Mode of action of Akkermansia muciniphila in the intestinal dialogue: role of extracellular proteins, metabolites and cell envelope components

Composition of Human-Associated Gut Microbiota Determines 3-DF and 3-HF Anti-Colitic Activity in IL-10 -/- Mice

BACKGROUND

Gut bacterial dysbiosis along with intestinal mucosal disruption plays a critical role in inflammatory disorders like ulcerative colitis. Flavonoids and other food bioactives have been studied in mice models as alternative treatments with minimal side effects. However, most of the research has been carried out with mice-native microbiota, which limits the comprehension of the interaction between flavonoids and human-associated bacteria. Hence, the objective of our study was to determine the effect of healthy human-associated microbiota on the anti-colitic activity of diets rich in anthocyanins (3-HF) and phlobaphenes (3-DF).

METHODS

In this regard, the interleukin (IL)-10 -/- mice model was utilized. Mice were divided into three groups for inoculation with human gut bacteria from three different healthy donors and assigned to four diets. A purified diet (Diet P) and three diets containing 25% near-isogenic lines (NILs) of corn were evaluated. Diets were substituted with NILs expressing only 3-DFs (diet B), only 3-HFs (diet C), and both 3-DF and 3-HF (diet D).

RESULTS

In an overall analysis, flavonoid-rich diets did not affect inflammatory markers, microbiota diversity, or gut metabolites, but diets containing anthocyanins improved barrier function parameters. However, when data was segmented by the recipient's microbiota from different human donors, the diet effects became significant. Furthermore, 3-HFs showed more beneficial effects than 3-DFs across the recipient's microbiota.

CONCLUSIONS

Our study suggests that the anti-colitic activity of 3-DF and 3-HF and their gut metabolites depends on the donor's microbial composition.

Oral supplementation with lactic acid bacteria improve the intestinal epithelial barrier and gut microbiota of broiler chicks to alleviate Salmonella Enteritidis infection

Lactic acid bacteria (LAB) play a key role in regulating the balance of gut microbiota and serve as a suitable alternative to antibiotics. This study aims to evaluate the characteristics of 2 LAB isolates Lactiplantibacillus plantarum Lp71 (L. plantarum Lp71) and Enterococcus faecium Ef72 (E. faecium Ef72), and their roles in alleviating Salmonella Enteritidis infection. Sixty 1-day-old chicks were randomly divided into 4 groups which treated with or without L. plantarum Lp71 and E. faecium Ef72 mixture for 21 d, and then intestinal samples were collected for gut microbiota analysis, pathological and immunohistochemical analysis at 24 h post infection with or without Salmonella Enteritidis on the 22nd d. The results showed that L. plantarum Lp71 and E. faecium Ef72 had the ability to anti-acid and anti-bile salt. Salmonella Enteritidis infection damaged the intestinal epithelial barrier and reduced the expression level of tight junction proteins (ZO-1, Claudin-1, Occludin). Oral supplementation with L. plantarum Lp71 and E. faecium Ef72 mixture could alleviated the damages to intestinal epithelial barrier by Salmonella Enteritidis infection. Salmonella Enteritidis could cause abnormal Akkermansia muciniphila proliferation and decrease the diversity of cecal microbiota in chicks. These conditions could have further led to reduce gut microbiota health index (GMHI), and improve microbial dysbiosis index (MDI). Moreover, oral supplementation with L. plantarum Lp71 and E. faecium Ef72 mixture could effectively prevent the aforementioned infection outcomes and increase the abundance proportions of the several key functions in metabolic pathways metabolic pathways such as transcription and signal transduction mechanisms. In summary, L. plantarum Lp71 and E. faecium Ef72 could be the probiotics candidates that used to prevent the damage from enteric pathogens such as Salmonella Enteritidis in broiler chicks.

Efficacy of ETB-F01, Heat-Killed Akkermansia muciniphila Strain EB-AMDK19, in Patients with Respiratory Symptoms: A Multicenter Clinical Trial

Respiratory symptoms are prevalent in the general population, and they are associated with a decline in lung function and increased mortality. The gut-lung connection suggests intestinal dysbiosis may impact lung diseases, with Akkermansia muciniphila showing promise in regulating extraintestinal diseases. However, its application in patients with respiratory symptoms lacks clinical trial evidence. In this randomized, double-blind trial, ETB-F01, containing heat-killed A. muciniphila strain EB-AMDK19, was compared with a placebo in patients experiencing respiratory symptoms for 4 to 12 weeks. The primary outcome was improvement in Breathlessness, Cough, and Sputum Scale (BCSS) score over 12 weeks. Secondary outcomes included lung function, fractional exhaled nitric oxide (FeNO), modified Medical Research Council (mMRC) dyspnea scale, St. George's Respiratory Questionnaire (SGRQ), and Visual Analog Scale (VAS) score. The primary analysis was performed in the per-protocol set, with a sensitivity analysis in the full analysis set. In the per-protocol population, 68 participants were randomly assigned to the ETB-F01 group and 65 to the placebo group. ETB-F01 had a superior efficacy over placebo in improving BCSS total scores (between-group difference = -0.8 (95% confidence interval, -1.4--0.3), p-value = 0.004). Specifically, there was a significant reduction in BCSS breathlessness and cough domain scores with ETB-F01. While trends toward improvement in lung function were noted, statistical significance was not achieved. No significant differences were observed in FeNO and other symptom scores (mMRC, SGRQ, and VAS). In safety profile, ETB-F01 did not cause any serious adverse events. These results suggest that ETB-F01 is safe and effective for alleviating respiratory symptoms.

A comprehensive update on the immunoregulatory mechanisms of Akkermansia muciniphila: insights into active ingredients, metabolites, and nutrient-driven modulation

Akkermansia muciniphila (A. muciniphila) has gained recognition as a pioneering probiotic, exhibiting considerable potential to enhance immune conditions across both humans and animals. The health benefits of A. muciniphila are attributed to its various components, including outer membrane proteins (PilQ and Amuc_1100), secreted proteins (P9 and AmTARS), extracellular vesicles, and metabolites such as SCFAs, ornithine lipids, γ-aminobutyric acid, cobalamin, and inosine. The dynamic control of the mucus layer by A. muciniphila plays a crucial role in regulating intestinal mucosal immunity. Furthermore, A. muciniphila modulates immune function by interacting with macrophages, dendritic cells, T lymphocytes, and Paneth cells. Increasing the abundance of A. muciniphila in the gut through nutritional strategies represents a safe and effective means to augment immune function. Various polyphenols, oligosaccharides, and polysaccharides have been shown to elevate the levels of this bacterium, thereby contributing to favorable immunoregulatory outcomes. This paper delves into the latest research advancements related to the probiotic mechanisms of A. muciniphila and provides an overview of the current understanding of how its abundance responds to nutrients. These insights offer a theoretical foundation for the utilization of A. muciniphila in immunoregulation.

Gut microbiota and their relationship with circulating adipokines in an acute hepatic encephalopathy mouse model induced by surgical bile duct ligation

Background and aims

Various studies have shown the importance of the gut microbiota in human health. However, little is known about gut microbiome patterns and their effect on circulating adipo-myokine levels in hepatic encephalopathy (HE). We investigated the relationship between the gut microbiota and adipo-myokine levels using a mouse model of HE induced by surgical bile duct ligation (BDL).

Methods and results

Wild-type C57BL/6J mice were subjected to sham surgery or BDL. Severe body weight loss, suppressed feed intake, and liver failure were observed in BDL mice compared with sham control mice. Additionally, changes in gut microbial communities and serum adipo-myokine levels were noted in BDL mice. In the BDL mouse gut, we identified 15 differentially abundant taxa including the phylum Verrucomicrobiota, the classes Actinomycetes and Verrucomicrobiae, the order Verrucomicrobiales, the families Akkermansiaceae, Bacteroidaceae, Rikenellaceae, and Oscillospiraceae, the genera Alistipes, Akkermansia, Muribaculum, and Phocaeicola, and the species Akkermansia muciniphila, Alistipes okayasuensis, and Muribaculum gordoncarteri by LEfSe analysis (LDA score≥4.0). Higher levels of certain adipo-myokines such as BDNF were detected in the serum of BDL mice. Spearman correlation analysis revealed that certain adipo-myokines (e.g., FSTL1) were positively correlated with the class Actinomycetes, the family Rikenellaceae, the genus Alistipes, and the species Alistipes okayasuensis. Interestingly, A. okayasuensis and M. gordoncarteri, recently isolated microbes, showed richness in the gut of BDL mice and demonstrated positive correlations with adipo-myokines such as FGF21.

Conclusions

Overall, our results suggest that alteration of the gut microbiota in patients with HE may be closely correlated to the levels of adipo-myokines in the blood.

What defines a healthy gut microbiome?

The understanding that changes in microbiome composition can influence chronic human diseases and the efficiency of therapies has driven efforts to develop microbiota-centred therapies such as first and next generation probiotics, prebiotics and postbiotics, microbiota editing and faecal microbiota transplantation. Central to microbiome research is understanding how disease impacts microbiome composition and vice versa, yet there is a problematic issue with the term 'dysbiosis', which broadly links microbial imbalances to various chronic illnesses without precision or definition. Another significant issue in microbiome discussions is defining 'healthy individuals' to ascertain what characterises a healthy microbiome. This involves questioning who represents the healthiest segment of our population-whether it is those free from illnesses, athletes at peak performance, individuals living healthily through regular exercise and good nutrition or even elderly adults or centenarians who have been tested by time and achieved remarkable healthy longevity.This review advocates for delineating 'what defines a healthy microbiome?' by considering a broader range of factors related to human health and environmental influences on the microbiota. A healthy microbiome is undoubtedly linked to gut health. Nevertheless, it is very difficult to pinpoint a universally accepted definition of 'gut health' due to the complexities of measuring gut functionality besides the microbiota composition. We must take into account individual variabilities, the influence of diet, lifestyle, host and environmental factors. Moreover, the challenge in distinguishing causation from correlation between gut microbiome and overall health is presented.The review also highlights the resource-heavy nature of comprehensive gut health assessments, which hinders their practicality and broad application. Finally, we call for continued research and a nuanced approach to better understand the intricate and evolving concept of gut health, emphasising the need for more precise and inclusive definitions and methodologies in studying the microbiome.

The Modulatory Effects and Therapeutic Potential of Cannabidiol in the Gut

Cannabidiol (CBD) is a major non-psychotropic phytocannabinoid that exists in the Cannabis sativa plant. CBD has been found to act on various receptors, including both cannabinoid and non-cannabinoid receptors. In addition, CBD has antioxidant effects that are independent of receptors. CBD has demonstrated modulatory effects at different organ systems, such as the central nervous system, immune system, and the gastrointestinal system. Due to its broad effects within the body and its safety profile, CBD has become a topic of therapeutic interest. This literature review summarizes previous research findings with regard to the effect of CBD on the gastrointestinal (GI) system, including its effects at the molecular, cellular, organ, and whole-body levels. Both pre-clinical animal studies and human clinical trials are reviewed. The results of the studies included in this literature review suggest that CBD has significant impact on intestinal permeability, the microbiome, immune cells and cytokines. As a result, CBD has been shown to have therapeutic potential for GI disorders such as inflammatory bowel disease (IBD). Furthermore, through interactions with the gut, CBD may also be helpful in the treatment of disorders outside the GI system, such as non-alcoholic liver disease, postmenopausal disorders, epilepsy, and multiple sclerosis. In the future, more mechanistic studies are warranted to elucidate the detailed mechanisms of action of CBD in the gut. In addition, more well-designed clinical trials are needed to explore the full therapeutic potential of CBD on and through the gut.

Possible application of Akkermansia muciniphila in stress management

Akkermansia muciniphila (A. muciniphila) is a promising candidate bacterium for stress management due to its beneficial effects on the microbiota-gut-brain axis (MGBA). As a well-known mucin-degrading bacterium in the digestive tract, A. muciniphila has demonstrated significant benefits for host physiology. Recent research highlights its potential in treating several neuropsychiatric disorders. Proposed mechanisms of action include the bacterium's outer membrane protein Amuc_1100 and potentially its extracellular vesicles (EVs), which interact with host immune receptors and influence serotonin pathways, which are crucial for emotional regulation. Despite its potential, the administration of probiotics containing A. muciniphila faces technological challenges, prompting the development of pasteurized forms recognized as safe by the European Food Safety Authority (EFSA). This review systematically examines the existing literature on the role of A. muciniphila in stress management, emphasizing the need for further research to validate its efficacy. The review follows a structured methodology, including comprehensive database searches and thematic data analysis, to provide a detailed understanding of the relationship between stress, microbiota, and A. muciniphila therapeutic potential.

The biofunction of Akkermansia muciniphila in intestinal-related diseases

Intestinal homeostasis is essential for maintaining human health, and its dysfunction is related to the onset and progression of various diseases, including immune and metabolic disorders, and even tumorigenesis. Intestinal microbiota plays a critical role in intestinal homeostasis, with Akkermansia muciniphila (A. muciniphila) emerging as a key commensal bacterium utilizing mucin as its sole carbon and nitrogen source. A. muciniphila has been recognized in both experimental and clinical studies for its beneficial role in managing intestinal inflammation, tumors, functional gastrointestinal disorders, and secondary conditions such as liver and metabolic diseases. This review provides a comprehensive overview of the research history and current understanding of A. muciniphila, its association with various intestinal-related diseases, and the potential mechanisms behind its effects. This paper also explores the possibilities of leveraging the probiotic enzyme such as the active ingredients of A. muciniphila for the innovative clinical treatment of intestinal-related diseases.

The Human Microbiome as a Therapeutic Target for Metabolic Diseases

The human microbiome functions as a separate organ in a symbiotic relationship with the host. Disruption of this host-microbe symbiosis can lead to serious health problems. Modifications to the composition and function of the microbiome have been linked to changes in host metabolic outcomes. Industrial lifestyles with high consumption of processed foods, alcoholic beverages and antibiotic use have significantly altered the gut microbiome in unfavorable ways. Therefore, understanding the causal relationship between the human microbiome and host metabolism will provide important insights into how we can better intervene in metabolic health. In this review, I will discuss the potential use of the human microbiome as a therapeutic target to improve host metabolism.

Omics-based analysis of Akkermansia muciniphila cultivation in food-grade media

Background and Aim: Over the past years, the gut microbiota and its correlation to health and disease has been studied extensively. In terms of beneficial microbes, an increased interest in Akkermansia muciniphila (A. muciniphila) has been observed since its discovery. Direct evidence for the role of A. muciniphila in host health has been provided in both mice and human studies. However, for human interventions with A. muciniphila cells, industrial-scale fermentations are needed, and hence, the used cultivation media should be free of animal-derived components, food-grade, non-allergenic and allow for efficient growth to high densities to provide cost-effective production platforms. In this study, we assessed the growth and performance of A. muciniphila in batch bioreactors using newly developed plant-based media. Methods: The bioreactors were supplemented with varying carbon sources, including different ratios of N-acetylglucosamine (GlcNAc) and glucose. We monitored the growth of A. muciniphila in the plant-based medium using optical density (OD600) measurements and microscopy. In addition, we used a combination of biochemical analysis as well as transcriptional and proteomics analysis to gain detailed insight into the physiology. Results: Comparisons between growth on these media and that on mucin revealed differences at both transcriptome and proteome levels, including differences in the expression of glycosyltransferases, signaling proteins, and stress response. Furthermore, elongated cells and higher OD600 values were observed using the plant-based media as compared to cultivation media containing mucin. Conclusion: These differences do not hamper growth, and therefore, our data suggest that the food-grade medium composition described here could be used to produce A. muciniphila with high yields for therapeutic purposes.

Insights into the Mechanisms of Action of Akkermansia muciniphila in the Treatment of Non-Communicable Diseases

This comprehensive review delineates the extensive roles of Akkermansia muciniphila in various health domains, spanning from metabolic and inflammatory diseases to neurodegenerative disorders. A. muciniphila, known for its ability to reside in the mucous layer of the intestine, plays a pivotal role in maintaining gut integrity and interacting with host metabolic processes. Its influence extends to modulating immune responses and potentially easing symptoms across several non-communicable diseases, including obesity, diabetes, inflammatory bowel disease, and cancer. Recent studies highlight its capacity to interact with the gut-brain axis, suggesting a possible impact on neuropsychiatric conditions. Despite the promising therapeutic potential of A. muciniphila highlighted in animal and preliminary human studies, challenges remain in its practical application due to stability and cultivation issues. However, the development of pasteurized forms and synthetic mediums offers new avenues for its use in clinical settings, as recognized by regulatory bodies like the European Food Safety Authority. This narrative review serves as a crucial resource for understanding the broad implications of A. muciniphila across different health conditions and its potential integration into therapeutic strategies.

The secreted protein Amuc_1409 from Akkermansia muciniphila improves gut health through intestinal stem cell regulation

Akkermansia muciniphila has received great attention because of its beneficial roles in gut health by regulating gut immunity, promoting intestinal epithelial development, and improving barrier integrity. However, A. muciniphila-derived functional molecules regulating gut health are not well understood. Microbiome-secreted proteins act as key arbitrators of host-microbiome crosstalk through interactions with host cells in the gut and are important for understanding host-microbiome relationships. Herein, we report the biological function of Amuc_1409, a previously uncharacterised A. muciniphila-secreted protein. Amuc_1409 increased intestinal stem cell (ISC) proliferation and regeneration in ex vivo intestinal organoids and in vivo models of radiation- or chemotherapeutic drug-induced intestinal injury and natural aging with male mice. Mechanistically, Amuc_1409 promoted E-cadherin/β-catenin complex dissociation via interaction with E-cadherin, resulting in the activation of Wnt/β-catenin signaling. Our results demonstrate that Amuc_1409 plays a crucial role in intestinal homeostasis by regulating ISC activity in an E-cadherin-dependent manner and is a promising biomolecule for improving and maintaining gut health.

Physiology of γ-aminobutyric acid production by Akkermansia muciniphila

Gut bacteria hold the potential to produce a broad range of metabolites that can modulate human functions, including molecules with neuroactive potential. One such molecule is γ-aminobutyric acid (GABA), the main inhibitory neurotransmitter of the central nervous system in animals. Metagenomic analyses suggest that the genomes of many gut bacteria encode glutamate decarboxylase (GAD), the enzyme that catalyzes GABA production. The genome of Akkermansia muciniphila, a mucin specialist and potential next-generation probiotic from the human gut, is predicted to encode GAD, suggesting a contributing role in GABA production in the human gut. In this study, A. muciniphila was grown in batch cultures with and without pH control. In both experiments, A. muciniphila was found to produce GABA as a response to acid (pH <5.5), although only when GABA precursors, either glutamate or glutamine, were present in the medium. Proteomic analysis comparing A. muciniphila grown with and without precursors at pH 4 did not show a difference in GAD expression, suggesting that it is expressed regardless of the presence of GABA precursors. To further investigate the function of A. muciniphila GAD, we heterologously expressed the gad gene (encoded by locus tag Amuc_0372) with a His tag in Escherichia coli and purified the GAD protein. Enzyme assays showed GAD activity in a pH range between 4 and 6, with the highest specific activity at pH 5 of 144 ± 16 µM GABA/min/mg. Overall, our results demonstrate the ability of A. muciniphila to produce GABA as an acid response and unravel the conditions under which GABA production in A. muciniphila occurs.IMPORTANCEAkkermansia muciniphila is considered to be a beneficial bacterium from the human gut, but the exact mechanisms by which A. muciniphila influences its host are not yet fully understood. To this end, it is important to identify which metabolites are produced and consumed by A. muciniphila that may contribute to a healthy gut. In the present study, we demonstrate the ability of A. muciniphila to produce γ-aminobutyric acid (GABA) when grown in an acidic environment, which often occurs in the gut. GABA is the major inhibitory neurotransmitter in the central nervous system and is present in the human gut. For this reason, it is considered an important bacterial metabolite. Our finding that A. muciniphila produces GABA in acidic environments adds to the growing body of understanding of its relationship with host health and provides an explanation on how it can survive acid stress in the human gut.

Pasteurized Akkermansia muciniphila improves glucose metabolism is linked with increased hypothalamic nitric oxide release

Background and objective

Pasteurized Akkermansia muciniphila cells have shown anti-diabetic effects in rodents and human. Although, its primary site of action consists in maintaining the gut barrier function, there are no study exploring if A. muciniphila controls glycemia via a gut to brain axis. Targeting the gut motility represents an alternative pathway to treat hyperglycemia. Here, we tested the impact of pasteurized A. muciniphila on gut motility, gut-brain axis and glucose metabolism.

Methods

We used mice fed a 45% high-fat (HFD) treated or not with pasteurized A. muciniphila Muc^T during 12 weeks. We measured the effects of the treatment on body weight gain, glucose metabolism (insulin, glycemia, glucose tolerance), gut contraction and enteric neurotransmitter release, and hypothalamic nitric oxide (NO) release.

Results

We show that pasteurized A. muciniphila exerts positive effects on different metabolic parameters such as body weight, fat mass, insulin, glycemia and glucose tolerance. This could be explained by the ability of pasteurized A. muciniphila supplementation to decrease duodenal contraction and to increase hypothalamic NO release in HFD mice.

Conclusion

We demonstrate a novel mode of action of pasteurized A. muciniphila explaining its beneficial impact on the control of glycemia in a preclinical model of type 2 diabetes via gut-brain axis signaling.