Duodenal microbiota makes an important impact in functional dyspepsia

Microbial-derived peptidases are altered in celiac disease, non-celiac gluten sensitivity, and functional dyspepsia: a systematic review and re-analysis of the duodenal microbiome

Dietary gluten triggers symptoms in patients with gluten-related disorders (GRDs) including celiac disease (CeD), non-celiac gluten sensitivity (NCGS), and subsets of patients with functional dyspepsia (FD). The gastrointestinal microbiota is altered in these patients when compared to healthy individuals. As the microbiota is crucial for the hydrolysis of gluten, we hypothesized that the capacity of the microbiota to digest gluten is reduced in these conditions. We systematically reviewed and re-analyzed published datasets to compare gastrointestinal microbiomes of GRD patients and identify signals explaining gluten responses. A systematic search of five databases was conducted to identify studies where the microbiota of CeD, NCGS, or FD patients was analyzed by 16S rRNA amplicon or shotgun metagenomic sequencing and compared to control populations. Where available, raw duodenal microbiota sequence data were re-analyzed with a consistent bioinformatic pipeline. Thirty articles met the inclusion criteria for this systematic review. Microbiota diversity metrics were not impacted by the diseases; however, genera including Streptococcus, Neisseria, and Lactobacillus were commonly altered in GRD patients. Re-analysis of duodenal 16S rRNA data was possible for five included articles but did not identify any consistent differentially abundant taxa. Predicted functional analysis of the microbiome revealed that peptidases including aminopeptidase, proline iminopeptidase, and Xaa-Pro dipeptidase are altered in CeD, NCGS, and FD, respectively. These microbial-derived peptidases hydrolyze bonds in proline-rich gluten peptides. While the gastrointestinal microbiota in patients with GRDs differ from controls, no distinct phenotype links them. However, alterations to the predicted functional capacity of the microbiome to produce gluten-hydrolyzing enzymes suggest that inappropriate digestion of gluten by the microbiome impacts host responses to dietary gluten in these conditions. These findings have implications for therapeutic management of GRDs, as treatment with gluten-degrading enzymes or tailored probiotics could improve disease outcomes by enhancing gluten digestion into non-reactive peptides.

Therapeutic Role of Probiotics for the Treatment of Dyspepsia: A Review of the Literature

BACKGROUND

Dyspepsia is a common condition with a high prevalence in the general population. Patients in whom traditional diagnostic procedures can detect no identifiable explanation for the symptoms are diagnosed as being affected by functional dyspepsia (FD). To date, no etiological therapy for FD is available, and the current management includes general measures, acid-suppressive drugs, prokinetic agents, fundus-relaxing drugs, antidepressants, and psychological interventions. Recent evidence suggests that microbiota imbalance is involved in the development of FD. As a consequence, the modulation of microbiota through the use of probiotics could represent an effective therapeutic strategy. Moreover, Helicobacter pylori (HP) infection is a frequent cause of dyspepsia, and patients diagnosed with HP-associated dyspepsia are treated with HP eradication. In this regard, probiotics supplementation may also be helpful for HP infection to increase the eradication success rate as well as to reduce gastrointestinal adverse events caused by antibiotics.

PURPOSE

This review of the literature aims to summarize and discuss the current evidence on the use of probiotics in the treatment of dyspepsia and as a supplement to HP eradication therapy.

The Duodenal Microenvironment in Functional Dyspepsia

Functional dyspepsia (FD) is a chronic gastrointestinal disorder without a readily identifiable organic cause, resulting in bothersome upper abdominal symptoms. It is a highly prevalent disorder of which the pathophysiology remains mostly elusive, despite intensive research efforts. However, recent studies have found alterations in the microenvironment of the duodenum in patients with FD. In this review we summarize the duodenal microenvironment in homeostatic conditions and the alterations found in patients with FD, highlighting the similarities and discrepancies between different studies. The most consistent findings, being an impaired duodenal barrier and duodenal immune activation, are reviewed. We discuss the potential triggers for these observed alterations, including psychological comorbidities, luminal alterations and food related triggers. In summary, this review presents the evidence of molecular and cellular changes in patients with FD, with an impaired duodenal barrier and activated mucosal eosinophils and mast cells, challenging the notion that FD is purely functional, and offering different targets for potential future treatments.

Small intestinal microbiota: from taxonomic composition to metabolism

The small intestinal microbiota (SIM) is essential for gastrointestinal health, influencing digestion, immune modulation, and nutrient metabolism. Unlike the colonic microbiota, the SIM has been poorly characterized due to sampling challenges and ethical considerations. Current evidence suggests that the SIM consists of five core genera and additional segment-specific taxa. These bacteria closely interact with the human host, regulating nutrient absorption and metabolism. Recent work suggests the presence of two forms of small intestinal bacterial overgrowth, one dominated by oral bacteria (SIOBO) and a second dominated by coliform bacteria. Less invasive sampling techniques, omics approaches, and mechanistic studies will allow a more comprehensive understanding of the SIM, paving the way for interventions engineering the SIM towards better health.

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

Background and aims

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

Methods

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

Results

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

Conclusion

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

Pharmacokinetics and tissue distribution of four major bioactive components of Cynanchum auriculatum extract: a UPLC-MS/MS study in normal and functional dyspepsia rats

Introduction: Cynanchum auriculatum (CA) is usually used to treat digestive disorders, such as anorexia, enteritis, dysentery, and indigestion. Functional dyspepsia (FD) is characterized by a group of symptoms associated with the gastroduodenal region. Recent pharmacological studies have demonstrated the efficacy of CA for treating FD. However, the pharmacokinetics (PK) and tissue distribution of CA in physiological and FD states is still unclear. The present study aimed to clarify the differences in PK parameters and tissue distribution of the four major active components of CA (baishouwu benzophenone, deacylmet-aplexigenin, qingyangshengenin, and syringic acid) under both physiological and FD states. Methods: For this, normal and FD rats were orally administered 10 mg/kg CA extract. Then, plasma and tissue (heart, liver, spleen, lung, kidney, brain, stomach, and small intestine) samples were obtained. The four active components of CA in rat plasma and tissues were quantified by developing and validating a fast and reliable ultra-high-performance liquid chromatography-mass spectrometry method. Results: The area under the plasma concentration-time curve from time zero to time t (AUC0-t) of baishouwu benzophenone was significantly lower in the FD group than in the normal group (p < 0.01). The FD group had significantly lower (p < 0.001) apparent volume of distribution and plasma clearance of qing-yangshengenin and significantly higher (p < 0.05) AUC0-t of deacylmetaplexigenin and qingyangshengenin. The four active components were rapidly distributed into various tissues, and the main target organs of CA activity were the stomach and small intestine. In addition, baishouwu benzophenone, deacylmetaplexigenin, and qingyangshengenin could cross the blood-brain barrier, indicating that the brain may be another target organ in the treatment of FD. Discussion: These results indicate that the pathological state of FD alters the PK behavior and tissue distribution characteristics of baishouwu benzophenone, deacylmetaplexigenin, qingyangshengenin, and syringic acid in the CA extract, providing an experimental basis for the role of CA in FD treatment.

Progress in understanding of relationship between duodenal mucosal microecology and hepatitis B virus related acute-on-chronic liver failure

According to statistics, the rate of hepatitis B virus (HBV) infection is still high in China, and the mortality of acute-on-chronic liver failure (ACLF) is also high. In recent years, studies on the fecal flora of patients with HBV related ACLF have found that intestinal microecology affects the occurrence, development, and prognosis of HBV related ACLF. However, fecal flora cannot completely replace the whole intestinal microecology, and duodenal mucosal microecology may be a new research direction. This review discusses the influence of duodenal mucosal flora on the clinical outcome of HBV-ACLF with regard to mechanism, physiology, and anatomical characteristics.

Functional Gastrointestinal Disorders with Psychiatric Symptoms: Involvement of the Microbiome-Gut-Brain Axis in the Pathophysiology and Case Management

Functional Gastrointestinal Disorders have been an important cause of poor life quality in affected populations. The unclear etiology and pathophysiological mechanism alter the clinical evolution of the patient. Although a strong connection with psychological stress has been observed, it was not until recently that the gut-brain axis involvement has been revealed. Furthermore, the current literature not only promotes the gut-brain axis modulation as a therapeutical target for functional digestive disorders but also states that the gut microbiome has a main role in this bi-directional mechanism. Psychiatric symptoms are currently recognized as an equally important aspect of the clinical manifestation and modulation of both the digestive and central nervous systems and could be the best approach in restoring the balance. As such, this article proposes a detailed description of the physiology of the microbiome-gut-brain axis, the pathophysiology of the functional gastrointestinal disorders with psychiatric symptoms and current perspectives for therapeutical management, as revealed by the latest studies in the scientific literature.

Effects of Pb-, Cd-resistant bacterium Pantoea sp. on growth, heavy metal uptake and bacterial communities in oligotrophic growth substrates of Lolium multiflorum Lam

Phosphate-solubilizing bacteria (PSB) can accelerate phytoremediation, especially in those fertilized soils. However, PSB function in oligotrophic growth substrates remains poorly studied. In this study, we isolated lead (Pb)- and cadmium (Cd)-resistant PSB from contaminated sandy soil at an abandoned lubricant plant. The isolated Pantoea sp. PP4 (PP4 hereafter) can produce organic acid and IAA (Indole-3-acetic acid) and dissolve up to 238 mg/L of inorganic phosphate Ca2(PO4)3, exhibiting biosorption capability for Pb and bioprecipitation for Pb and Cd. In the sand pot experiment, inoculation of PP4 increased the accumulation of Pb and Cd in Lolium multiflorum Lam. by 28.9% and 95.5%, respectively, and increased the available phosphorous in oligotrophic river sand by 30.8% (P < 0.05). Meanwhile, the growth of Lolium multiflorum Lam. was also stimulated, resulting in 89.2%, 57.1%, 184.6%, and 28.5% increase in fresh weight, dry weight, root length, and shoot length, respectively. NMDS analysis showed that the bacterial communities in river sand were more clustered after inoculation with PP4. These results indicated that the application of Pantoea sp. PP4 can facilitate the phytoremediation of Pb and Cd in oligotrophic growth substrates, forming a convergent bacterial community. Our findings highlighted the importance of identifying ideal PSB to improve phytoremediation efficiency in oligotrophic environments.