Feeling down? A systematic review of the gut microbiota in anxiety/depression and irritable bowel syndrome

Discrete interplay of gut microbiota L-tryptophan metabolites in host biology and disease

The gut microbiota and the host maintain a conjoint relationship and together achieve optimal physiology via a multitude of interactive signalling cues. Dietary-derived L-tryptophan (L-trp) is enzymatically metabolized by the resident symbiotic gut microbiota to indole and various indole derivatives. Indole and indole metabolites secreted by the gut bacteria act locally in the intestinal cells as well as distally and modulate tissue-specific functions which are beneficial to the host. Functions attributed to these microbial indole metabolites in the host include regulation of intestinal permeability, immunity and mucosal roles, inflammation, and insulin sensitivity. On the other hand, dysregulation of gut microbiota L-trp metabolism compromises the optimal availability of indole and indole metabolites and can induce the onset of metabolic disorders, inflammation, liver steatosis, and decrease gut barrier integrity. Gut dysbiosis is regarded as one of the prime reasons for this deregulated microbial-derived indole metabolites. A number of indole metabolites from the gut bacteria have been identified recently displaying variable affinity towards xenobiotic nuclear receptors. Microbial metabolite mimicry concept can be used to design and develop novel indole-moiety-containing compounds with higher affinity towards the receptors and efficacy in preclinical studies. Such compounds may serve as therapeutic drugs in clinical trials in the future. In this article, I review L-trp metabolism in the host and gut microbiota and the various physiological functions, patho-physiologies associated with the microbial-released indole metabolites in the host, including the metabolite mimicry-based concept to develop tailored indole-containing novel experimental drugs.

Tannic acid protects against colitis by regulating the IL17 - NFκB and microbiota - methylation pathways

Tannic acid, a bioactive polyphenol found in various phytogenic foods and medicinal plants, has potential prevention effects on colitis, though more evidence and mechanistic studies are required to substantiate this. In this study, we investigated the effects of different doses from 0 to 3 mg/mL of tannic acid on mice, ultimately selecting a dose of 3 mg/mL for the anti-colitis trial based on growth and intestinal morphology assessments. Using the DSS-induced colitis model, we found that tannic acid may alleviate colitis by inhibiting the IL-17 - NF-κB p65 signaling pathway and modulating epigenetic pathways, particularly methylation modifications. Additionally, tannic acid altered the gut microbiota, increasing the abundances of Prevotella, Eubacterium_siraeum_group, and Enterorhabdus in the colon. Supplementation with Eubacterium siraeum via gavage also inhibited colitis, accompanied by increased folate and methylation regulators in the colon. These findings suggest that tannic acid may inhibit colitis through the suppression of the IL-17 - NF-κB pathway and the enhancement of microbiota-mediated methylation pathways.

A meta-analysis of randomized controlled trials evaluating the effectiveness of fecal microbiota transplantation for patients with irritable bowel syndrome

OBJECTIVE

Multiple randomized controlled trials (RCTs) have investigated the efficacy of fecal microbiota transplantation (FMT) for irritable bowel syndrome (IBS), but have yielded inconsistent results. We updated the short-term and long-term efficacy of FMT in treating IBS, and performed a first-of-its-kind exploration of the relationship between gut microbiota and emotions.

METHODS

We conducted a comprehensive search of PubMed, Embase, Web of Science, and the Cochrane Library using various search strategies to identify all eligible studies. The inclusion criteria for data extraction were randomized controlled trials (RCTs) that investigated the efficacy of fecal microbiota transplantation (FMT) compared to placebo in adult patients (≥ 18 years old) with irritable bowel syndrome (IBS). A meta-analysis was then performed to assess the summary relative risk (RR) and corresponding 95% confidence intervals (CIs).

RESULTS

Out of 3,065 potentially relevant records, a total of 10 randomized controlled trials (RCTs) involving 573 subjects met the eligibility criteria for inclusion in the meta-analysis. The meta-analyses revealed no significant differences in short-term (12 weeks) (RR 0.20, 95% CI -0.04 to 0.44), long-term (52 weeks) global improvement (RR 1.38, 95% CI 0.87 to 2.21), besides short-term (12 weeks) (SMD - 48.16, 95% CI -102.13 to 5.81, I2 = 90%) and long-term (24 weeks) (SMD 2.16, 95% CI -60.52 to 64.83, I2 = 68%) IBS-SSS. There was statistically significant difference in short-term improvement of IBS-QoL (SMD 10.11, 95% CI 0.71 to 19.51, I2 = 82%), although there was a high risk of bias. In terms of long-term improvement (24 weeks and 54 weeks), there were no significant differences between the FMT and placebo groups (SMD 7.56, 95% CI 1.60 to 13.52, I2 = 0%; SMD 6.62, 95% CI -0.85 to 14.08, I2 = 0%). Sensitivity analysis indicated that there were visible significant effects observed when the criteria were based on Rome IV criteria (RR 16.48, 95% CI 7.22 to 37.62) and Gastroscopy (RR 3.25, 95%CI 2.37 to 4.47), Colonoscopy (RR 1.42, 95% CI 0.98 to 2.05). when using mixed stool FMT based on data from two RCTs, no significant difference was observed (RR 0.94, 95% CI 0.66 to -1.34). The remission of depression exhibited no significant difference between the FMT and placebo groups at the 12-week mark (SMD - 0.26, 95% CI -3.09 to 2.58), and at 24 weeks (SMD - 2.26, 95% CI -12.96 to 8.45). Furthermore, major adverse events associated with FMT were transient and self-limiting.

DISCUSSION

Based on the available randomized controlled trials (RCTs), the current evidence does not support the efficacy of FMT in improving global IBS symptoms in the long term. The differential results observed in subgroup analyses raise questions about the accurate identification of suitable populations for FMT. Further investigation is needed to better understand the reasons behind these inconsistent findings and to determine the true potential of FMT as a treatment for IBS.

Co-decoction of Lilii bulbus and Radix Rehmannia Recens and its key bioactive ingredient verbascoside inhibit neuroinflammation and intestinal permeability associated with chronic stress-induced depression via the gut microbiota-brain axis

BACKGROUND

Gut microbiota plays a critical role in the pathogenesis of depression and are a therapeutic target via maintaining the homeostasis of the host through the gut microbiota-brain axis (GMBA). A co-decoction of Lilii bulbus and Radix Rehmannia Recens (LBRD), in which verbascoside is the key active ingredient, improves brain and gastrointestinal function in patients with depression. However, in depression treatment using verbascoside or LBRD, mechanisms underlying the bidirectional communication between the intestine and brain via the GMBA are still unclear.

PURPOSE

This study aimed to examine the role of verbascoside in alleviating depression via gut-brain bidirectional communication and to study the possible pathways involved in the GMBA.

METHODS

Key molecules and compounds involved in antidepressant action were identified using HPLC and transcriptomic analyses. The antidepressant effects of LBRD and verbascoside were observed in chronic stress induced depression model by behavioural test, neuronal morphology, and synaptic dendrite ultrastructure, and their neuroprotective function was measured in corticosterone (CORT)-stimulated nerve cell injury model. The causal link between the gut microbiota and the LBRD and verbascoside antidepressant efficacy was evaluate via gut microbiota composition analysis and faecal microbiota transplantation (FMT).

RESULTS

LBRD and Verbascoside administration ameliorated depression-like behaviours and synaptic damage by reversing gut microbiota disturbance and inhibiting inflammatory responses as the result of impaired intestinal permeability or blood-brain barrier leakiness. Furthermore, verbascoside exerted neuroprotective effects against CORT-induced cytotoxicity in an in vitro depression model. FMT therapy indicated that verbascoside treatment attenuated gut inflammation and central nervous system inflammatory responses, as well as eliminated neurotransmitter and brain-gut peptide deficiencies in the prefrontal cortex by modulating the composition of gut microbiota. Lactobacillus, Parabacteroides, Bifidobacterium, and Ruminococcus might play key roles in the antidepressant effects of LBRD via the GMBA.

CONCLUSION

The current study elucidates the multi-component, multi-target, and multi-pathway therapeutic effects of LBRD on depression by remodeling GMBA homeostasis and further verifies the causality between gut microbiota and the antidepressant effects of verbascoside and LBRD.

Human microbiota from drug-naive patients with obsessive-compulsive disorder drives behavioral symptoms and neuroinflammation via succinic acid in mice

Emerging evidence suggests that the gut microbiota is closely related to psychiatric disorders. However, little is known about the role of the gut microbiota in the development of obsessive-compulsive disorder (OCD). Here, to investigate the contribution of gut microbiota to the pathogenesis of OCD, we transplanted fecal microbiota from first-episode, drug-naive OCD patients or demographically matched healthy individuals into antibiotic-treated specific pathogen-free (SPF) mice and showed that colonization with OCD microbiota is sufficient to induce core behavioral deficits, including abnormal anxiety-like and compulsive-like behaviors. The fecal microbiota was analyzed using 16 S rRNA full-length sequencing, and the results demonstrated a clear separation of the fecal microbiota of mice colonized with OCD and control microbiota. Notably, microbiota from OCD-colonized mice resulted in injured neuronal morphology and function in the mPFC, with inflammation in the mPFC and colon. Unbiased metabolomic analyses of the serum and mPFC region revealed the accumulation of succinic acid (SA) in OCD-colonized mice. SA impeded neuronal activity and induced an inflammatory response in both the colon and mPFC, impacting intestinal permeability and brain function, which act as vital signal mediators in gut microbiota-brain-immune crosstalk. Manipulations of dimethyl malonate (DM) have been reported to exert neuroprotective effects by suppressing the oxidation of accumulated succinic acid, attenuating the downstream inflammatory response and neuronal damage, and can help to partly improve abnormal behavior and reduce neuroinflammation and intestinal inflammation in OCD-colonized mice. We propose that the gut microbiota likely regulates brain function and behaviors in mice via succinic acid signaling, which contributes to the pathophysiology of OCD through gut-brain crosstalk and may provide new insights into the treatment of this disorder.

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.

Unraveling the Role of the Blood-Brain Barrier in the Pathophysiology of Depression: Recent Advances and Future Perspectives

Depression is a highly prevalent psychological disorder characterized by persistent dysphoria, psychomotor retardation, insomnia, anhedonia, suicidal ideation, and a remarkable decrease in overall well-being. Despite the prevalence of accessible antidepressant therapies, many individuals do not achieve substantial improvement. Understanding the multifactorial pathophysiology and the heterogeneous nature of the disorder could lead the way toward better outcomes. Recent findings have elucidated the substantial impact of compromised blood-brain barrier (BBB) integrity on the manifestation of depression. BBB functions as an indispensable defense mechanism, tightly overseeing the transport of molecules from the periphery to preserve the integrity of the brain parenchyma. The dysfunction of the BBB has been implicated in a multitude of neurological disorders, and its disruption and consequent brain alterations could potentially serve as important factors in the pathogenesis and progression of depression. In this review, we extensively examine the pathophysiological relevance of the BBB and delve into the specific modifications of its components that underlie the complexities of depression. A particular focus has been placed on examining the effects of peripheral inflammation on the BBB in depression and elucidating the intricate interactions between the gut, BBB, and brain. Furthermore, this review encompasses significant updates on the assessment of BBB integrity and permeability, providing a comprehensive overview of the topic. Finally, we outline the therapeutic relevance and strategies based on BBB in depression, including COVID-19-associated BBB disruption and neuropsychiatric implications. Understanding the comprehensive pathogenic cascade of depression is crucial for shaping the trajectory of future research endeavors.

Risk factors for irritable bowel syndrome: A review

Irritable bowel syndrome (IBS) is one of the most common diseases of the digestive tract from the group of disorders of interaction in the gut-brain axis. IBS has a negative impact of on patients' quality of life and the significant social and economic burden of the disease due to the low effectiveness of available treatment strategies, which are only symptomatic, without impacting factors and mechanisms of intestinal dysfunction. From this perspective, it is critical to study the factors contributing to the onset and persistence of IBS symptoms to improve the early diagnosis of the disease and implement targeted prevention technology in at-risk groups. The objective of this paper is to systematize data on the main risk factors for IBS, including hereditary predisposition, stress and psycho-emotional state, diet and eating habits, and acute intestinal infections.

Cold exposure, gut microbiota and health implications: A narrative review

Temperature has been recognized as an important environmental factor affecting the composition and function of gut microbiota (GM). Although research on high-temperature impacts has been well studied, knowledge about the effect of cold exposure on GM remains limited. This narrative review aims to synthesize the latest scientific findings on the impact of cold exposure on mammalian GM, and its potential health implications. Chronic cold exposure could disrupt the α-diversity and the composition of GM in both experimental animals and wild-living hosts. Meanwhile, cold exposure could impact gut microbial metabolites, such as short-chain fatty acids. We also discussed plausible biological pathways and mechanisms by which cold-induced changes may impact host health, including metabolic homeostasis, fitness and thermogenesis, through the microbiota-gut-brain axis. Intriguingly, alterations in GM may provide a tool for favorably modulating the host response to the cold temperature. Finally, current challenges and future perspectives are discussed, emphasizing the need for translational research in humans. GM could be manipulated by utilizing nutritional strategies, such as probiotics and prebiotics, to deal with cold-related health issues and enhance well-being in populations living or working in cold environments.

Polycystic Ovary Syndrome and Irritable Bowel Syndrome: Is There a Common Pathway?

OBJECTIVE

Little is known about how polycystic ovary syndrome (PCOS) is linked to irritable bowel syndrome (IBS). This study aimed to review the existing literature regarding the association between PCOS or its symptoms and complications with IBS.

METHODS

In this review, studies that investigated the proposed cross-link between features of PCOS and IBS were included. This review collectively focused on recent findings on the mechanism and novel insight regarding the association between IBS and PCOS in future clinical practice. An electronic search of PubMed, Scopus, Epistemonikos, Cochrane Library and Google Scholar was performed. We did not restrict the study setting and publication date.

RESULTS

The existing evidence has not completely answered the question of whether there is an association between PCOS and IBS and vice versa. Six case-control studies (793 women with PCOS and 547 women in the control group) directly assessed the association between PCOS and IBS. The prevalence of IBS among women with PCOS in these studies has ranged from 10% to 52% compared with 5%-50% in control groups. Evidence suggested the common pathways may have contributed to the interaction between IBS and PCOS, including metabolic syndrome, sex hormone fluctuation, dysregulation of neurotransmitters, psychological problems and environmental and lifestyle factors. To date, it is still ambiguous which of the mentioned components largely contributes to the pathogenesis of both.

CONCLUSION

Although limited evidence has shown a higher prevalence of IBS in women with PCOS, there are several potential, direct and common indirect pathways contributing to the development of both IBS and PCOS.

Gut dysbiosis induces the development of depression-like behavior through abnormal synapse pruning in microglia-mediated by complement C3

BACKGROUND

Remodeling eubiosis of the gut microenvironment may contribute to preventing the occurrence and development of depression. Mounting experimental evidence has shown that complement C3 signaling is associated with the pathogenesis of depression, and disruption of the gut microbiota may be an underlying cause of complement system activation. However, the mechanism by which complement C3 participates in gut-brain crosstalk in the pathogenesis of depression remains unknown.

RESULTS

In the present study, we found that chronic unpredictable mild stress (CUMS)-induced mice exhibited obvious depression-like behavior as well as cognitive impairment, which was associated with significant gut dysbiosis, especially enrichment of Proteobacteria and elevation of microbiota-derived lipopolysaccharides (LPS). In addition, peripheral and central complement C3 activation and central C3/CR3-mediated aberrant synaptic pruning in microglia have also been observed. Transplantation of gut microbiota from CUMS-induced depression model mice into specific pathogen-free and germ-free mice induced depression-like behavior and concomitant cognitive impairment in the recipient mice, accompanied by increased activation of the complement C3/CR3 pathway in the prefrontal cortex and abnormalities in microglia-mediated synaptic pruning. Conversely, antidepressants and fecal microbiota transplantation from antidepressant-treated donors improved depression-like behaviors and restored gut microbiome disturbances in depressed mice. Concurrently, inhibition of the complement C3/CR3 pathway, amelioration of abnormal microglia-mediated synaptic pruning, and increased expression of the synapsin and postsynaptic density protein 95 were observed. Collectively, our results revealed that gut dysbiosis induces the development of depression-like behaviors through abnormal synapse pruning in microglia-mediated by complement C3, and the inhibition of abnormal synaptic pruning is the key to targeting microbes to treat depression.

CONCLUSIONS

Our findings provide novel insights into the involvement of complement C3/CR3 signaling and aberrant synaptic pruning of chemotactic microglia in gut-brain crosstalk in the pathogenesis of depression. Video Abstract.

Effects of aerobic exercise or Tai Chi Chuan interventions on problematic mobile phone use and the potential role of intestinal flora: A multi-arm randomized controlled trial

BACKGROUND

Problematic use of mobile phones (PMPU) has been described as a serious public health issue.

METHODS

This study was a parallel three-arm randomized controlled trial and has completed registration (ClinicalTrials.gov Identifier: NCT05843591). Ninety college students with PMPU were randomly assigned to the aerobic exercise group (AE group, n = 30), the Tai Chi Chuan group (TCC group, n = 30), or the wait-list control group (WLC group, n = 30). At the end of the intervention, stool samples from the study participants were collected for biological analysis based on 16 S rDNA amplicon sequencing technology. The primary outcome was addiction symptoms assessed by the Smartphone Addiction Scale-Short Version (SAS-SV). The secondary outcomes are emotional symptoms, physical symptoms, and flora species.

RESULTS

Compared with the WLC group, the AE and TCC groups showed reductions in PMPU levels, physical and mental fatigue, but there was no difference between the two groups. Moreover, the effect of increasing self-esteem embodied in the TCC group was not present in the AE group. Compared to the WLC group, the relative abundance of Bacteroidaceae and Bacteroides were lower in the AE group, while the relative abundance of Erysipelotrichaceae and Alistipes were lower in the TCC group. And the relative abundance of Bacteroidaceae, Bacteroides, and Alistipes were significantly and negatively correlated with the decline in PMPU scores.

CONCLUSION

AE or TCC is an effective, safe and efficient intervention for college students with PMPU, providing some physiological and psychological benefits and having some impact on their intestinal flora.

Association of major depressive disorder and increased risk of irritable bowel syndrome: A population-based cohort study and a two-sample Mendelian randomization study in the UK biobank

OBJECTIVE

To examine the association between depression and the risk of incident irritable bowel syndrome (IBS).

METHODS

We included 98,564 participants free of IBS in the UK biobank. Depression was defined by self-report and Hospital Episode Statistics. The main outcome was incident IBS. Cox proportional hazards regression models and two-sample mendelian randomization were performed to estimate the risk of incident IBS.

RESULTS

Among 98,564 participants, 8770 (8.9 %) participants had a depression diagnosis at baseline. During a median of 12.9-year follow-up, 224 cases of incident IBS were identified in patients with depression (2.0 per 1000 person-years), compared with 1625 cases in reference individuals (1.5 per 1000 person-years). After adjustment, the hazard ratio of incident IBS associated with depression was 1.26 (95 % CI: 1.01-1.41). Sensitivity analysis indicated similar results. The two-sample mendelian randomization based on the inverse variance weighted method provided evidence for the harmful role of depression in an increased risk of IBS with an OR of 1.57 (95 % CI: 1.24-1.99).

LIMITATIONS

Depression was mainly measured by self-report online CIDI-SF in the current study, rather than the gold diagnostic criteria including clinical structured interview, which might lead to potential measurement error. Lifestyle behaviors might change during the long-term follow-up, and time-varying covariates (i.e., smoking and alcohol status) may bias the estimate.

CONCLUSIONS

Depression is associated with an increased risk of incident IBS. Further studies are warranted to confirm the role of depression on incident IBS and elucidate the underlying mechanisms.

Efficacy of an eHealth self-management program in reducing irritable bowel syndrome symptom severity: a randomized controlled trial

This study aimed to verify whether an eHealth-based self-management program can reduce irritable bowel syndrome (IBS) symptom severity. An open-label simple randomized controlled trial was conducted that compared an intervention group (n = 21) participating in an eHealth self-management program, which involved studying IBS-related information from an established self-help guide followed by in-built quizzes, with a treatment-as-usual group (n = 19) that, except for pharmacotherapy, had no treatment restrictions. Participants were female Japanese university students. The eHealth group received unlimited access to the self-management program for 8 weeks on computers and mobile devices. The primary outcome, participants' severity of IBS symptoms assessed using the IBS-severity index (IBS-SI), and the secondary outcomes of participants' quality of life, gut bacteria, and electroencephalography alpha and beta power percentages were measured at baseline and 8 weeks. A significant difference was found in the net change in IBS-SI scores between the eHealth and treatment-as-usual groups, and the former had significantly lower IBS-SI scores following the 8-week intervention than at baseline. Moreover, there was a significant difference in the net change in phylum Cyanobacteria between the eHealth and treatment-as-usual groups. Thus, the eHealth-based self-management program successfully reduced the severity of IBS symptoms.

Cognitive function in patients with irritable bowel syndrome: impairment is common and only weakly correlated with depression/anxiety and severity of gastrointestinal symptoms

OBJECTIVE

To investigate cognitive function in patients with irritable bowel syndrome (IBS) and its relation to anxiety/depression and severity of gastrointestinal (GI) symptoms.

METHODS

Patients with IBS (n = 65) and healthy controls (HCs, n = 37) performed the ten subtests of the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS). Age-normed index scores of five cognitive domains (Immediate memory, Visuospatial function, Language function, Attention, Recall) and a total (Fullscale) score were derived from the performance. Emotional function was assessed using the Hospital Anxiety and Depression Scale (HADS), and the IBS Symptom Scoring System (IBS-SSS) was used to define the severity of GI symptoms.

RESULTS

Patients with IBS reported significantly higher scores than the HC group on symptom measures of anxiety and depression, and significantly lower scores on the Immediate memory, Recall, and Fullscale RBANS indexes. Approximately 30% of the IBS patients obtained index scores at least one standard deviation below the population mean, and more than 50% scored above the screening threshold for an anxiety disorder. The severity of GI symptoms was significantly correlated with the severity level of anxiety symptoms (p=.006), but neither the severity level of emotional nor GI symptoms was significantly correlated with the RBANS index scores in the IBS group.

CONCLUSION

Cognitive and emotional function were more severely affected in patients with IBS than in HCs. The weak correlation between the two functional areas suggests that both should be assessed as part of a clinical examination of patients with IBS.

Variety of Serotonin Levels in Pediatric Gastrointestinal Disorders

(1) Serotonin primarily regulates our emotions. A complex process, which includes dysfunctions in gastrointestinal motility and deregulation of the gene responsible for serotonin reuptake (SERT), is implicated in the pathophysiology of irritable bowel syndrome (IBS). This also encompasses changes in intestinal microbiota, the response to stress, the intricate interplay between the brain and the digestive tract, heightened sensitivity to visceral stimuli, and low-grade inflammation. This paper aims to investigate the effectiveness of probiotic therapy in managing gastrointestinal and neuropsychiatric symptoms related to serotonin levels, with a focus on individuals with serotonin deficiency and those with normal serotonin levels experiencing gastrointestinal disorders. (2) The study involved 135 pediatric patients aged 5-18 years with gastrointestinal disturbances, including constipation, diarrhea, and other symptoms, such as nausea, flatulence, feeling full, or gastrointestinal pain. (3) Serotonin testing was performed, and administering probiotics appeared to be effective in addressing serotonin deficiency and other gastrointestinal disorders. (4) Serotonin's pivotal role in regulating neurotransmitter secretion and its impact on neuropsychiatric health, coupled with gender differences and age-related declines, underscore the complexity of their influence on gastrointestinal and neuropsychiatric conditions.

Inflammatory Bowel Disease and Irritable Bowel Syndrome: What Differences in Mentalization Abilities? A Scoping Review

Mentalization is a psychological process that enables individuals to understand the self and others in terms of intentional mental states. The aim of this scoping review was to provide an overview of the findings on mentalization in patients with inflammatory bowel disease (IBD) and irritable bowel syndrome (IBS). A literature search, in line with the Preferred Reporting Items for Systematic Review and Meta-analysis Protocols extension for Scoping Review guidelines, was conducted in the following bibliographic databases: PubMed, PsycINFO, and Scopus. Databases were queried using the following strings (with Boolean operators): ("mentaliz*" OR "metacogniti*" OR "theory of mind" OR "ToM" OR "reflective function*") AND ("irritable bowel syndrome" OR "IBS" OR "inflammatory bowel disease" OR "IBD"). In line with the eligibility criteria, seven articles were included. Results showed that no significant differences in metacognitive ability were found between patients in the IBD and IBS groups. This review revealed the mentalizing difficulties for patients with IBD and IBS. These results should be interpreted with caution since they are based on a few studies that used different instruments to assess mentalizing processes. Future studies are needed to clarify the role of mentalization in patients with these gastrointestinal conditions.

[Depressive Disorders in Adolescence: Current State of Studies Concerning the Microbiota-Gut-Brain Axis]

Depressive Disorders in Adolescence: Current State of Studies Concerning the Microbiota-Gut-Brain Axis Abstract. Depressive disorders increase during adolescence and often lead to significant impairment in affected individuals - despite treatment. Current research efforts aim to further investigate the pathophysiology of depression, considering the influence of gut microbiota on the gut-brain axis. The present narrative review outlines the current state of studies of the microbiota-gut-brain axis in depressive disorders as well as the direct and indirect interactions in adolescence. Besides providing promising results from animal studies, studies on the microbiota-gut-brain axis in adults suffering from depressive disorders are growing steadily. In depressed adolescents, however, the study situation is still marginal, making a recommendation for the supplementation of probiotics and prebiotics in depressed children and adolescents impossible according to the current state of research. Against the background of a very limited number of studies involving adolescents with depressive disorders, the interactive role of the microbiota-gut-brain axis in adolescent development should receive special attention in future research projects.

Geographic social vulnerability is associated with the alpha diversity of the human microbiome

IMPORTANCE

As a risk factor for conditions related to the microbiome, understanding the role of SVI on microbiome diversity may assist in identifying public health implications for microbiome research. Here we found, using a sub-sample of the Human Microbiome Project phase 1 cohort, that SVI was linked to microbiome diversity across body sites and that SVI may influence race/ethnicity-based differences in diversity. Our findings, build on the current knowledge regarding the role of human geography in microbiome research, suggest that measures of geographic social vulnerability be considered as additional contextual factors when exploring microbiome alpha diversity.

Implication of microbiota gut-brain axis in the manifestation of obsessive-compulsive disorder: Preclinical and clinical evidence

Recent research has highlighted the key role of gut microbiota in the development of psychiatric disorders. The adverse impact of stress, anxiety, and depression has been well documented on the commensal gut microflora. Thus, therapeutic benefits of gut microbiota-based interventions may not be avoided in central nervous system (CNS) disorders. In this review, we outline the current state of knowledge of gut microbiota with respect to obsessive-compulsive disorder (OCD). We discuss how OCD-generated changes corresponding to the key neurotransmitters, hypothalamic-pituitary-adrenal axis, and immunological and inflammatory pathways are connected with the modifications of the microbiota-gut-brain axis. Notably, administration of few probiotics such as Lactobacillus rhamnosus (ATCC 53103), Lactobacillus helveticus R0052, Bifidobacterium longum R0175, Saccharomyces boulardii, and Lactobacillus casei Shirota imparted positive effects in the management of OCD symptoms. Taken together, we suggest that the gut microbiota-directed therapeutics may open new treatment approaches for the management of OCD.

From-Toilet-to-Freezer: A Review on Requirements for an Automatic Protocol to Collect and Store Human Fecal Samples for Research Purposes

The composition, viability and metabolic functionality of intestinal microbiota play an important role in human health and disease. Studies on intestinal microbiota are often based on fecal samples, because these can be sampled in a non-invasive way, although procedures for sampling, processing and storage vary. This review presents factors to consider when developing an automated protocol for sampling, processing and storing fecal samples: donor inclusion criteria, urine-feces separation in smart toilets, homogenization, aliquoting, usage or type of buffer to dissolve and store fecal material, temperature and time for processing and storage and quality control. The lack of standardization and low-throughput of state-of-the-art fecal collection procedures promote a more automated protocol. Based on this review, an automated protocol is proposed. Fecal samples should be collected and immediately processed under anaerobic conditions at either room temperature (RT) for a maximum of 4 h or at 4 °C for no more than 24 h. Upon homogenization, preferably in the absence of added solvent to allow addition of a buffer of choice at a later stage, aliquots obtained should be stored at either -20 °C for up to a few months or -80 °C for a longer period-up to 2 years. Protocols for quality control should characterize microbial composition and viability as well as metabolic functionality.

Irritable bowel syndrome and mental health comorbidity - approach to multidisciplinary management

Irritable bowel syndrome (IBS) affects 5-10% of the global population. Up to one-third of people with IBS also experience anxiety or depression. Gastrointestinal and psychological symptoms both drive health-care use in people with IBS, but psychological comorbidity seems to be more important for long-term quality of life. An integrated care approach that addresses gastrointestinal symptoms with nutrition and brain-gut behaviour therapies is considered the gold standard. However, best practice for the treatment of individuals with IBS who have a comorbid psychological condition is unclear. Given the rising prevalence of mental health disorders, discussion of the challenges of implementing therapy for people with IBS and anxiety and depression is critical. In this Review, we draw upon our expertise in gastroenterology, nutrition science and psychology to highlight common challenges that arise when managing patients with IBS and co-occurring anxiety and depression, and provide recommendations for tailoring clinical assessment and treatment. We provide best practice recommendations, including dietary and behavioural interventions that could be applied by non-specialists and clinicians working outside an integrated care model.

Antibiotic-induced gut dysbiosis and cognitive, emotional, and behavioral changes in rodents: a systematic review and meta-analysis

There are previous epidemiological studies reporting associations between antibiotic use and psychiatric symptoms. Antibiotic-induced gut dysbiosis and alteration of microbiota-gut-brain axis communication has been proposed to play a role in this association. In this systematic review and meta-analysis, we reviewed published articles that have presented results on changes in cognition, emotion, and behavior in rodents (rats and mice) after antibiotic-induced gut dysbiosis. We searched three databases-PubMed, Web of Science, and SCOPUS to identify such articles using dedicated search strings and extracted data from 48 articles. Increase in anxiety and depression-like behavior was reported in 32.7 and 40.7 percent of the study-populations, respectively. Decrease in sociability, social novelty preference, recognition memory and spatial cognition was found in 18.1, 35.3, 26.1, and 62.5 percent of the study-populations, respectively. Only one bacterial taxon (increase in gut Proteobacteria) showed statistically significant association with behavioral changes (increase in anxiety). There were no consistent findings with statistical significance for the potential biomarkers [Brain-derived neurotrophic factor (BDNF) expression in the hippocampus, serum corticosterone and circulating IL-6 and IL-1β levels]. Results of the meta-analysis revealed a significant association between symptoms of negative valence system (including anxiety and depression) and cognitive system (decreased spatial cognition) with antibiotic intake (p < 0.05). However, between-study heterogeneity and publication bias were statistically significant (p < 0.05). Risk of bias was evaluated to be high in the majority of the studies. We identified and discussed several reasons that could contribute to the heterogeneity between the results of the studies examined. The results of the meta-analysis provide promising evidence that there is indeed an association between antibiotic-induced gut dysbiosis and psychopathologies. However, inconsistencies in the implemented methodologies make generalizing these results difficult. Gut microbiota depletion using antibiotics may be a useful strategy to evaluate if and how gut microbes influence cognition, emotion, and behavior, but the heterogeneity in methodologies used precludes any definitive interpretations for a translational impact on clinical practice.

Causal association between psycho-psychological factors, such as stress, anxiety, depression, and irritable bowel syndrome: Mendelian randomization

BACKGROUND

Pathogenesis, diagnosis, and treatment of irritable bowel syndrome (IBS) have been reported to be challenging hotspots in clinical practice. Previous observational studies have found that stress, anxiety, depression, and other mental and psychological diseases are closely associated with IBS. This study aimed to further explore the causal relationships of these associations through Mendelian randomization (MR).

METHODS

The data needed for MR were obtained from publicly published genome-wide association databases. We performed a bidirectional, 2-sample MR analysis using instrumental variables (IV) associated with stress, anxiety, and depression, and other mental and psychological factors as exposures and IBS as the outcome. A reverse MR analysis with IBS as exposure and stress, anxiety, depression, and other mental and psychological factors as the outcomes was also performed. The inverse variance weighting (IVW) method was adopted as the main method of MR, and the causal effect between stress, anxiety, depression, and other mental and psychological factors and IBS was evaluated as the main result of the study. In addition, a series of sensitivity analyses was conducted to comprehensively evaluate the causal relationship between them.

RESULTS

Stress, anxiety, depression, and other mental and psychological factors were the underlying etiologies for IBS (odds ratio [OR] = 1.06, 95% confidence interval [CI]: 1.03-1.08), and they were positively correlated. Univariate analysis further supported the above conclusions (Depression, [OR = 1.31, 95% CI: 1.05-1.63, P = .016], Anxiety, [OR = 1.53, 95% CI: 1.16-2.03, P = .003]). However, in reverse MR analysis, we found that IBS did not affect stress, anxiety, depression, or other mental and psychological factors and that there was no causal relationship between IBS and stress, anxiety, depression, or other mental and psychological factors (P > .05).

CONCLUSION

This study demonstrates that mental and psychological factors are the underlying etiologies for IBS. These findings may provide important information for physicians regarding the clinical treatment of IBS.

Microbial Reprogramming in Obsessive-Compulsive Disorders: A Review of Gut-Brain Communication and Emerging Evidence

Obsessive-compulsive disorder (OCD) is a debilitating mental health disorder characterized by intrusive thoughts (obsessions) and repetitive behaviors (compulsions). Dysbiosis, an imbalance in the gut microbial composition, has been associated with various health conditions, including mental health disorders, autism, and inflammatory diseases. While the exact mechanisms underlying OCD remain unclear, this review presents a growing body of evidence suggesting a potential link between dysbiosis and the multifaceted etiology of OCD, interacting with genetic, neurobiological, immunological, and environmental factors. This review highlights the emerging evidence implicating the gut microbiota in the pathophysiology of OCD and its potential as a target for novel therapeutic approaches. We propose a model that positions dysbiosis as the central unifying element in the neurochemical, immunological, genetic, and environmental factors leading to OCD. The potential and challenges of microbial reprogramming strategies, such as probiotics and fecal transplants in OCD therapeutics, are discussed. This review raises awareness of the importance of adopting a holistic approach that considers the interplay between the gut and the brain to develop interventions that account for the multifaceted nature of OCD and contribute to the advancement of more personalized approaches.

Gegen-Qinlian decoction alleviates anxiety-like behaviors in methamphetamine-withdrawn mice by regulating Akkermansia and metabolism in the colon

BACKGROUND

Anxiety is a prominent withdrawal symptom of methamphetamine (Meth) addiction. Recently, the gut microbiota has been regarded as a promising target for modulating anxiety. Gegen-Qinlian decoction (GQD) is a classical Traditional Chinese Medicine applied in interventions of various gut disorders by balancing the gut microbiome. We aim to investigate whether GQD could alleviate Meth withdrawal anxiety through balancing gut microbiota and gut microenvironment.

METHODS

Meth withdrawal anxiety models were established in mice. GQD were intragastric administrated into Meth-withdrawn mice and controls. Gut permeability and inflammatory status were examined in mice. Germ-free (GF) and antibiotics-treated (Abx) mice were used to evaluate the role of gut bacteria in withdrawal anxiety. Gut microbiota was profiled with 16s rRNA sequencing in feces. Metabolomics in colon tissue and in Akkermansia culture medium were performed.

RESULTS

Meth withdrawal enhanced anxiety-like behaviors in wild-type mice, and altered gut permeability, and inflammatory status, while GQD treatment during the withdrawal period efficiently alleviated anxiety-like behaviors and improved gut microenvironment. Next, we found Germ-free (GF) and antibiotics-treated (Abx) mice did not develop anxiety-like behaviors by Meth withdrawal, indicating the essential role of gut bacteria in Meth withdrawal induced anxiety. Then, it was observed that gut microbiota was greatly affected in Meth-withdrawn mice, especially the reduction in Akkermansia. GQD can rescue the gut microbiota and reverse Akkermansia abundance in Meth-withdrawn mice. Meanwhile, GQD can also restore the Meth-impaired Akkermansia growth in vitro. Further, GQD restored several common metabolite levels both in colon in vivo and in Akkermansia in vitro.

CONCLUSIONS

We revealed a novel effect of GQD on Meth withdrawal anxiety and identified its pharmacological target axis as "Akkermansia-Akkermansia metabolites-gut metabolites-gut microenvironment". Our findings indicated that targeting gut bacteria with TCM, such as GQD, might be a promising therapeutic strategy for addiction and related withdrawal symptoms.

Intermittent Fasting Alleviates Non-Alcoholic Steatohepatitis by Regulating Bile Acid Metabolism and Promoting Fecal Bile Acid Excretion in High-Fat and High-Cholesterol Diet Fed Mice

SCOPE

Intermittent fasting (IF) has a protective role across a wide range of chronic disorders, including obesity, diabetes, and cardiovascular disease, but its protection against non-alcoholic steatohepatitis (NASH) is still lacking. This study seeks to investigate how IF alleviates NASH by regulating gut microbiota and bile acids (BAs) composition.

METHODS AND RESULTS

Male C57BL/6 mice are fed a high-fat and high-cholesterol (HFHC) diet for 16 weeks to establish a NASH model. Mice then continued HFHC feeding and are treated with or without every other day fasting for 10 weeks. Hepatic pathology is assessed using hematoxylin-eosin staining. Gut microbiota of the cecum are profiled using 16S rDNA gene sequencing and the levels of BAs in serum, colon contents, and feces are measured using ultra-performance liquid chromatography-tandem mass spectrometry. Results indicate that IF significantly decreases murine body weight, insulin resistance, hepatic steatosis, ballooning, and lobular inflammation. IF reshapes the gut microbiota, reduces the accumulation of serum BAs, and increases total colonic and fecal BAs. Moreover, IF increases the expression of cholesterol 7α-hydroxylase 1 in liver, but decreases the expressions of both farnesoid-X-receptor and fibroblast growth factor 15 in the ileum.

CONCLUSION

IF alleviates NASH by regulating bile acid metabolism and promoting fecal bile acid excretion.

Fibromyalgia and Irritable Bowel Syndrome Interaction: A Possible Role for Gut Microbiota and Gut-Brain Axis

Fibromyalgia (FM) is a serious chronic pain syndrome, characterised by muscle and joint stiffness, insomnia, fatigue, mood disorders, cognitive dysfunction, anxiety, depression and intestinal irritability. Irritable Bowel Syndrome (IBS) shares many of these symptoms, and FM and IBS frequently co-exist, which suggests a common aetiology for the two diseases. The exact physiopathological mechanisms underlying both FM and IBS onset are unknown. Researchers have investigated many possible causes, including alterations in gut microbiota, which contain billions of microorganisms in the human digestive tract. The gut-brain axis has been proven to be the link between the gut microbiota and the central nervous system, which can then control the gut microbiota composition. In this review, we will discuss the similarities between FM and IBS. Particularly, we will focus our attention on symptomatology overlap between FM and IBS as well as the similarities in microbiota composition between FM and IBS patients. We will also briefly discuss the potential therapeutic approaches based on microbiota manipulations that are successfully used in IBS and could be employed also in FM patients to relieve pain, ameliorate the rehabilitation outcome, psychological distress and intestinal symptoms.

Diet as a modifiable factor in tumorigenesis: Focus on microbiome-derived bile acid metabolites and short-chain fatty acids

Several lines of evidences have implicated the resident microbiome as a key factor in the modulation of host physiology and pathophysiology; including the resistance to cancers. Gut microbiome heavily influences host lipid homeostasis by their modulatory effects on the metabolism of bile acids (BAs). Microbiota-derived BA metabolites such as deoxycholic acid (DCA), lithocholic acid (LCA), and ursodeoxycholic acid (UDCA) are implicated in the pathogeneses of various cancer types. The pathogenic mechanisms are multimodal in nature, with widespread influences on the host immunes system, cell survival and growth signalling and DNA damage. On the other hand, short-chain fatty acids (SCFAs) produced by the resident microbial activity on indigestible dietary fibres as well as during intermittent fasting regimens (such as the Ramazan fasting) elicit upregulation of the beneficial anti-inflammatory and anticancer pathways in the host. The present review first provides a brief overview of the molecular mechanisms of microbiota-derived lipid metabolites in promotion of tumour development. The authors then discuss the potential of diet as a therapeutic route for beneficial alteration of microbiota and the consequent changes in the production of SCFAs, particularly butyrate, in relation to the cancer prevention and treatment.

Fecal microbiota transplantation confirmed that 919 Syrup reduced the ratio of erucamide to 5-AVAB in hippocampus to alleviate postpartum depression by regulating gut microbes

Background

Postpartum depression has a crucial impact on the physical and psychological comfort and the work of postnatal women, the growth and development of infants and mental health in adulthood. Finding a safe and effective anti-postnatal depression drug is currently an important research goal in this field.

Methods

In this study, the forced swimming test (FST) and tail suspension test (TST) were used to evaluated the depressive behaviors of mice, and the changes of metabolites and intestinal microflora in mice with postpartum depression were examined through non-target metabolomics and 16S RNA sequencing respectively.

Results

We found that traditional Chinese medicine compound 919 Syrup could alleviate postpartum depression in mice and inhibit the elevated erucamide level in depressive hippocampus. However, mice treated with antibiotics were not sensitive to the anti-postnatal depression effect of 919 Syrup, and the level of 5-aminovaleric acid betaine (5-AVAB) in their hippocampus was significantly decreased. Transplanting fecal microflora treated with 919 Syrup could effectively improve the depressive behaviors of mice, upregulate the level of gut-derived 5-AVAB in the hippocampus, and downregulate the level of erucamide. Erucamide was significantly negatively correlated with increased Bacteroides in intestine after 919 Syrup treatment or fecal transplantation, and significantly positively correlated with Ruminococcaceae UCG-014 which was increased in feces of mice with postpartum depression. The increase of Bacteroides, Lactobacillus, and Ruminiclostridium in intestine after fecal transplantation had a clearly positive correlation with 5-AVAB.

Conclusion

In brief, 919 Syrup may downregulate the ratio of hippocampal metabolites erucamide to 5-AVAB by regulating intestinal flora to alleviate postpartum depression, laying a scientific foundation for future pathological research and development of therapeutic drugs for postpartum depression.

Effects of a Low-FODMAP Diet on Irritable Bowel Syndrome in Both Children and Adults-A Narrative Review

Irritable bowel syndrome is a typical gastrointestinal disease that causes bloating, flatulence, abdominal pain, diarrhoea, constipation, or alteration of the last two in adults and children. A diet low in fermentable oligosaccharides, disaccharides, monosaccharides, and polyols (FODMAP) is one of the potential treatment strategies to reduce abdominal symptoms and increase the quality of life. The present narrative review aims to present a general overview of current studies that have evaluated the efficacy of a low-FODMAP diet against other diets in gastrointestinal symptoms, nutrient intake in adults and children, and lifestyle quality. The research was performed using seven searchable databases, which included the Cochrane Central Register of Controlled Trials (CENTRAL), Cochrane Database of Systematic Reviews (CDSR), Excerpta Medica Database (EMBASE), Medline, PubMed, Scopus, and Web of Science, up to March 2023. In conclusion, there is significant evidence that the follow-up of a low-FODMAP diet might be a feasible first-line therapeutic strategy to reduce stomach discomfort, pain, bloating, and quality of life for patients with irritable bowel syndrome.

Assessing the relationship between gut microbiota and irritable bowel syndrome: a two-sample Mendelian randomization analysis

BACKGROUND

Growing evidence has suggested that gut microbiota is closely related to the risk of irritable bowel syndrome (IBS), but whether there is a causal effect remains unknown. We adopted a Mendelian randomization (MR) approach to evaluate the potential causal relationships between gut microbiota and the risk of IBS.

METHODS

Genetic instrumental variables for gut microbiota were identified from a genome-wide association study (GWAS) of 18,340 participants. Summary statistics of IBS were drawn from a GWAS including 53,400 cases and 433,201 controls. We used the inverse-variance weighted (IVW) method as the primary analysis. To test the robustness of our results, we further performed the weighted-median method, MR-Egger regression, and MR pleiotropy residual sum and outlier test. Finally, reverse MR analysis was performed to evaluate the possibility of reverse causation.

RESULTS

We identified suggestive associations between three bacterial traits and the risk of IBS (odds ratio (OR): 1.08; 95% confidence interval (CI): 1.02, 1.15; p = 0.011 for phylum Actinobacteria; OR: 0.95; 95% CI: 0.91, 1.00; p = 0.030 for genus Eisenbergiella and OR: 1.10; 95% CI: 1.03, 1.18; p = 0.005 for genus Flavonifractor). The results of sensitivity analyses for these bacterial traits were consistent. We did not find statistically significant associations between IBS and these three bacterial traits in the reverse MR analysis.

CONCLUSIONS

Our systematic analyses provide evidence to support a potential causal relationship between several gut microbiota taxa and the risk of IBS. More studies are required to show how the gut microbiota affects the development of IBS.

Maternal separation leads to dynamic changes of visceral hypersensitivity and fecal metabolomics from childhood to adulthood

We assessed dynamic changes in visceral hypersensitivity and fecal metabolomics through a mouse model of irritable bowel syndrome (IBS) from childhood to adulthood. A mouse model of IBS was constructed with maternal separation (MS) in early life. Male mice aged 25, 40, and 70 days were used. Visceral sensitivity was assessed by recording the reaction between the abdominal withdrawal reflex and colorectal distension. Metabolomics was identified and quantified by liquid chromatography-tandem mass spectrometry. The visceral sensitivity of the MS group was significantly higher than that of the non-separation (NS) group in the three age groups. The top four fecal differential metabolites in the different age groups were lipids, lipid molecules, organic heterocyclic compounds, organic acids and derivatives, and benzenoids. Five identical differential metabolites were detected in the feces and ileal contents of the MS and NS groups at different ages, namely, benzamide, taurine, acetyl-L-carnitine, indole, and ethylbenzene. Taurine and hypotaurine metabolism were the most relevant pathways at P25, whereas histidine metabolism was the most relevant pathway at P40 and P70. Visceral hypersensitivity in the MS group lasted from childhood to adulthood. The different metabolites and metabolic pathways detected in MS groups of different ages provide a theoretical basis for IBS pathogenesis.

Gut Microbiota and Behavioural Issues in Production, Performance, and Companion Animals: A Systematic Review

The literature has identified poor nutrition as the leading factor in the manifestation of many behavioural issues in animals, including aggression, hyperalertness, and stereotypies. Literature focused on all species of interest consistently reported that although there were no significant differences in the richness of specific bacterial taxa in the microbiota of individual subjects with abnormal behaviour (termed alpha diversity), there was variability in species diversity between these subjects compared to controls (termed beta diversity). As seen in humans with mental disorders, animals exhibiting abnormal behaviour often have an enrichment of pro-inflammatory and lactic acid-producing bacteria and a reduction in butyrate-producing bacteria. It is evident from the literature that an association exists between gut microbiota diversity (and by extension, the concurrent production of microbial metabolites) and abnormal behavioural phenotypes across various species, including pigs, dogs, and horses. Similar microbiota population changes are also evident in human mental health patients. However, there are insufficient data to identify this association as a cause or effect. This review provides testable hypotheses for future research to establish causal relationships between gut microbiota and behavioural issues in animals, offering promising potential for the development of novel therapeutic and/or preventative interventions aimed at restoring a healthy gut-brain-immune axis to mitigate behavioural issues and, in turn, improve health, performance, and production in animals.

Probiotics for the treatment of depression and its comorbidities: A systemic review

Depression is one of the most common psychiatric conditions, characterized by significant and persistent depressed mood and diminished interest, and often coexists with various comorbidities. The underlying mechanism of depression remain elusive, evidenced by the lack of an appreciate therapy. Recent abundant clinical trials and animal studies support the new notion that the gut microbiota has emerged as a novel actor in the pathophysiology of depression, which partakes in bidirectional communication between the gut and the brain through the neuroendocrine, nervous, and immune signaling pathways, collectively known as the microbiota-gut-brain (MGB) axis. Alterations in the gut microbiota can trigger the changes in neurotransmitters, neuroinflammation, and behaviors. With the transition of human microbiome research from studying associations to investigating mechanistic causality, the MGB axis has emerged as a novel therapeutic target in depression and its comorbidities. These novel insights have fueled idea that targeting on the gut microbiota may open new windows for efficient treatment of depression and its comorbidities. Probiotics, live beneficial microorganisms, can be used to modulate gut dysbiosis into a new eubiosis and modify the occurrence and development of depression and its comorbidities. In present review, we summarize recent findings regarding the MGB axis in depression and discuss the potential therapeutic effects of probiotics on depression and its comorbidities.

Gut Microbiota in Anxiety and Depression: Unveiling the Relationships and Management Options

The gut microbiota is critical for maintaining human health and the immunological system. Several neuroscientific studies have shown the significance of microbiota in developing brain systems. The gut microbiota and the brain are interconnected in a bidirectional relationship, as research on the microbiome-gut-brain axis shows. Significant evidence links anxiety and depression disorders to the community of microbes that live in the gastrointestinal system. Modified diet, fish and omega-3 fatty acid intake, macro- and micro-nutrient intake, prebiotics, probiotics, synbiotics, postbiotics, fecal microbiota transplantation, and 5-HTP regulation may all be utilized to alter the gut microbiota as a treatment approach. There are few preclinical and clinical research studies on the effectiveness and reliability of various therapeutic approaches for depression and anxiety. This article highlights relevant research on the association of gut microbiota with depression and anxiety and the different therapeutic possibilities of gut microbiota modification.

Characteristics and properties of a polysaccharide isolated from Wolfiporia cocos as potential dietary supplement for IBS

Introduction

As low FODMAP (Fermentable oligosaccharides, disaccharides, monosaccharides and polyols) diet therapy is recommended for most of Irritable Bowel Syndrome (IBS) patients, the consequent insufficient of dietary fibers (DFs) intake exert an adverse impact on intestinal health. It is necessary to find suitable DFs for IBS patients.

Methods

This study extracted a water-insoluble polysaccharide from Wolfiporia cocos (WIP) by alkali-extraction and acid-precipitation method. Its molecular weight was detected by high performance gel permeation chromatography (HPGPC) analysis. The structure of WIP was analyzed by Fourier transform infrared (FT-IR) spectrum, Nuclear Magnetic Resonance (NMR) spectra and X-ray diffraction (XRD). The properties related to stability, digestion, viscosity, osmotic activity, adsorption and fermentation were investigated, aimed to explore the feasibility of WIP as a new DF supplement for patients with IBS. In addition, 16S rRNA sequencing analysis was conducted to explore its effects on IBS-related gut microbiota.

Results and Discussion

The results showed that WIP had a single homogeneous composition and the molecular weight was 8.1 × 103 Da. WIP was indicated as a kind of pyranose form with β anomeric configuration and the main chain of WIP was 1,3-β-glucan with amorphous structure. In addition to good thermal stability, WIP also has low bioavailability and can reach the colon mostly without being digested. Moreover, the low viscosity and osmotic activity, the high water- swelling and water/oil-holding capacity, fructose adsorption capacity and poor fermentation performance of WIP demonstrated that it is suitable for IBS patients. It is worth noting that WIP regulates IBS associated gut microbiota effectively, such as the abundance of Lachnospiraceae and Prevotella. These findings provide a theoretical basis for the development of WIP as a dietary supplement for IBS patients with low FODMAP diet therapy.

GRAPHICAL ABSTRACT

The Role of the Mycobiome in Women’s Health

Although the human bacteriome and virome have gained a great deal of attention over the years, the human mycobiome has been far more neglected despite having significant value and implications in human health. In women, mycobiome profiles in breastmilk, vaginal regions, the gut, skin, and the oral cavity can provide insight into women’s health, diseases, and microbiome dysbiosis. Analyses of mycobiome composition under factors, such as health, age, diet, weight, and drug exposure (including antibiotic therapies), help to elucidate the various roles of women’s mycobiome in homeostasis, microbiome interactions (synergistic and antagonistic), and health. This review summarizes the most recent updates to mycobiome knowledge in these critical areas.

Bladder Pain Sensitivity Is a Potential Risk Factor for Irritable Bowel Syndrome

BACKGROUND

Although dysmenorrhea is a highly prevalent risk factor for irritable bowel syndrome (IBS), the factors underlying this risk are not fully understood. Prior studies support a hypothesis that repeated distressing menstrual pain promotes cross-organ pelvic sensitization with heightened visceral sensitivity.

AIMS

To further explore cross-organ pelvic sensitization we examined the association of dysmenorrhea, provoked bladder pain, and other putative factors with self-reported IBS-domain pain frequency and new onset after 1-year follow up.

METHODS

We measured visceral pain sensitivity with a noninvasive provoked bladder pain test in a cohort of reproductive-aged women, enriched for those reporting moderate-to-severe menstrual pain intensity but without any prior IBS diagnosis (n = 190). We analyzed the relationship between menstrual pain, provoked bladder pain, pain catastrophizing, anxiety, and depression with primary outcomes: (1) frequency of self-reported IBS-domain pain and (2) new onset of IBS-domain pain after 1-year follow up.

RESULTS

All hypothesized factors correlated with the frequency of IBS-domain pain (p's ≤ 0.038). In a cross-sectional model, only menstrual pain (standardized adjusted odds ratio 2.07), provoked bladder pain (1.49), and anxiety (1.90) were independently associated with IBS-domain pain ≥ 2 days/month (C statistic = 0.79). One year later, provoked bladder pain (3.12) was the only significant predictor of new onset IBS-domain pain (C statistic = 0.87).

CONCLUSION

Increased visceral sensitivity among women with dysmenorrhea could lead to IBS. Because provoked bladder pain predicted subsequent IBS, prospective studies should be performed to see if the early treatment of visceral hypersensitivity mitigates IBS.

Gut Bacterial Dysbiosis in Irritable Bowel Syndrome: a Case-Control Study and a Cross-Cohort Analysis Using Publicly Available Data Sets

Research on the gut microbiota in irritable bowel syndrome (IBS) shows discordant results due to inconsistent study designs or small sample sizes. This study aimed to characterize how gut microbiota in IBS patients differs from that in healthy controls by performing a case-control study and cross- and mega-cohort analysis. Multiple publicly shared data sets were examined by using a unified analytical approach. We performed 16S rRNA gene (V3-4) sequencing and taxonomic profiling of the gut bacterial communities. Fecal samples from children with IBS (n = 19) and age-matched healthy controls (n = 24) were used. Next, we analyzed 10 separate data sets using a unified data-processing and analytical approach. In total, 567 IBS patients and 487 healthy controls were examined. In our data sets, no significant differences existed in stool α-diversity between IBS patients and healthy controls. After combining all the data sets using a unified data-processing method, we found significantly lower α-diversity in IBS patients than in healthy controls. In addition, the relative abundance of 21 bacterial species differed between the IBS patients and healthy participants. Although the causal relationship is uncertain, gut bacterial dysbiosis is associated with IBS. Further functional studies are needed to assess whether the change in gut microorganisms contributes to the development of IBS. IMPORTANCE Research on the gut bacteria in irritable bowel syndrome (IBS) shows discordant results due to inconsistent study designs or small sample sizes. To overcome these issues, we analyzed microbiota of 567 IBS patients and 487 healthy people from 10 shared data sets using a unified method. We demonstrated that gut bacteria are less diverse in IBS patients than in healthy people. In addition, the abundance of 21 bacterial species is different between the two groups. Altered bacterial balance, called dysbiosis, has been reported in several disease states. Although the causal relationship is uncertain, gut bacterial dysbiosis also seems to be associated with IBS.

Inflammation, Lifestyle Factors, and the Microbiome-Gut-Brain Axis: Relevance to Depression and Antidepressant Action

Depression is considered a major public health concern, where existing pharmacological treatments are not equally effective across all patients. The pathogenesis of depression involves the interaction of complex biological components, such as the immune system and the microbiota-gut-brain axis. Adjunctive lifestyle-oriented approaches for depression, including physical exercise and special diets are promising therapeutic options when combined with traditional antidepressants. However, the mechanisms of action of these strategies are incompletely understood. Accumulating evidence suggests that physical exercise and specific dietary regimens can modulate both the immune system and gut microbiota composition. Here, we review the current information about the strategies to alleviate depression and their crosstalk with both inflammatory mechanisms and the gut microbiome. We further discuss the role of the microbiota-gut-brain axis as a possible mediator for the adjunctive therapies for depression through inflammatory mechanisms. Finally, we review existing and future adjunctive strategies to manipulate the gut microbiota with potential use for depression, including physical exercise, dietary interventions, prebiotics/probiotics, and fecal microbiota transplantation.

The gut-microbiota-brain axis in a Spanish population in the aftermath of the COVID-19 pandemic: microbiota composition linked to anxiety, trauma, and depression profiles

The prevalence of anxiety and depression soared following the COVID-19 pandemic. To effectively treat these conditions, a comprehensive understanding of all etiological factors is needed. This study investigated fecal microbial features associated with mental health outcomes (symptoms of anxiety, depression, or posttraumatic stress disorder (PTSD)) in a Spanish cohort in the aftermath of the COVID-19 pandemic. Microbial communities from stool samples were profiled in 198 individuals who completed validated, self-report questionnaires. 16S ribosomal RNA gene V3-4 amplicon sequencing was performed. Microbial diversity and community structure were analyzed, together with relative taxonomic abundance. In our cohort of N=198, 17.17% reported depressive symptoms, 37.37% state anxiety symptoms, 40.90% trait anxiety symptoms, and 8.08% PTSD symptoms, with high levels of comorbidity. Individuals with trait anxiety had lower Simpson's diversity. Fusicatenibacter saccharivorans was reduced in individuals with comorbid PTSD + depression + state and trait anxiety symptoms, whilst an expansion of Proteobacteria and depletion of Synergistetes phyla were noted in individuals with depressive symptoms. The relative abundance of Anaerostipes was positively correlated with childhood trauma, and higher levels of Turicibacter sanguinis and lower levels of Lentisphaerae were found in individuals who experienced life-threatening traumas. COVID-19 infection and vaccination influenced the overall microbial composition and were associated with distinct relative taxonomic abundance profiles. These findings will help lay the foundation for future studies to identify microbial role players in symptoms of anxiety, depression, and PTSD and provide future therapeutic targets to improve mental health outcomes.

Significant Differences in Gut Microbiota Between Irritable Bowel Syndrome with Diarrhea and Healthy Controls in Southwest China

BACKGROUND

Irritable bowel syndrome (IBS) is a heterogeneous disease, which is closely related to environmental factors and gut microbiota.

OBJECTIVE

To study gut microbiota in IBS-D of Han nationality in Southwest China and explore its relationship with environmental factors.

METHODS

One hundred and twenty cases of IBS-D and 63 cases of HCs were recruited; baseline data such as age, height, and weight were collected. HAMA, HAMD, IBS-SSS, IBS-QOL, and laboratory tests were performed. Feces were collected for 16S rDNA sequencing. Then, the differences of gut microbiota were analyzed and looked for biomarkers of each. FAPROTAX was used to predict the functional differences of gut microbiota. Spearman analysis was conducted between the phylum level and environmental factor.

RESULTS

There were significant differences in daily life between IBS-D and HCs, especially in the spicy taste. The scores of HAMA and HAMD, urea, and transaminase in IBS-D were significantly higher than those of HCs. The richness of gut microbiota in IBS-D was significantly lower than that of HCs, as well as the beta diversity, but not diversity. The biomarkers of IBS-D were Prevotella, Clostridiales, and Roseburia, and the biomarkers of HCs were Veillonellaceae, Bacteroides coprocola, and Bifidobacteriales. The functions of gut microbiota in IBS-D were significantly different from HCs. Correlation analysis showed that multiple gut microbiota were closely related to HAMA, IBS-SSS, IBS-QOL, inflammatory indexes, and liver enzymes.

CONCLUSION

There are significant differences in richness of gut microbiota, flora structure, and flora function between IBS-D and HCs in Southwest China. These differences may be closely related to environmental factors such as eating habits, living habits, and mental and psychological factors.

CLINICAL TRIAL REGISTRATION

The trial was registered and approved in China Clinical Trial Registry (Registration No. ChiCTR2100045751).

Characteristics of fecal microbiota in different constipation subtypes and association with colon physiology, lifestyle factors, and psychological status

Background

Patients with chronic constipation (CC) show altered gut microbial composition.

Objectives

To compare the fecal microbiota with different constipation subtypes and to identify potential influencing factors.

Design

This is a prospective cohort study.

Methods

The stool samples of 53 individuals with CC and 31 healthy individuals were analyzed using 16S rRNA sequencing. The associations between microbiota composition and colorectal physiology, lifestyle factors, and psychological distress were analyzed.

Results

In all, 31 patients with CC were classified as having slow-transit constipation, and 22 were classified under normal-transit constipation. The relative abundance of Bacteroidaceae was lower, and the relative abundance of Peptostreptococcaceae, Christensenellaceae, and Clostridiaceae was higher in slow-transit than in normal-transit group. In all, 28 and 25 patients with CC had dyssynergic defecation (DD) and non-DD, respectively. The relative abundance of Bacteroidaceae and Ruminococcaceae was higher in DD than in non-DD. Rectal defecation pressure was negatively correlated with the relative abundance of Prevotellaceae and Ruminococcaceae but positively correlated with that of Bifidobacteriaceae in CC patients. Multiple linear regression analysis suggested that depression was a positive predictor of Lachnospiraceae relative abundance, and sleep quality was an independent predictor of decreased relative abundance of Prevotellaceae.

Conclusion

Patients with different CC subtypes showed different characteristics of dysbiosis. Depression and poor sleep were the main factors that affected the intestinal microbiota of patients with CC.

Plain language summary

Characteristics of fecal microbiota in different constipation subtypes and association with colon physiology, lifestyle factors, and psychological status Patients with chronic constipation (CC) show altered gut microbial composition. Previous studies in CC are limited by lacking of subtype stratification, which is reflected in the lack of agreement in findings across the large number of microbiome studies. We analyzed stool microbiome of 53 CC patients and 31 healthy individuals using 16S rRNA sequencing. We found that the relative abundance of Bacteroidaceae was lower, and the relative abundance of Peptostreptococcaceae, Christensenellaceae, and Clostridiaceae was higher in slow-transit than in normal-transit CC patients. The relative abundance of Bacteroidaceae and Ruminococcaceae was higher in dyssynergic defecation (DD) than in non-DD patients with CC. In addition, depression was a positive predictor of Lachnospiraceae relative abundance, and sleep quality was an independent predictor of decreased relative abundance of Prevotellaceae in all CC patients. This study emphasizes patients with different CC subtypes have different characteristics of dysbiosis. Depression and poor sleep may be the main factors that affect the intestinal microbiota of patients with CC.

The effects of chronic unpredicted mild stress on maternal negative emotions and gut microbiota and metabolites in pregnant rats

Background

Chronic long-term stress is associated with a range of disorders, including depression and a variety of other chronic illnesses. It is well known that maternal exposure to psychosocial stress during pregnancy significantly increases the likelihood of adverse pregnancy outcomes. The gut microbiota has been a popular topic, it is a key mediator of the gut-brain axis and plays an important role in human health; changes in the gut microbiota have been related to chronic stress-induced health impairment, however, the relationship between maternal negative emotions and abnormal gut microbiota and its metabolites during maternal exposure to chronic stress during pregnancy remains unclear.

Methods

Pregnant rats were subjected to chronic unpredicted mild stress (CUMS) to establish the rat model of chronic stress during pregnancy. The behavioral changes were recorded using sucrose preference test (SPT) and open-field test (OFT), plasma corticosterone levels were determined by radioimmunoassay, and a comprehensive method combining 16S rRNA gene sequencing and gas chromatography-mass spectrometry (GC-MS) metabolomics was used to study the effects of stress during pregnancy on the function of intestinal microbiota and its metabolites.

Results

Chronic stress during pregnancy not only increased maternal plasma corticosterone (P < 0.05), but also caused maternal depression-like behaviors (P < 0.05). Chronic stress during pregnancy changed the species composition at the family level of maternal gut microbiota, the species abundance of Ruminococcaceae in the stress group (23.45%) was lower than the control group (32.67%) and the species abundance of Prevotellaceae in the stress group (10.45%) was higher than the control group (0.03%) (P < 0.05). Vertical locomotion and 1% sucrose preference percentage in pregnant rats were negatively correlated with Prevotellaceae (r =  - 0.90, P < 0.05). Principal component analysis with partial least squares discriminant analysis showed that the integration points of metabolic components in the stress and control groups were completely separated, indicating that there were significant differences in the metabolic patterns of the two groups, and there were seven endogenous metabolites that differed (P < 0.05).

Conclusions

The negative emotional behaviors that occur in pregnant rats as a result of prenatal chronic stress may be associated with alterations in the gut microbiota and its metabolites. These findings provide a basis for future targeted metabolomics and gut flora studies on the effects of chronic stress during pregnancy on gut flora.

Protective effect of valerian extract capsule (VEC) on ethanol- and indomethacin-induced gastric mucosa injury and ameliorative effect of VEC on gastrointestinal motility disorder

CONTEXT

Valerian extract capsule (VEC) is an effective Chinese patent medicine used for gastrointestinal (GI) diseases.

OBJECTIVE

To investigate the detailed pharmacological activity for VEC clinical effects in GI diseases.

MATERIALS AND METHODS

Sprague-Dawley rats were divided into six groups: control, model, and drug-treated (VEC-L, VEC-M, VEC-H, and teprenone). Rats were orally administered VEC (124, 248, 496 mg/kg) and teprenone (21.43 mg/kg) for 3 consecutive days. After 1 h, the five groups (except the control group) were orally given ethanol (10 mL/kg) for 1 h or indomethacin (80 mg/kg) for 7 h. The spasmolytic activity of VEC (0.01-1 mg/mL) on ACh/BaCl₂-induced New Zealand rabbit smooth muscle contraction was performed. The C57BL/6 mice carbon propelling test evaluated the effects of VEC (248-992 mg/kg) on intestinal motility in normal and neostigmine/adrenaline-induced mice.

RESULTS

Compared with the model group, VEC treatment reduced the gastric lesion index and mucosal damage. Further experiments showed that the pathological ameliorative effect of VEC was accompanied by augmentation of the enzymatic antioxidant system and cytoprotective marker (COX-1, p < 0.01; PGI2 p < 0.05;), along with the alleviation of the levels of MPO (ethanol: 15.56 ± 0.82 vs. 12.15 ± 2.60, p < 0.01; indomethacin: 9.65 ± 3.06 vs. 6.36 ± 2.43, p < 0.05), MDA (ethanol: 1.66 ± 0.44 vs. 0.81 ± 0.58, p < 0.01; indomethacin: 1.71 ± 0.87 vs. 1.09 ± 0.43, p < 0.05), and inflammatory mediators. VEC decreased the high tone induced by ACh/BaCl₂ and promoted intestinal transit in normal and neostigmine/adrenaline-induced mice.

DISCUSSION AND CONCLUSIONS

VEC showed a potential gastroprotective effect, suggesting that VEC is a promising phytomedicine for the treatment of GI diseases.

Updates in interaction of gastroesophageal reflux disease and extragastroesophageal digestive diseases

INTRODUCTION

Gastroesophageal reflux disease (GERD) is one of the common chronic diseases with prevalence increasing in the last decades. Because of its prevalence and chronicity, GERD affects the quality of life and increases health-care costs. Gastroesophageal diseases leading to GERD have been thoroughly studied, while extragastroesophageal digestive diseases (EGEDDs) may coexist with GERD and affect the occurrence and persistence of GERD symptoms and therapeutic effect.

AREAS COVERED

In this review, we aim to summarize the EGEDDs correlated with GERD and explore the potential mechanisms of this interaction.

EXPERT OPINION

Individuals with troublesome GERD symptoms may have some common gastroesophageal etiologies, but EGEDDs may also overlap and impact on the progression of GERD, which are often ignored in clinic. The lesions in the small intestine, colon, and hepatobiliary tract as well as functional bowel disorders had positive or negative associations with GERD through potential mechanisms. These diseases aggravate GERD symptoms, increase the esophageal acid burden, cause esophageal hypersensitivity, and finally affect the response to therapy in GERD patients. Therefore, it is necessary to clear the interaction between GERD and EGEDDs and their mechanisms.

Potential of natural products in the treatment of irritable bowel syndrome

BACKGROUND

Irritable bowel syndrome (IBS) is a kind of functional bowel disease that is characterized by bellyache, abdominal distension, and diarrhea. Although not life-threatening, IBS has a long course and recurrent attacks and seriously affects the life quality of patients. Current drugs for treating IBS possess remarkable limitations, such as limited efficacy and severe adverse reactions. Therefore, developing novel medications to treat IBS is quite essential, and natural products may be a substantial source.

PURPOSE

This is the first systematic review elaborating the recent advancement of natural products as potential drugs for the therapy of IBS.

METHODS

A comprehensive retrieval of studies was carried out in scientific databases including PubMed, Web of Science, Elsevier, and CNKI. By using ("irritable bowel syndrome" OR "IBS") AND ("natural product" OR "natural compound" OR "phytochemical") as keywords, the eligible studies were screened, and the relevant information about therapeutic action and mechanism of natural products treating IBS was extracted.

RESULTS

Natural products against IBS consisted of four categories, namely, terpenoids, flavonoids, alkaloids, and phenols. Furthermore, the underlying mechanisms for natural products treating IBS were tightly associated with increased TJs and mucus protein expression, regulation of the brain-gut axis and gut microbiota structure, and inhibition of inflammatory response and intestinal mucosal damage.

CONCLUSION

Natural products could be extremely prospective candidate drugs used to treat IBS, and further preclinical and clinical researches are needed to guarantee their efficacy and safety.

Estrogen receptor β deficiency impairs gut microbiota: a possible mechanism of IBD-induced anxiety-like behavior

BACKGROUND

Although the lack of estrogen receptor β (ERβ) is a risk factor for the development of inflammatory bowel disease (IBD) and psychiatric disorders, the underlying cellular and molecular mechanisms are not fully understood. Herein, we revealed the role of gut microbiota in the development of IBD and related anxiety-like behavior in ERβ-deficient mice.

RESULTS

In response to dextran sodium sulfate (DSS) insult, the ERβ knockout mice displayed significant shift in α and β diversity in the fecal microbiota composition and demonstrated worsening of colitis and anxiety-like behaviors. In addition, DSS-induced colitis also induced hypothalamic-pituitary-adrenal (HPA) axis hyperactivity in ERβ-deficient mice, which was associated with colitis and anxiety-like behaviors. In addition, RNA sequencing data suggested that ErbB4 might be the target of ERβ that is involved in regulating the HPA axis hyperactivity caused by DSS insult. Gut microbiota remodeling by co-housing showed that both the colitis and anxiety-like behaviors were aggravated in co-housed wild-type mice compared to single-housed wild-type mice. These findings suggest that gut microbiota play a critical role in mediating colitis disease activity and anxiety-like behaviors via aberrant neural processing within the gut-brain axis.

CONCLUSIONS

ERβ has the potential to inhibit colitis development and anxiety-like behaviors via remodeling of the gut microbiota, which suggests that ERβ is a promising therapeutic target for the treatment of IBD and related anxiety-like behaviors. Video Abstract.

Efficacy and safety of fecal microbiota transplant in irritable bowel syndrome: An update based on meta-analysis of randomized control trials

Background and Aims

Fecal microbiota transfer (FMT) is a potential treatment for irritable bowel syndrome (IBS). Several randomized trials have tested FMT effects using different routes of administration, doses, and sample sizes. We aim to assess the overall efficacy of FMT for IBS patients and the safety of the intervention.

Methods

We systematically searched four databases for randomized control trials that studied the efficacy and safety of FMT in IBS patients.

Results

We included 8 randomized trials (472 patients) that compared FMT with placebo in IBS patients. Pooled results showed no statistically significant difference between FMT and control groups in the overall change in IBS symptom severity (IBS-SSS) at 1 month (p = 0.94), 3/4 months (p = 0.82), and at the end of trials (p = 0.67). No significant difference in the total number of respondents between the FMT and control groups (risk ratios = 1.84, [95% confidence interval (CI) = 0.82-2.65], p = 0.19). Although the oral route of administration showed a significant difference in the number of respondents (p = 0.004), there was no statistically significant difference in the IBS-SSS when subgrouping the oral route of administration (mean difference = 47.57, [95% CI = -8.74-103.87], p = 0.10).

Conclusion

FMT is not an effective treatment to relieve all the symptoms of IBS. Even in the groups that showed relatively significant improvement after FMT, the effect was proven to wear off over time and the re-administration carries a low success rate. Future research should consider different bacterial-based interventions such as probiotics or specific antibiotics.