD risk (OR = 0.84, 95% CI: 0.73-0.98, P = 0.023). Among GM-related genes, a notable association was observed between RSRC1 and increased FD risk (OR = 1.13, 95% CI: 1.07-1.20, P < 0.001). In sensitivity analyses, no significant pleiotropy or heterogeneity of the results was found.

Conclusions

This study furnished evidence for distinct effects of specific GM taxa on FD risk and hinted at a potential biological mechanism, thereby offering theoretical underpinning for future microbiotherapy of FD.

The Association between Functional Dyspepsia and Metabolic Syndrome-The State of the Art

Functional dyspepsia is a common functional disorder of the gastrointestinal tract that is responsible for many primary care visits. No organic changes have been found to explain its symptoms. We hypothesize that modern lifestyles and environmental factors, especially psychological stress, play a crucial role in the high prevalence of functional dyspepsia and metabolic syndrome. While gastrointestinal tract diseases are rarely linked to metabolic disorders, chronic stress, obesity-related metabolic syndrome, chronic inflammation, intestinal dysbiosis, and functional dyspepsia have significant pathophysiological associations. Functional dyspepsia, often associated with anxiety and chronic psychological stress, can activate the neuroendocrine stress axis and immune system, leading to unhealthy habits that contribute to obesity. Additionally, intestinal dysbiosis, which is commonly present in functional dyspepsia, can exacerbate systemic inflammation and obesity, further promoting metabolic syndrome-related disorders. It is worth noting that the reverse is also true: obesity-related metabolic syndrome can worsen functional dyspepsia and its associated symptoms by triggering systemic inflammation and intestinal dysbiosis, as well as negative emotions (depression) through the brain-gut axis. To understand the pathophysiology and deliver an effective treatment strategy for these two difficult-to-cure disorders, which are challenging for both caregivers and patients, a psychosocial paradigm is essential.

Research Progress for Probiotics Regulating Intestinal Flora to Improve Functional Dyspepsia: A Review

Functional dyspepsia (FD) is a common functional gastrointestinal disorder. The pathophysiology remains poorly understood; however, alterations in the small intestinal microbiome have been observed. Current treatments for FD with drugs are limited, and there are certain safety problems. A class of active probiotic bacteria can control gastrointestinal homeostasis, nutritional digestion and absorption, and the energy balance when taken in certain dosages. Probiotics play many roles in maintaining intestinal microecological balance, improving the intestinal barrier function, and regulating the immune response. The presence and composition of intestinal microorganisms play a vital role in the onset and progression of FD and serve as a critical factor for both regulation and potential intervention regarding the management of this condition. Thus, there are potential advantages to alleviating FD by regulating the intestinal flora using probiotics, targeting intestinal microorganisms. This review summarizes the research progress of probiotics regarding improving FD by regulating intestinal flora and provides a reference basis for probiotics to improve FD.

Targeting the gut-microbiota-brain axis in irritable bowel disease to improve cognitive function - recent knowledge and emerging therapeutic opportunities

The brain-gut axis forms a bidirectional communication system between the gastrointestinal (GI) tract and cognitive brain areas. Disturbances to this system in disease states such as inflammatory bowel disease have consequences for neuronal activity and subsequent cognitive function. The gut-microbiota-brain axis refers to the communication between gut-resident bacteria and the brain. This circuits exists to detect gut microorganisms and relay information to specific areas of the central nervous system (CNS) that in turn, regulate gut physiology. Changes in both the stability and diversity of the gut microbiota have been implicated in several neuronal disorders, including depression, autism spectrum disorder Parkinson's disease, Alzheimer's disease and multiple sclerosis. Correcting this imbalance with medicinal herbs, the metabolic products of dysregulated bacteria and probiotics have shown hope for the treatment of these neuronal disorders. In this review, we focus on recent advances in our understanding of the intricate connections between the gut-microbiota and the brain. We discuss the contribution of gut microbiota to neuronal disorders and the tangible links between diseases of the GI tract with cognitive function and behaviour. In this regard, we focus on irritable bowel syndrome (IBS) given its strong links to brain function and anxiety disorders. This adds to the growing body of evidence supporting targeted therapeutic strategies to modulate the gut microbiota for the treatment of brain/mental-health-related disease.

Efficacy of faecal microbiota transplantation in patients with progressive supranuclear palsy-Richardson's syndrome: a phase 2, single centre, randomised clinical trial

Background

Faecal microbiota transplantation (FMT) has demonstrated efficacy in treating gastrointestinal (GI) diseases, such as Clostridium difficile infection (CDI) and inflammatory bowel disease (IBD). GI dysfunction is a frequent and occasionally dominating symptom of progressive supranuclear palsy-Richardson's syndrome (PSP-RS). However, it is not known whether FMT has clinical efficacy for PSP-RS.

Methods

This 36-week, randomised, placebo-controlled, parallel-group, phase 2 clinical trial was performed at a university tertiary referral hospital in China. From August 15 2021 to December 31 2021, a total of 68 newly diagnosed patients with PSP-RS (male 40 [59%], female 28 [41%]) who had never received any antiparkinsonian medications were enrolled and randomly assigned to receive either healthy donor FMT (n = 34, FMT group) or a mixture of 0.9% saline and food colouring (E150c) as sham transplantation (n = 34, placebo group) through transendoscopic enteral tubing (TET). Two days after oral antibiotics, participants received 1 week of transplantation. After an interval of 4 weeks, retransplantation was performed. Then, the last transplantation was given after another interval of 4 weeks, and the participants were followed up for 24 weeks (week 36). Clinicaltrials.gov identifier: ChiCTR-2100045397.

Findings

Among 68 patients who were randomised (mean age, 67.2 (SD 5.1); 40 [59%] were male, 28 [41%] were female), 63 participants completed the trial. Efficacy analyses were performed on the intention-to-treat (ITT) analysis set. At week 16, the mean PSP Rating Scale (PSPRS) scores (the primary outcome) improved from 40.1 (SD 7.6) to 36.9 (SD 5.9) in the FMT group, whereas the scores changed from 40.1 (SD 6.9) to 41.7 (SD 6.2) in the placebo group, for a treatment benefit of 4.3 (95% CI, 3.2-5.4) (P < 0.0001). After 3-cycle intervention, symptoms of constipation, depression, and anxiety (the secondary outcome) improved significantly at week 16 in the FMT group compared with the placebo group, the majority of which were maintained at the 24-week follow-up (week 36).

Interpretation

Our findings suggest that, compared with placebo, FMT treatment significantly improved motor and nonmotor symptoms in patients with PSP-RS, as well as reduced intestinal inflammation and enhanced the intestinal barrier by regulating the intestinal microbiota composition.

Funding

The National Natural Science Foundation of China (No. 82122022, 82171248, 81873791, and 82230084), Natural Science Foundation of Henan Province for Excellent Young Scholars (no. 202300410357), and Henan Province Young and Middle-Aged Health Science and Technology Innovation Talent Project (YXKC2020033).

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.