Microbial and metabolomic profiles in correlation with depression and anxiety co-morbidities in diarrhoea-predominant IBS patients

Analysis of gut microbiota and depression and anxiety: Mendelian randomization from three datasets

BACKGROUND

Emerging evidence supports gut microbiota's association with mental distress, particularly depression and anxiety, the microbiota-gut-brain axis was the believed to be the underlying mechanism. This study investigated the causal relationships between specific gut microbiota and depression and anxiety disorders using large-scale genome-wide association study (GWAS) data.

METHODS

A two-sample bidirectional Mendelian randomization (MR) analysis was conducted to explore the causal effects of 211 microbial taxa on depression and anxiety across three large GWAS databases: FinnGen, Pan-UKBB, and PGC. Sensitive analyses were followed to validate the robustness of results. Random-effect meta-analysis was further performed to enhance the statistical power.

RESULTS

The MR analysis revealed that the Bifidobacteriales (IVW: OR 0.90, 95 %CI 0.83 to 0.98) and Bifidobacteriaceae (IVW: OR 0.90, 95 %CI 0.83 to 0.98) had a protective effect against depression. Clostridiales (cML-MA: OR 0.88, 95 %CI 0.81 to 0.95) and Parasutterella (cML-MA: OR 0.75, 95 %CI 0.64 to 0.88) showed negative associations with depression. Increased abundance of Oxalobacteraceae (cML-MA: OR 1.78, 95 %CI 1.24 to 2.56), Deltaproteobacteria (cML-MA: OR 2.17, 95 %CI 1.38 to 3.40), and Desulfovibrionales (cML-MA: OR 2.22, 95 %CI 1.41 to 3.49) was associated with a higher risk of depression. For anxiety, protective effects were found for Actinobacteria (phylum: IVW: OR 0.83, 95 %CI 0.76 to 0.87; class: IVW: OR 0.84, 95 %CI 0.75 to 0.93), Bifidobacteriales (IVW: OR 0.80, 95 %CI 0.75 to 0.85), Bifidobacteriaceae (IVW: OR 0.80, 95 %CI 0.75 to 0.85) and Bifidobacterium [g] (IVW: OR 0.79, 95 %CI 0.74 to 0.84). Lactobacillaceae [f] (cML-MA: OR 1.18, 95 %CI 1.08 to 1.28), Clostridia [c] (cML-MA: OR 1.15, 95 %CI 0.1.06 to 1.26) and Clostridiales [o] (IVW: OR 1.15, 95 %CI 1.05 to 1.27) were associated with increased anxiety risk. Meta-analysis results indicated significant associations, particularly the protective effects of Actinobacteria (OR 0.90, 95 % CI, 0.83 to 0.98) and Clostridiaceae1 (OR 0.91, 95 % CI, 0.83 to 0.99) on depression and several taxa on anxiety. No significant instrumental variables for depression or anxiety on gut microbiota were identified.

CONCLUSIONS

Our findings highlight specific gut microbiota that are associated with depression and anxiety, underscoring the causal relationships between these intestinal microbes and psychiatric disorders. These results suggest potential strategies for mitigating disease symptoms and improving quality of life through microbiome-targeted therapies. Further studies, including randomized controlled trials and investigations into sex-specific effects, are essential to validate and expand upon these findings.

Multifluid Metabolomics Identifies Novel Biomarkers for Irritable Bowel Syndrome

Background/Objectives: Irritable bowel syndrome (IBS) is a complex disorder affecting 10% of the global population, but the underlying mechanisms remain poorly understood. By integrating multifluid metabolomics, we aimed to identify metabolite markers of IBS in a large population-based cohort. Methods: We included individuals from TwinsUK with and without IBS, ascertained using the Rome III criteria, and analysed serum (232 cases, 1707 controls), urine (185 cases, 1341 controls), and stool (186 cases, 1284 controls) metabolites (Metabolon Inc.). Results: After adjusting for covariates, and multiple testing, 44 unique metabolites (25 novel) were associated with IBS, including lipids, amino acids, and xenobiotics. Androsterone sulphate, a sulfated steroid hormone precursor, was associated with lower odds of IBS in both urine (0.69 [95% confidence interval = 0.56-0.85], p = 2.34 × 10-4) and serum (0.75 [0.63-0.90], p = 1.54 × 10-3. Moreover, suberate (C8-DC) was associated with higher odds of IBS in serum (1.36 [1.15-1.61]; p = 1.84 × 10-4) and lower odds of IBS in stool (0.76 [0.63-0.91]; p = 2.30 × 10-3). On the contrary, 32 metabolites appeared to be fluid-specific, including indole, 13-HODE + 9-HODE, pterin, bilirubin (E,Z or Z,Z), and urolithin. The remaining 10 metabolites were associated with IBS in one fluid with suggestive evidence (p < 0.05) in another fluid. Finally, we identified androgenic signalling, dicarboxylates, haemoglobin, and porphyrin metabolism to be significantly over-represented in individuals with IBS compared to controls. Conclusions: Our results highlight the utility of a multi-fluid approach in IBS research, revealing distinct metabolic signatures across biofluids.

Improving Irritable Bowel Syndrome (IBS) Symptoms and Quality of Life with Quebracho and Chestnut Tannin-Based Supplementation: A Single-Centre, Randomised, Double-Blind, Placebo-Controlled Clinical Trial

Background/Objectives: Irritable Bowel Syndrome (IBS) is a disorder of the gut-brain axis for which the gastroenterologist is most often consulted. Gastrointestinal symptoms and decreased quality of life lead to a considerable burden of disease. The exact causes of IBS are not well understood, and no standard therapy has been established. The primary outcome of the study focused on the improvements of the IBS symptoms assessed through the validated questionnaire IBS-Severity Scoring System (IBS-SSS). Similarly, secondary outcomes geared towards the improvement of the quality of life (IBS-Quality of Life (IBS-QoL) and the Gastrointestinal Quality of Life Index (GIQLI)) and specific IBS symptoms (bloating, abdominal distension, feeling of heaviness, abdominal pain, and flatulence), were assessed through self-administered questionnaires. Intestinal habits (consistency and frequency of depositions) through subject stratification into diarrhoea (IBS-D), constipation (IBS-C), mixed type (IBS-M), as well as the treatment tolerability were also evaluated. Methods: A randomised, placebo-controlled, double-blind, clinical trial was conducted on 156 enrolled IBS patients (79 female and 77 male), aged 18-70 years, randomised (1:1 allocation ratio) to receive either two capsules per day of the food supplement (containing 480 mg of a complex of tannin extracts) or a placebo for 56 days. Linear random intercept mixed models (LMM) were used to analyse all experimental variables Results: Supplementation resulted in a significant improvement (p < 0.05) in the primary outcome IBSS score, with respect to the placebo group, changing the IBS condition going from mild (242.3 ± 89.8) to moderate (148.1 ± 60.6). Similarly, all indicators concerning quality of life, and specific intestinal symptoms resulted in a significant improvement (p < 0.05). Furthermore, the tannin-based treatment showed the ability to modulate the response to different symptomatology such as diarrhoea and constipation, without side effects being reported. Conclusions: The use of a supplement based on chestnut and quebracho tannins presents great application potential in the management of IBS-related disorders, with the peculiarity of resolving opposite symptoms, such as diarrhoea and constipation, indiscriminately.

Meta-analysis of gut microbiota alterations in patients with irritable bowel syndrome

Introduction

Irritable bowel syndrome (IBS) is a common chronic disorder of gastrointestinal function with a high prevalence worldwide. Due to its complex pathogenesis and heterogeneity, there is urrently no consensus in IBS research.

Methods

We collected and uniformly reanalyzed 1167 fecal 16S rRNA gene sequencing samples (623 from IBS patients and 544 from healthy subjects) from 9 studies. Using both a random effects (RE) model and a fixed effects (FE) model, we calculated the odds ratios for metrics including bacterial alpha diversity, beta diversity, common genera and pathways between the IBS and control groups.

Results

Significantly lower alpha-diversity indexes were observed in IBS patients by random effects model. Twenty-six bacterial genera and twelve predicted pathways were identified with significant odds ratios and classification potentials for IBS patients. Based on these feature, we used transfer learning to enhance the predictive capabilities of our model, which improved model performance by approximately 10%. Moreover, through correlation network analysis, we found that Ruminococcaceae and Christensenellaceae were negatively correlated with vitamin B6 metabolism, which was decreased in the patients with IBS. Ruminococcaceae was also negatively correlated with tyrosine metabolism, which was decreased in the patients with IBS.

Discussion

This study revealed the dysbiosis of fecal bacterial diversity, composition, and predicted pathways of patients with IBS by meta-analysis and identified universal biomarkers for IBS prediction and therapeutic targets.

The Value of PHQ-9 and GAD-7 for Screening Emotional Disorders in IBS-D and the Specificity of the Gut Flora Associated with Emotional Comorbidity: Preliminary Findings

Background

To identify irritable bowel syndrome with diarrhea (IBS-D) combined with anxiety and/or depression through a psychological screening tool and to further explore the relationships between patients with comorbidities and gut microbiota.

Methods

The GAD-7, SAS, PHQ-9 and SDS were administered to evaluate anxiety and depression. Faeces were subsequently collected from 44 patients with emotional disorders (IBS-EDs), 22 patients without emotional disorders (IBS-nEDs) and 18 healthy controls (HCs) via 16S rRNA sequencing, depending on the participants' wishes. The differences in gut microbiota among different groups were analysed. Spearman analysis was conducted at the genus level and was based on psychological assessment scores. Patients with IBS-D were recruited from December 2020 to November 2022.

Results

This study included 124 outpatients with IBS-D. According to the GAD-7 and SAS scores, 40.3% and 19.3% of the participants, respectively, had anxiety (P < 0.05). Similarly, a significantly greater percentage of participants had depression according to the PHQ-9 than according to the SDS (61.3% vs 33.1%) (P < 0.05). Overall, approximately 66.1% of the participants had emotional disorders (anxiety and/or depression) according to the GAD-7 and PHQ-9. Correlation analysis revealed that the abundances of Eubacterium_hallii_group, Monoglobus and Lachnoclostridium were closely related to the PHQ-9 scores and that the abundances of Subdoligranulum and Holdemanella were closely related to the GAD-7 scores.

Conclusion

In comparison to the SAS and SDS, both the GAD-7 and PHQ-9 identified a greater number of individuals with emotional disorders within the IBS-D population. Furthermore, our findings demonstrated that Lachnoclostridium is not only a biomarker for IBS-ED patients but also that its abundance changes are related to PHQ-9 scores, which may provide insights for further brain gut investigations.

Cross-Cohort Gut Microbiome Signatures of Irritable Bowel Syndrome Presentation and Treatment

Irritable bowel syndrome (IBS) is a prevalent disorder of gut-brain interaction without a reliable cure. Evidence suggests that an alteration of the gut microbiome may contribute to IBS pathogenesis, motivating the development of microbiome-targeted therapies to alleviate IBS symptoms. However, IBS-specific microbiome signatures are variable across cohorts. A total of 9204 datasets were meta-analyzed, derived from fourteen IBS microbiome discovery cohorts, three validation cohorts for diet-microbiome interactions, and five rifaximin therapy cohorts. The consistent bacterial species and functional signatures associated with IBS were identified. Network analysis revealed two distinct IBS-enriched microbiota clusters; obligate anaerobes that are found commonly in the gut, and facultative anaerobes typically present in the mouth, implying a possible association between oral bacterial translocation to gut and IBS pathogenesis. By analyzing diet-microbiome interactions, microbiota-targeted diets that can potentially modulate the altered gut microbiota of IBS subjects toward a healthy status were identified. Furthermore, rifaximin treatment of IBS subjects was linked with a reduction in the abundance of facultatively anaerobic pathobionts. Gut microbiome signatures were identified across IBS cohorts that may inform the development of therapies for microbiome modulation in IBS. The microbiota-targeted diet patterns described may enable nutritional intervention trials in IBS and for assisting dietary management.

Possible roles of neuropeptide/transmitter and autoantibody modulation in emotional problems and aggression

The theoretical foundations of understanding psychiatric disorders are undergoing changes. Explaining behaviour and neuroendocrine cell communication leaning towards immunology represents a different approach compared to previous models for understanding complex central nervous system processes. One such approach is the study of immunoglobulins or autoantibodies, and their effect on peptide hormones in the neuro-endocrine system. In the present review, we provide an overview of the literature on neuropeptide/transmitter and autoantibody modulation in psychiatric disorders featuring emotional problems and aggression, including associated illness behaviour. Finally, we discuss the role of psycho-immunology as a growing field in the understanding of psychiatric disorders, and that modulation and regulation by IgG autoAbs represent a relatively new subcategory in psycho-immunology, where studies are currently being conducted.

Effect of Tryptophan Restriction in the Therapy of Irritable Bowel Syndrome: a Systematic Review

Background & Aims

The metabolic pathways of tryptophan (TRP) have been implicated in the pathophysiology of irritable bowel syndrome (IBS), positing that the strategic modulation of TRP consumption may exert regulatory effects on serotonin levels, consequently altering the clinical manifestation of IBS. This systematic review was meticulously orchestrated to evaluate the effect of TRP restriction on IBS.

Methods

A comprehensive search of the MEDLINE/PubMed, Cochrane Library, and Embase databases was conducted. Controlled trials that compared the efficacy of TRP restriction in IBS patients were scrutinized. The primary outcomes were gastrointestinal symptoms, quality of life, and pain, whereas the secondary outcomes included anxiety, mood, and safety. The risk of bias was meticulously assessed according to the guidelines recommended by the Cochrane Collaboration.

Results

A total of five trials, enrolling 135 participants, were incorporated into the qualitative synthesis. Low-TRP intake attenuated gastrointestinal discomfort and enhanced psychological well-being in IBS patients, while the effects of acute TRP depletion were controversial. Safety data from one randomized controlled trial reported no occurrence of adverse events.

Conclusion

This systematic review suggests that moderating, rather than depleting, TRP intake may potentially be a feasible and safe adjunctive treatment for patients with IBS. Future research incorporating a high-quality study design and consensus on clinical outcome measurements for IBS is warranted.

Impacts of microbiota and its metabolites through gut-brain axis on pathophysiology of major depressive disorder

Major depressive disorder (MDD) is characterized by a high rate of recurrence and disability, which seriously affects the quality of life of patients. That's why a deeper understanding of the mechanisms of MDD pathology is an urgent task, and some studies have found that intestinal symptoms accompany people with MDD. The microbiota-gut-brain axis is the bidirectional communication between the gut microbiota and the central nervous system, which was found to have a strong association with the pathogenesis of MDD. Previous studies have focused more on the communication between the gut and the brain through neuroendocrine, neuroimmune and autonomic pathways, and the role of gut microbes and their metabolites in depression is unclear. Metabolites of intestinal microorganisms (e.g., tryptophan, kynurenic acid, indole, and lipopolysaccharide) can participate in the pathogenesis of MDD through immune and inflammatory pathways or by altering the permeability of the gut and blood-brain barrier. In addition, intestinal microbes can communicate with intestinal neurons and glial cells to affect the integrity and function of intestinal nerves. However, the specific role of gut microbes and their metabolites in the pathogenesis of MDD is not well understood. Hence, the present review summarizes how gut microbes and their metabolites are directly or indirectly involved in the pathogenesis of MDD.

Oral administration of Robinia pseudoacacia L. flower exosome-like nanoparticles attenuates gastric and small intestinal mucosal ferroptosis caused by hypoxia through inhibiting HIF-1α- and HIF-2α-mediated lipid peroxidation

The prevention and treatment of gastrointestinal mucosal injury caused by a plateau hypoxic environment is a clinical conundrum due to the unclear mechanism of this syndrome; however, oxidative stress and microbiota dysbiosis may be involved. The Robinia pseudoacacia L. flower, homologous to a functional food, exhibits various pharmacological effects, such as antioxidant, antibacterial, and hemostatic activities. An increasing number of studies have revealed that plant exosome-like nanoparticles (PELNs) can improve the intestinal microbiota and exert antioxidant effects. In this study, the oral administration of Robinia pseudoacacia L. flower exosome-like nanoparticles (RFELNs) significantly ameliorated hypoxia-induced gastric and small intestinal mucosal injury in mice by downregulating hypoxia-inducible factor-1α (HIF-1α) and HIF-2α expression and inhibiting hypoxia-mediated ferroptosis. In addition, oral RFELNs partially improved hypoxia-induced microbial and metabolic disorders of the stomach and small intestine. Notably, RFELNs displayed specific targeting to the gastrointestinal tract. In vitro experiments using gastric and small intestinal epithelial cell lines showed that cell death caused by elevated HIF-1α and HIF-2α under 1% O2 mainly occurred via ferroptosis. RFELNs obviously inhibited HIF-1α and HIF-2α expression and downregulated the expression of NOX4 and ALOX5, which drive reactive oxygen species production and lipid peroxidation, respectively, suppressing ferroptosis under hypoxia. In conclusion, our findings underscore the potential of oral RFELNs as novel, naturally derived agents targeting the gastrointestinal tract, providing a promising therapeutic approach for hypoxia-induced gastric and small intestinal mucosal ferroptosis.

The Combined Use of Cinnamaldehyde and Vitamin C Is Beneficial for Better Carcass Character and Intestinal Health of Broilers

The use of cinnamaldehyde and Vitamin C can improve immunity and intestinal health. A two-way factorial design was employed to investigate the main and interactive effects of cinnamaldehyde and vitamin C on the growth, carcass, and intestinal health of broiler chickens. A total of 288 one-day-old female Arbor Acres broiler chicks were randomly distributed among four treatment groups, consisting of six replicate cages with 12 birds each. Four treatments were basal diet or control (CON), supplemental cinnamaldehyde (CA) 300 g/ton (g/t), vitamin C (VC) 300 g/t, and cinnamaldehyde 300 g/t, and vitamin C 300 g/t (CA + VC), respectively. The results showed that supplemental CA did not affect the growth performance or slaughter performance of broilers at 21 days (d), 42 days (d), and 1-42 days (d); however, it could improve intestinal barrier function at 42 d of age and reduce the mRNA expression of inflammatory factors in the intestine at 21 d and 42 d of age. Supplemental VC showed a trend towards increasing body weight gain (BWG) at 21 d (p = 0.094), increased breast muscle rate (at 21-d 5.33%, p < 0.05 and at 42-d 7.09%, p = 0.097), and decreased the abdominal fat (23.43%, p < 0.05) and drip loss (20.68%, p < 0.05) at 42-d. Moreover, VC improves intestinal morphology and intestinal barrier function and maintains a balanced immune response. The blend of CA and VC significantly upregulated the mRNA expression of myeloid differentiation factor 88 (MyD-88) in the intestine at 21 d of age, the mRNA expression of catalase (CAT), Occludin, Claudin-1, Mucin-2, nuclear factor-kappa B (NF-κB) and toll-like receptor 4 (TLR-4) in the intestine at 42 d of age (p < 0.01), and downregulated the mRNA expression of interleukin 10 (IL-10), interleukin 6 (IL-6), tumor necrosis factor-alpha (TNF-α) in the intestine at 21-d and 42-d of age, and interleukin-1 beta (IL-1β) mRNA in intestine at 42 d of age (p < 0.01). This study suggested that the combination of CA and VC had the potential to regulate intestinal health and result in better carcass character of broilers.

The Effects of Fermented Rice Drink With Lactiplantibacillus plantarum JSA22 in Overweight Irritable Bowel Syndrome Patients: A Randomized, Double-blind, Placebo-controlled Study

Background/Aims

This study aims to investigate the effect of a fermented rice drink with Lactiplantibacillus plantarum JSA22 on symptoms, blood tests, microbiomes, and fecal metabolites in patients with irritable bowel syndrome (IBS) who were overweight.

Methods

Sixty overweight (body mass index ≥ 23 kg/m2) patients aged between 20 and 65 with IBS were enrolled. Patients were divided into 2 groups and administered either a fermented rice drink or an nonfermented rice drink for a month. The symptom questionnaire, blood samples, and stool samples for microbiome and metabolite were collected before and after the month of rice drink administration. The primary efficacy variable was the subject's global assessment of IBS symptoms.

Results

In both groups, global IBS symptoms, including abdominal pain, bowel habit, urgency, and abdominal distension, improved significantly (P < 0.01). The abdominal bloating was more significantly improved in the fermented rice drink group than in the nonfermented rice drink group (P < 0.05). Significant changes were not observed in metabolic syndrome-related blood tests or fecal metabolites in either group. However, microbiome analysis showed significant differences in genus levels before and after consuming fermented rice drink, such as in Blautia in stool (P = 0.020) and Prevotella (P = 0.017) and Oribacterium (P = 0.018) in saliva.

Conclusions

The fermented rice drink with L. plantarum JSA22 showed a beneficial effect in reducing abdominal distension in IBS patients. Bacteria that reduce visceral fat accumulation increased in the stool and saliva of patients who consumed fermented rice drinks.

Gut Microbiome and Lipidome Signatures in Irritable Bowel Syndrome Patients from a Low-Income, Food-Desert Area: A Pilot Study

Irritable bowel syndrome (IBS) is a common gastroenterological disorder with triggers such as fructose. We showed that our IBS patients suffering from socioeconomic challenges have a significantly high consumption of high-fructose corn syrup (HFCS). Here, we characterize gut microbial dysbiosis and fatty acid changes, with respect to IBS, HFCS consumption, and socioeconomic factors. Fecal samples from IBS patients and healthy controls were subjected to microbiome and lipidome analyses. We assessed phylogenetic diversity and community composition of the microbiomes, and used linear discriminant analysis effect size (LEfSe), analysis of compositions of microbiomes (ANCOM) on highly co-occurring subcommunities (modules), least absolute shrinkage and selection operator (LASSO) on phylogenetic isometric log-ratio transformed (PhILR) taxon abundances to identify differentially abundant taxa. Based on a Procrustes randomization test, the microbiome and lipidome datasets correlated significantly (p = 0.002). Alpha diversity correlated with economic factors (p < 0.001). Multiple subsets of the phylogenetic tree were associated with HFCS consumption (p < 0.001). In IBS patients, relative abundances of potentially beneficial bacteria such as Monoglobaceae, Lachnospiraceae, and Ruminococcaceae were lower (p = 0.007), and Eisenbergiella, associated with inflammatory disorders, was higher. In IBS patients, certain saturated fatty acids were higher and unsaturated fatty acids were lower (p < 0.05). Our study aims first to underscore the influence of HFCS consumption and socioeconomic factors on IBS pathophysiology, and provides new insights that inform patient care.

Role of in vitamin D in irritable bowel syndrome

Irritable bowel syndrome (IBS) is a common chronic functional gastrointestinal disorder affecting 10%-22% of adults. Its development is closely related to the gut microbiota, and the inflammatory and immune responses triggered by the gut microbiota can lead to IBS. Vitamin D (VD) effectively treats IBS with fewer side effects by improving gut microbiota, immune regulation, and anti-inflammatory effects. In the future, it is necessary to carry out epidemiological studies on the relationship between VD and IBS, clinical studies on the efficacy of supplementing VD to improve IBS, and animal studies on the mechanism of VD improving IBS. Therefore, this paper discussed the relationship between VD and IBS.

Seasonal differences in intestinal flora are related to rats' intestinal water metabolism

Many studies have reported obvious seasonal differences in the intestinal flora of rats, and this stable distribution of the seasonal flora helps in maintaining the normal physiological function of the host. However, the mechanism underlying these seasonal differences in intestinal flora remains unclear. To explore the correlation among seasonal factors and intestinal water metabolism and intestinal flora, 20 Sprague Dawley (SD) rats were divided into spring, summer, autumn, and winter groups. The environment for the four seasons was simulated using the Balanced Temperature and Humidity Control system. The intestinal water metabolism was evaluated by determining the intestinal transmission function, fecal water content, water content of colonic tissue, and the colonic expression levels of AQP3, AQP4, and AQP8. The composition and relative abundance of intestinal microflora in rats in each season were assessed through 16S rDNA amplifier sequencing, and the relationship between the dominant flora and intestinal water metabolism in each season was analyzed using Spearman correlation analysis. The high temperature and humidity season could lead to an increase in intestinal water metabolism and intestinal water content in rats, whereas the low temperature and humidity season could lead to a decrease, which was closely related to the change in microflora. To explore the molecular mechanism of seasonal changes in intestinal water metabolism, the concentration of colonic 5-HT, VIP, cAMP, and PKA associated with intestinal water metabolism in rats were also examined. Seasonal changes could affect the concentration of colonic 5-HT and VIP in rats, and then regulate AQPs through cAMP/PKA pathway to affect the intestinal water metabolism. These results suggest that seasonal factors affect the level of intestinal water metabolism in rats and result in seasonal differences in intestinal flora.

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).

Gut microbiome and fecal metabolic alteration in systemic lupus erythematosus patients with depression

Background

Mental health disorders in systemic lupus erythematosus (SLE) are gradually getting recognized; however, less is known regarding the actual structure and compositional alterations in gut microbiome and metabolism and the mechanisms of how they affect depression development in SLE patients.

Methods

Twenty-one SLE patients with depression (SLE-d), 17 SLE patients without depression (SLE-nd), and 32 healthy controls (HC) were included in this study. Fecal samples were collected for 16S rRNA gene sequencing and ultra-high-performance liquid chromatography-quadrupole time-of-flight mass spectrometry (UHPLC-QTOF-MS) based metabolomics.

Results

The structure of gut microbiome in the SLE-d group changed compared with that in the other two groups. The microbiome composition of SLE-d group showed decreased species richness indices, characterized by low ACE and Chao1 indices, a decrease in the ratio of phylum Firmicutes to Bacteroidetes, genus Faecalibacterium and Roseburia. A downregulation of the metabolite fexofenadine involved in bile secretion was positively correlated with the genus Faecalibacterium, Subdoligranulum and Agathobacter. Compared with the SLE-nd group, the SLE-d group had elevated serum levels of IL-2 and IL-6 and decreased BDNF. Interestingly, abundance of the genus Faecalibacterium and Roseburia was negatively correlated with IL-6, abundance of the genus Roseburia was negatively correlated with IL-2, and abundance of the genus Bacteroides was positively correlated with IL-2.

Conclusion

This study identified specific fecal microbes and their metabolites that may participate in the development of SLE-d. Our findings provide a new perspective for improving depression in SLE patients by regulating the gut-brain axis.

Gut microbiome alterations in ICU patients with enteral nutrition-related diarrhea

Enteral Nutrition-related Diarrhea (END) is an extremely common complication in Intensive Care Unit (ICU) patients. However, it is currently unclear whether the patient’s gut microbiota is disturbed. Our study aimed to explore the characteristics of gut microbiota changes in END patients. We divided ICU patients into no-END group (n = 7) and END group (n = 7) according to whether they had END, then stool samples were collected separately. The V3-V4 region of stool bacterial 16S rRNA gene was amplified by PCR and sequenced on an Illumina MiSeq PE300 platform. Microbiome data obtained by quality control were analyzed, including microbial community composition, diversity and gene function prediction.The results showed that the dominant gut microbiota in ICU patients who were given total enteral nutrition were Firmicutes, Proteobacteria, Bacteroidetes, Actinobacteria, and Verrucomicrobia. Bacterial richness and diversity in END patients were all significantly lower than those in no-END patients. In addition, END caused significant changes in bacterial composition. LEfSe found 34 biomarkers represented by Bacteroidetes and Subdoligranulum in the no-END group as well as 11 biomarkers represented by Enterococcus and Klebsiella in the END group. Finally, through PICRUST function prediction, we found that diarrhea led to abnormal changes in numerous KEGG pathways mainly related to immunity and metabolism. In short, ICU patients with END have severe gut dysbiosis, and our study provides a reliable experimental basis for the patient’s microbiota therapy.

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.

Microbiota profile of new-onset celiac disease in children in Saudi Arabia

Background

Intestinal dysbiosis has been reported to be associated with celiac disease (CeD) in Western populations but little is known in other populations who have different dietary lifestyle and genetic background. The purpose of this study was to determine whether a different microbiota profile is associated with CeD in children in Saudi Arabia.

Results

Forty children with CeD, 20 healthy controls, and 19 non-CeD controls were enrolled. The median age at diagnosis was 10.3, 11.3 and 10.6 years in children with CeD, fecal, and mucosal control groups, respectively. Significant differences in microbial composition between children with CeD and controls both at fecal and mucosal level were identified. Fecal samples were more diverse and richer in bacteria as compared with mucosal samples. Proteobacteria were more abundant in duodenal mucosal samples and Firmicutes and Bacteroides were more abundant in stools. The abundance of many taxa was significantly different between children with CeD and non-CeD controls. In mucosal samples, Bifidobacterium angulatum (unadjusted p = 0.006) and Roseburia intestinalis (unadjusted p = 0.031) were examples of most significantly increased species in children with CeD and non-CeD controls, respectively. In fecal samples, there were 169 bacterial species with significantly different abundance between children with CeD and non- CeD controls.

Conclusions

To our knowledge, this is the first report on the microbial profile in a non-Western population of children with new onset CeD. The fact that mucosal and fecal samples were collected from newly diagnosed children with CeD on normal gluten-containing diet suggests strong association between the identified bacteria and CeD. The identification of many unreported bacterial species significantly associated with CeD, indicates the need for further studies from different populations to expand our understanding of the role of bacteria in the pathogenesis of CeD, hopefully leading to the discovery of new adjuvant treatment options.

Modulating the gut microenvironment as a treatment strategy for irritable bowel syndrome: a narrative review

Irritable bowel syndrome (IBS) is a disorder of gut-brain interaction with a complex pathophysiology. Growing evidence suggests that alterations of the gut microenvironment, including microbiota composition and function, may be involved in symptom generation. Therefore, attempts to modulate the gut microenvironment have provided promising results as an indirect approach for IBS management. Antibiotics, probiotics, prebiotics, food and faecal microbiota transplantation are the main strategies for alleviating IBS symptom severity by modulating gut microbiota composition and function (eg. metabolism), gut barrier integrity and immune activity, although with varying efficacy. In this narrative review, we aim to provide an overview of the current approaches targeting the gut microenvironment in order to indirectly manage IBS symptoms.

NMR Metabolomics Reveal Urine Markers of Microbiome Diversity and Identify Benzoate Metabolism as a Mediator between High Microbial Alpha Diversity and Metabolic Health

Microbial metabolites measured using NMR may serve as markers for physiological or pathological host–microbe interactions and possibly mediate the beneficial effects of microbiome diversity. Yet, comprehensive analyses of gut microbiome data and the urine NMR metabolome from large general population cohorts are missing. Here, we report the associations between gut microbiota abundances or metrics of alpha diversity, quantified from stool samples using 16S rRNA gene sequencing, with targeted urine NMR metabolites measures from 951 participants of the Study of Health in Pomerania (SHIP). We detected significant genus–metabolite associations for hippurate, succinate, indoxyl sulfate, and formate. Moreover, while replicating the previously reported association between hippurate and measures of alpha diversity, we identified formate and 4-hydroxyphenylacetate as novel markers of gut microbiome alpha diversity. Next, we predicted the urinary concentrations of each metabolite using genus abundances via an elastic net regression methodology. We found profound associations of the microbiome-based hippurate prediction score with markers of liver injury, inflammation, and metabolic health. Moreover, the microbiome-based prediction score for hippurate completely mediated the clinical association pattern of microbial diversity, hinting at a role of benzoate metabolism underlying the positive associations between high alpha diversity and healthy states. In conclusion, large-scale NMR urine metabolomics delivered novel insights into metabolic host–microbiome interactions, identifying pathways of benzoate metabolism as relevant candidates mediating the beneficial health effects of high microbial alpha diversity.

Disordered Gut Microbiota Correlates With Altered Fecal Bile Acid Metabolism and Post-cholecystectomy Diarrhea

Post-cholecystectomy diarrhea (PCD) is a common complication of gallbladder removal, and gut microbiota changes have been determined in PCD patients. Bile acid diarrhea (BAD) is supposed to be the main pathogenic factor for PCD due to the disrupted fecal bile acid metabolism in diarrheal patients. However, the profiling of bile acid metabolite alteration in PCD is unclear and whether changed gut microbiota and fecal bile acid metabolism are correlated is also underdetermined. The fecal bile acid metabolites from fecal samples were profiled by targeted UPLC/MS (ultra-high-performance liquid chromatography coupled with a triple-quadrupole mass spectrometer) and the composition of fecal bile acid metabolites in PCD patients was demonstrated to be distinct from those in Non-PCD and HC groups. In addition, the quantification of bile acid excretion in feces of diarrheal patients was significantly elevated. Furthermore, 16S rRNA sequencing results revealed that PCD patients had the lowest operational taxonomic units (OTU) and significant reduction in microbial richness and evenness. Bacterial composition was remarkably shifted in PCD patients, which mainly lay in dominated phyla Firmicutes and Bacteroidota. Besides, the co-abundance network among genus bacteria declined in PCD. Among the genera, Prevotella, Enterococcus, and Erysipelotrichaceae_UCG-003 were enriched, but Alistipes, Bacteroides, Ruminococcus, and Phascolarctobacterium were reduced. Moreover, these disease-linked genera were closely associated with several diarrheal phenotypes. Notably, changed bile acid metabolites exhibited strong correlations with gut microbiota as well. Conclusively, this study reveals associations between PCD-linked microbes and bile acid metabolites, which may synergistically correlate to postoperative diarrhea.

Understanding of the Site-Specific Microbial Patterns towards Accurate Identification for Patients with Diarrhea-Predominant Irritable Bowel Syndrome

Fecal microbial community could not fully represent the intestinal microbial community. However, most studies analyzing diarrhea-dominant irritable bowel syndrome (IBS-D) were mainly based on fecal samples. We aimed to characterize the IBS-D microbial community patterns using samples at multiple intestinal sites. This study recruited 74 IBS-D patients and 20 healthy controls (HC). 22.34%, 8.51%, 14.89%, and 54.26% of them contributed to one, two, three, and four sites: duodenal mucosa (DM), duodenal lumen (DL), rectal mucosa (RM), and rectal lumen (RL) of intestinal samples, respectively. Then 16S rRNA gene analysis was performed on these 283 samples. The result showed that IBS-D microbial communities have specific patterns at each intestinal site differing from that of HC. Across hosts and sites, Bacillus, Burkholderia, and Faecalibacterium were the representative genera in duodenum of IBS-D, duodenum of HC, and rectum of HC, respectively. Samples from mucosa and lumen in rectum were highly distinguishable, regardless of IBS-D and HC. Additionally, IBS-D patients have lower microbial co-abundance network connectivity. Moreover, RM site-specific biomarker: Bacteroides used alone or together with Prevotella and Oscillospira in RM showed outstanding performance in IBS-D diagnosis. Furthermore, Bacteroides and Prevotella in RM were strongly related to the severity of abdominal pain, abdominal discomfort, and bloating in IBS-D patients. In summary, this study also confirmed fecal microbial community could not fully characterize intestinal microbial communities. Among these site-specific microbial communities, RM microbial community would be more applicable in the diagnosis of IBS-D. IMPORTANCE Microbial community varied from one site to another along the gastrointestinal tract, but current studies about intestinal microbial community in IBS-D were mainly based on fecal samples. Based on 283 intestinal samples collected from DM, DL, RM, and RL of HC and IBS-D, we found different intestinal sites had their site-specific microbial patterns in IBS-D. Notably, RM site-specific microbes Bacteroides, Prevotella, and Oscillospira could be used to discriminate IBS-D from HC accurately. Our findings could help clinicians realize the great potential of the intestinal microbial community in RM for better diagnosis of IBS-D patients.

The Effects of Human Milk Oligosaccharides on Gut Microbiota, Metabolite Profiles and Host Mucosal Response in Patients with Irritable Bowel Syndrome

Background: Human milk oligosaccharide supplementation safely modulates fecal bifidobacteria abundance and holds the potential to manage symptoms in irritable bowel syndrome (IBS). Here, we aimed to determine the role of a 4:1 mix of 2′-O-fucosyllactose and lacto-N-neotetraose (2′FL/LNnT) on the modulation of the gut microbiota composition and host mucosal response, as well as the link between the bifidobacteria abundance and metabolite modulation, in IBS patients. Methods: Biological samples were collected from IBS patients (n = 58) at baseline and week 4 post-supplementation with placebo, 5 g or 10 g doses of 2′FL/LNnT. The gut microbiota composition, metabolite profiles and expression of genes related to host mucosal response were determined. Results: Moderate changes in fecal, but not mucosal, microbial composition (β-diversity) was observed during the intervention with higher dissimilarity observed within individuals receiving 10g 2′FL/LNnT compared to placebo. Both fecal and mucosal Bifidobacterium spp. increased after 2′FL/LNnT intake, with increased proportions of Bifidobacterium adolescentis and Bifidobacterium longum. Moreover, the intervention modulated the fecal and plasma metabolite profiles, but not the urine metabolite profile or the host mucosal response. Changes in the metabolite profiles were associated to changes in bifidobacteria abundance. Conclusion: Supplementation with 2′FL/LNnT modulated the gut microbiota, fecal and plasma metabolite profiles, but not the host mucosal response in IBS. Furthermore, the bifidogenic effect was associated with metabolite modulation. Overall, these findings support the assertion that 2′FL/LNnT supplementation modulate the intestinal microenvironment of patients with IBS, potentially related to health.

Physiological mechanisms of unexplained (functional) gastrointestinal disorders

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

Suppression of PTRF Alleviates Post-Infectious Irritable Bowel Syndrome via Downregulation of the TLR4 Pathway in Rats

Background: Accumulating evidence suggests that the polymerase I and transcript release factor (PTRF), a key component of the caveolae structure on the plasma membrane, plays a pivotal role in suppressing the progression of colorectal cancers. However, the role of PTRF in the development of functional gastrointestinal (GI) disorders remains unclear. Post-infectious irritable bowel syndrome (PI-IBS) is a common functional GI disorder that occurs after an acute GI infection. Here, we focused on the role of PTRF in the occurrence of PI-IBS and investigated the underlying mechanisms. Methods: Lipopolysaccharide (LPS) (5 μg/ml) was used to induce inflammatory injury in human primary colonic epithelial cells (HCoEpiCs). Furthermore, a rat model of PI-IBS was used to study the role of PTRF. Intestinal sensitivity was assessed based on the fecal water content. A two-bottle sucrose intake test was used to evaluate behavioral changes. Furthermore, shRNA-mediated knockdown of PTRF was performed both in vitro and in vivo. We detected the expression of PTRF in colonic mucosal tissues through immunohistochemistry (IHC), western blotting (WB), and immunofluorescence (IF) analysis. Luciferase activity was quantified using a luciferase assay. Co-localization of PTRF and Toll-like receptor 4 (TLR4) was detected using IF analysis. The activation of the signaling pathways downstream of TLR4, including the iNOs, p38, extracellular signal-regulated kinase (ERK), and c-Jun N-terminal kinase (JNK) pathways, was detected via WB. The levels of NO, IL-1β, IL-6, and TNF-α were measured using enzyme-linked immunosorbent assays. Results: LPS significantly induced PTRF expression and signaling downstream of TLR4, including p38, ERK, and JNK pathways, in HCoEpiCs. Moreover, shRNA-mediated knockdown of PTRF in HCoEpiCs significantly decreased the phosphorylation of JNK, ERK, and p38 and iNOS expression. In PI-IBS rats, the lack of PTRF not only reduced fecal water content and suppressed depressive behavior but also increased the body weight. Furthermore, we found a strong co-localization pattern for PTRF and TLR4. Consistently, the lack of PTRF impaired TLR4 signaling, as shown by the decreased levels of p-JNK, p-ERK, and p-p38, which are upstream factors involved in iNOS expression. Conclusion: PTRF promoted PI-IBS and stimulated TLR4 signaling both in vitro and in vivo. The results of this study not only enlighten the pathogenesis of PI-IBS but also help us understand the biological activity of PTRF and provide an important basis for the clinical treatment of PI-IBS by targeting PTRF.

A Distinct Faecal Microbiota and Metabolite Profile Linked to Bowel Habits in Patients with Irritable Bowel Syndrome

Patients with irritable bowel syndrome (IBS) are suggested to have an altered intestinal microenvironment. We therefore aimed to determine the intestinal microenvironment profile, based on faecal microbiota and metabolites, and the potential link to symptoms in IBS patients. The faecal microbiota was evaluated by the GA-map^TM dysbiosis test, and tandem mass spectrometry (GC-MS/MS) was used for faecal metabolomic profiling in patients with IBS and healthy subjects. Symptom severity was assessed using the IBS Severity Scoring System and anxiety and depression were assessed using the Hospital Anxiety and Depression Scale. A principal component analysis based on faecal microbiota (n = 54) and metabolites (n = 155) showed a clear separation between IBS patients (n = 40) and healthy subjects (n = 18). Metabolites were the main driver of this separation. Additionally, the intestinal microenvironment profile differed between IBS patients with constipation (n = 15) and diarrhoea (n = 11), while no clustering was detected in subgroups of patients according to symptom severity or anxiety. Furthermore, ingenuity pathway analysis predicted amino acid metabolism and several cellular and molecular functions to be altered in IBS patients. Patients with IBS have a distinct faecal microbiota and metabolite profile linked to bowel habits. Intestinal microenvironment profiling, based on faecal microbiota and metabolites, may be considered as a future non-invasive diagnostic tool, alongside providing valuable insights into the pathophysiology of IBS.

Identification of microbial markers across populations in early detection of colorectal cancer

Associations between gut microbiota and colorectal cancer (CRC) have been widely investigated. However, the replicable markers for early-stage adenoma diagnosis across multiple populations remain elusive. Here, we perform an integrated analysis on 1056 public fecal samples, to identify adenoma-associated microbial markers for early detection of CRC. After adjusting for potential confounders, Random Forest classifiers are constructed with 11 markers to discriminate adenoma from control (area under the ROC curve (AUC) = 0.80), and 26 markers to discriminate adenoma from CRC (AUC = 0.89), respectively. Moreover, we validate the classifiers in two independent cohorts achieving AUCs of 0.78 and 0.84, respectively. Functional analysis reveals that the altered microbiome is characterized with increased ADP-L-glycero-beta-D-manno-heptose biosynthesis in adenoma and elevated menaquinone-10 biosynthesis in CRC. These findings are validated in a newly-collected cohort of 43 samples using quantitative real-time PCR. This work proves the validity of adenoma-specific markers across multi-populations, which would contribute to the early diagnosis and treatment of CRC.

Changes of gut microbiome composition and metabolites associated with hypertensive heart failure rats

Background

The potential role of the gut microbiome (GM) in heart failure (HF) had recently been revealed. However, the underlying mechanisms of the GM and fecal metabolome in HF have not been characterized. The Dahl salt-sensitive rat model of hypertensive heart failure (H-HF) was used to study the clinical symptoms and characteristics. To elucidate the pathogenesis of HF, we combined 16S rRNA gene sequencing and metabolomics to analyze gut microbial compositions and fecal metabolomic profiles of rats with H-HF.

Results

PCoA of beta diversity shown that the gut microbiome composition profiles among the three groups were separated. Gut microbial composition was significantly altered in H-HF rats, the ratio of Firmicutes to Bacteroidetes(F/B) increased and the abundance of Muribaculaceae, Lachnospiraceae, and Lactobacillaceae decreased. Significantly altered levels of 17 genera and 35 metabolites were identified as the potential biomarker of H-HF. Correlation analysis revealed that specific altered genera were strongly correlated with changed fecal metabolites. The reduction in short-chain fatty acids (SCFA)-producing bacteria and trimethylamine N-oxide (TMAO) might be a notable characteristic for H-HF.

Conclusions

This is the first study to characterize the fecal microbiome of hypertensive heart failure by integrating 16S rRNA gene sequencing and LC–MS-based metabolomics approaches. Collectively, the results suggesting changes of gut microbiome composition and metabolites are associated with hypertensive heart failure rats.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12866-021-02202-5.

Metabarcoding analysis of gut microbiota of healthy individuals reveals impact of probiotic and maltodextrin consumption

In a previously published double-blind, placebo-controlled study, we showed that probiotics intake exerted a positive effect on sleep quality and a general improvement across time in different aspects of the profile of mood state, like sadness, anger, and fatigue in 33 healthy individuals. The present work investigates the impact of the probiotic product, constituted of Limosilactobacillus fermentum LF16, Lacticaseibacillus rhamnosus LR06, Lactiplantibacillus plantarum LP01 (all former members of Lactobacillus genus), and Bifidobacterium longum 04, on the gut microbiota composition of the same cohort through a metabarcoding analysis. Both the placebo and probiotic treatments had a significant impact on the microbiota composition. Statistical analysis showed that the microbiota of the individuals could be clustered into three groups, or bacteriotypes, at the baseline, and, inherently, bacterial compositions were linked to different responses to probiotic and placebo intakes. Interestingly, L. rhamnosus and L. fermentum were retrieved in the probiotic-treated cohort, while a bifidogenic effect of maltodextrin, used as placebo, was observed. The present study shed light on the importance of defining bacteriotypes to assess the impact of interventions on the gut microbiota and allowed to reveal microbial components which could be related to positive effects (i.e. sleep quality improvement) to be verified in further studies.

Altered metabolism of bile acids correlates with clinical parameters and the gut microbiota in patients with diarrhea-predominant irritable bowel syndrome

BACKGROUND

Bile acids (BAs) have attracted attention in the research of irritable bowel syndrome with predominant diarrhea (IBS-D) due to their ability to modulate bowel function and their tight connection with the gut microbiota. The composition of the fecal BA pool in IBS-D patients is reportedly different from that in healthy populations. We hypothesized that BAs may participate in the pathogenesis of IBS-D and the altered BA profile may be correlated with the gut microbiome.

AIM

To investigate the role of BAs in the pathogenesis of IBS-D and the correlation between fecal BAs and gut microbiota.

METHODS

Fifty-five IBS-D patients diagnosed according to the Rome IV criteria and twenty-eight age-, sex-, and body mass index-matched healthy controls (HCs) were enrolled in this study at the gastroenterology department of China-Japan Friendship Hospital. First, clinical manifestations were assessed with standardized questionnaires, and visceral sensitivity was evaluated via the rectal distension test using a high-resolution manometry system. Fecal primary BAs including cholic acid (CA) and chenodeoxycholic acid (CDCA), secondary BAs including deoxycholic acid (DCA), lithocholic acid (LCA), and ursodeoxycholic acid (UDCA) as well as the corresponding tauro- and glyco-BAs were examined by ultraperformance liquid chromatography coupled to tandem mass spectrometry. The gut microbiota was analyzed using 16S rRNA gene sequencing. Correlations between fecal BAs with clinical features and gut microbiota were explored.

RESULTS

Fecal CA (IBS-D: 3037.66 [282.82, 6917.47] nmol/g, HC: 20.19 [5.03, 1304.28] nmol/g; P < 0.001) and CDCA (IBS-D: 1721.86 [352.80, 2613.83] nmol/g, HC: 57.16 [13.76, 1639.92] nmol/g; P < 0.001) were significantly increased, while LCA (IBS-D: 1621.65 [58.99, 2396.49] nmol/g, HC: 2339.24 [1737.09, 2782.40]; P = 0.002] and UDCA (IBS-D: 8.92 [2.33, 23.93] nmol/g, HC: 17.21 [8.76, 33.48] nmol/g; P = 0.025) were significantly decreased in IBS-D patients compared to HCs. Defecation frequency was positively associated with CA (r = 0.294, P = 0.030) and CDCA (r = 0.290, P = 0.032) and negatively associated with DCA (r = -0.332, P = 0.013) and LCA (r = -0.326, P = 0.015) in IBS-D patients. In total, 23 of 55 IBS-D patients and 15 of 28 HCs participated in the visceral sensitivity test. The first sensation threshold was negatively correlated with CDCA (r = -0.459, P = 0.028) in IBS-D patients. Furthermore, the relative abundance of the family Ruminococcaceae was significantly decreased in IBS-D patients (P < 0.001), and 12 genera were significantly lower in IBS-D patients than in HCs (P < 0.05), with 6 belonging to Ruminococcaceae. Eleven of these genera were negatively correlated with primary BAs and positively correlated with secondary BAs in all subjects.

CONCLUSION

The altered metabolism of BAs in the gut of IBS-D patients was associated with diarrhea and visceral hypersensitivity and might be ascribed to dysbiosis, especially the reduction of genera in Ruminococcaceae.