The genome of Akkermansia muciniphila, a dedicated intestinal mucin degrader, and its use in exploring intestinal metagenomes

Akkermansia muciniphila: A promising probiotic against inflammation and metabolic disorders

Metabolic disease is a worldwide epidemic that has become a public health problem. Gut microbiota is considered to be one of the important factors that maintain human health by regulating host metabolism. As an abundant bacterium in the host gut, A. muciniphila regulates metabolic and immune functions, and protects gut health. Multiple studies have indicated that alterations in the abundance of A. muciniphila are associated with various diseases, including intestinal inflammatory diseases, obesity, type 2 diabetes mellitus, and even parasitic diseases. Beneficial effects were observed not only in live A. muciniphila, but also in pasteurized A. muciniphila, A. muciniphila-derived extracellular vesicles, outer membrane, and secreted proteins. Although numerous studies have only proven the simple correlation between multiple diseases and A. muciniphila, an increasing number of studies in animal models and preclinical models have demonstrated that the beneficial impacts shifted from correlations to in-depth mechanisms. In this review, we provide a comprehensive view of the beneficial effects of A. muciniphila on different diseases and summarize the potential mechanisms of action of A. muciniphila in the treatment of diseases. We provide a comprehensive understanding of A. muciniphila for improving host health and discuss the perspectives of A. muciniphila in the future studies.

A Critical Review on Akkermansia muciniphila: Functional Mechanisms, Technological Challenges, and Safety Issues

Due to its physiological benefits from in vitro and in vivo points of view, Akkermansia muciniphila, a common colonizer in the human gut mucous layer, has consistently been identified as an option for the next-generation probiotic. A. muciniphila is a significant bacterium that promotes host physiology. However, it also has a great deal of potential to become a probiotic due to its physiological advantages in a variety of therapeutic circumstances. Therefore, it can be established that the abundance of A. muciniphila in the gut environment, which is controlled by many genetic and dietary variables, is related to the biological behaviors of the intestinal microbiota and gut dysbiosis/eubiosis circumstances. Before A. muciniphila is widely utilized as a next-generation probiotic, regulatory obstacles, the necessity for significant clinical trials, and the sustainability of manufacturing must be eliminated. In this review, the outcomes of recent experimental and clinical reports are comprehensively reviewed, and common colonization patterns, main factors involved in the colonization of A. muciniphila in the gut milieu, their functional mechanisms in establishing homeostasis in the metabolic and energy pathways, the promising delivery role of microencapsulation, potential genetic engineering strategies, and eventually safety issues of A. muciniphila have been discussed.

Genome- and Toxicology-Based Safety Assessment of Probiotic Akkermansia muciniphila ONE Isolated from Humans

In this study, the genome of Akkermansia muciniphila ONE (designated AKK ONE) was sequenced, assembled, and analyzed. In addition, the safety of this strain was further evaluated by toxicological studies. The results showed that the AKK ONE genome is contained on a single chromosome with a total length of 2,817,524 bp and an average GC content of 55.48%. In total, 2411, 1131, 1168, 1745, and 1402 genes were annotated to the NR, GO, KEGG, COG, and SwissProt database, respectively. Potential resistance genes, adeF, tetW, ANT(3″)-IIa, and aadA1 were detected. AKK ONE was sensitive to ampicillin, ceftriaxone, cefotaxime, meropenem, tetracycline, and chloramphenicol and resistant to moxifloxacin. No potential virulence-related genes were detected. The PathogenFinder database analysis showed that AKK ONE was a non-potential human pathogen. This strain had good gastroenteric fluid tolerance and a weak ability to colonize the gut. No test item-related adverse effects were observed in the acute and subchronic toxicity test. AKK ONE did not display mutagenic activity either. This strain did not change the hematological and clinical biochemical parameters of mice. The weights of the organs were not affected by AKK ONE treatment. These results support that AKK ONE is safe for use as a probiotic at a dose of 8.28 × 109 CFU/kg bw/day.

Binding of Akkermansia muciniphila to mucin is O-glycan specific

The intestinal anaerobic bacterium Akkermansia muciniphila is specialized in the degradation of mucins, which are heavily O-glycosylated proteins that constitute the major components of the mucus lining the intestine. Despite that adhesion to mucins is considered critical for the persistence of A. muciniphila in the human intestinal tract, our knowledge of how this intestinal symbiont recognizes and binds to mucins is still limited. Here, we first show that the mucin-binding properties of A. muciniphila are independent of environmental oxygen concentrations and not abolished by pasteurization. We then dissected the mucin-binding properties of pasteurized A. muciniphila by use of a recently developed cell-based mucin array that enables display of the tandem repeats of human mucins with distinct O-glycan patterns and structures. We found that A. muciniphila recognizes the unsialylated LacNAc (Galβ1-4GlcNAcβ1-R) disaccharide selectively on core2 and core3 O-glycans. This disaccharide epitope is abundantly found on human colonic mucins capped by sialic acids, and we demonstrated that endogenous A. muciniphila neuraminidase activity can uncover the epitope and promote binding. In summary, our study provides insights into the mucin-binding properties important for colonization of a key mucin-foraging bacterium.

Implications of Artificial Intelligence in Addressing Antimicrobial Resistance: Innovations, Global Challenges, and Healthcare's Future

Antibiotic resistance poses a significant threat to global public health due to complex interactions between bacterial genetic factors and external influences such as antibiotic misuse. Artificial intelligence (AI) offers innovative strategies to address this crisis. For example, AI can analyze genomic data to detect resistance markers early on, enabling early interventions. In addition, AI-powered decision support systems can optimize antibiotic use by recommending the most effective treatments based on patient data and local resistance patterns. AI can accelerate drug discovery by predicting the efficacy of new compounds and identifying potential antibacterial agents. Although progress has been made, challenges persist, including data quality, model interpretability, and real-world implementation. A multidisciplinary approach that integrates AI with other emerging technologies, such as synthetic biology and nanomedicine, could pave the way for effective prevention and mitigation of antimicrobial resistance, preserving the efficacy of antibiotics for future generations.

Bifidobacterium pseudocatenulatum In Vitro In Vivo

The genus Bifidobacterium has been widely used in functional foods for health promotion due to its beneficial effects on human health, especially in the gastrointestinal tract (GIT). In this study, we characterize the anti-inflammatory potential of the probiotic strain Bifidobacterium pseudocatenulatum G7, isolated from a healthy male adult. G7 secretion inhibited inflammatory response in lipopolysaccharide (LPS)-stimulated RAW 264.7 macrophages. Moreover, oral administration of bacteria G7 alleviated the severity of colonic inflammation in dextran sulfate sodium (DSS)-treated colitis mice, which was evidenced by a decreased disease activity index (DAI) and enhanced structural integrity of the colon. The 16S rRNA gene sequencing result illustrated that the G7 alleviated DSS-induced gut microbiota dysbiosis, accompanied by the modulated bile acids and short-chain fatty acid (SCFA) levels. Overall, our results demonstrated the potential anti-inflammatory effects of Bifidobacterium pseudocatenulatum G7 on both in vitro and in vivo models, which provided a solid foundation for further development of a novel anti-inflammatory probiotic.

Optimizing Akkermansia muciniphila Isolation and Cultivation: Insights into Gut Microbiota Composition and Potential Growth Promoters in a Chinese Cohort

The study aims to analyze the composition of the gut microbiota in Chinese individuals using metagenomic sequencing technology, with a particular focus on the abundance of Akkermansia muciniphila (Akk). To improve the efficiency of Akk isolation and identification accuracy, modifications were made to the enrichment culture medium and 16S rRNA universal primers. Additionally, potential growth-promoting factors that stimulate Akk growth were explored through in vitro screening. The research results revealed that the abundance of Akk in Chinese fecal samples ranged from 0.004% to 0.4%. During optimization, a type of animal protein peptide significantly enhanced the enrichment efficiency of Akk, resulting in the isolation of three Akk strains from 14 fecal samples. Furthermore, 17 different growth-promoting factors were compared, and four factors, including galactose, sialic acid, lactose, and chitosan, were identified as significantly promoting Akk growth. Through orthogonal experiments, the optimal ratio of these four growth-promoting factors was determined to be 1:1:2:1. After adding 1.25% of this growth-promoting factor combination to the standard culture medium, Akk was cultivated at 37° for 36 h, achieving an OD600nm value of 1.169, thus realizing efficient proliferation and optimized cultivation of Akk. This study provides important clues for a deeper understanding of the gut microbiota composition in Chinese individuals, while also offering effective methods for the isolation and cultivation of Akk, laying the groundwork for its functional and application research in the human body.

Gut dysbiosis was inevitable, but tolerance was not: temporal responses of the murine microbiota that maintain its capacity for butyrate production correlate with sustained antinociception to chronic voluntary morphine

The therapeutic benefits of opioids are compromised by the development of analgesic tolerance, which necessitates higher dosing for pain management thereby increasing the liability for dependence and addiction. Rodent models indicate opposing roles of the gut microbiota in tolerance: morphine-induced gut dysbiosis exacerbates tolerance, whereas probiotics ameliorate tolerance. Not all individuals develop tolerance which could be influenced by differences in microbiota, and yet no study has capitalized upon this natural variation to identify specific features linked to tolerance. We leveraged this natural variation in a murine model of voluntary oral morphine self-administration to elucidate the mechanisms by which microbiota influences tolerance. Although all mice shared similar and predictive morphine-driven microbiota changes that largely masked informative associations with variability in tolerance, our high-resolution temporal analyses revealed a divergence in the progression of dysbiosis that best explained differences in the development in tolerance. Mice that did not develop tolerance also maintained a higher abundance of taxa capable of producing the short-chain fatty acid (SCFA) butyrate, known to bolster intestinal barriers, suppress inflammation, and promote neuronal homeostasis. Furthermore, dietary butyrate supplementation significantly reduced the development of tolerance. These findings could inform immediate therapies to extend the analgesic efficacy of opioids.

The role of Akkermansia muciniphila in colorectal cancer: A double-edged sword of treatment or disease progression?

Colorectal cancer (CRC) is the second most cancer-related death worldwide. In recent years, probiotics have been used to reduce the potential risks of CRC and tumors with various mechanisms. Different bacteria have been suggested to play different roles in the progression, prevention, or treatment of CRC. Akkermansia muciniphila is considered a next-generation probiotic for preventing and treating some diseases. Therefore, in this review article, we aimed to describe and discuss different mechanisms of A. muciniphila as an intestinal microbiota or probiotic in CRC. Some studies suggested that the abundance of A. muciniphila was higher or increased in CRC patients compared to healthy individuals. However, the decreased abundance of A. muciniphila was associated with severe symptoms of CRC, indicating that A. muciniphila did not play a role in the development of CRC. In addition, A. muciniphila administration elevates gene expression of proliferation-associated molecules such as S100A9, Dbf4, and Snrpd1, or markers for cell proliferation. Some other studies suggested that inflammation and tumorigenesis in the intestine might promoted by A. muciniphila. Overall, the role of A. muciniphila in CRC development or inhibition is still unclear and controversial. Various methods of bacterial supplementation, such as viability, bacterial number, and abundance, could all influence the colonization effect of A. muciniphila administration and CRC progression. Overall, A. mucinipila has been revealed to modulate the therapeutic potential of immune checkpoint inhibitors. Preliminary human data propose that oral consumption of A. muciniphila is safe, but its efficacy needs to be confirmed in more human clinical studies.

Akkermansia muciniphila: a potential candidate for ameliorating metabolic diseases

Metabolic diseases are comprehensive disease based on obesity. Numerous cumulative studies have shown a certain correlation between the fluctuating abundance of Akkermansia muciniphila and the occurrence of metabolic diseases. A. muciniphila, a potential probiotic candidate colonized in the human intestinal mucus layer, and its derivatives have various physiological functions, including treating metabolic disorders and maintaining human health. This review systematically explicates the abundance change rules of A. muciniphila in metabolic diseases. It also details the high efficacy and specific molecules mechanism of A. muciniphila and its derivatives in treating obesity, type 2 diabetes mellitus, cardiovascular disease, and non-alcoholic fatty liver disease.

Immune system and gut microbiota senescence in elderly IBD patients

In inflammatory bowel disease (IBD), the loss of immune tolerance against gut microbiota causes chronic inflammation and the progressive accumulation of organ damage in genetically susceptible individuals. In the elderly, IBD is often characterized by a different disease behavior when compared with pediatric and young adult disease. Besides disease behavior, another aspect of the multifaceted impact of age on elderly IBD course is increased susceptibility to infections. In this context, age-of-onset-dependent IBD behavior and clinical course are two major contributors to immune system senescence and change of gut microbiota in older subjects. Here, we review the available literature linking immunosenescence and age-dependent changes in the gut microbiota composition to IBD pathogenesis speculating on their possible implications in disease expression in this age class.

A Dual Therapeutic Approach to Diabetes Mellitus via Bioactive Phytochemicals Found in a Poly Herbal Extract by Restoration of Favorable Gut Flora and Related Short-Chain Fatty Acids

Diabetes mellitus (DM), a metabolic and endocrine condition, poses a serious threat to human health and longevity. The emerging role of gut microbiome associated with bioactive compounds has recently created a new hope for DM treatment. UHPLC-HRMS methods were used to identify these compounds in a poly herbal ethanolic extract (PHE). The effects of PHE on body weight (BW), fasting blood glucose (FBG) level, gut microbiota, fecal short-chain fatty acids (SCFAs) production, and the correlation between DM-related indices and gut microbes, in rats were investigated. Chebulic acid (0.368%), gallic acid (0.469%), andrographolide (1.304%), berberine (6.442%), and numerous polysaccharides were the most representative constituents in PHE. A more significant BW gain and a reduction in FBG level towards normal of PHE 600 mg/kg treated rats group were resulted at the end of 28th days of the study. Moreover, the composition of the gut microbiota corroborated the study's hypothesis, as evidenced by an increased ratio of Bacteroidetes to Firmicutes and some beneficial microbial species, including Prevotella copri and Lactobacillus hamster. The relative abundance of Bifidobacterium pseudolongum, Ruminococcus bromii, and Blautia producta was found to decline in PHE treatment groups as compared to diabetic group. The abundance of beneficial bacteria in PHE 600 mg/kg treatment group was concurrently associated with increased SCFAs concentrations of acetate and propionate (7.26 nmol/g and 4.13 nmol/g). The findings of this study suggest a promising approach to prevent DM by demonstrating that these naturally occurring compounds decreased FBG levels by increasing SCFAs content and SCFAs producing gut microbiota.

Mechanism of 2'-fucosyllactose degradation by human-associated Akkermansia

Among the first microorganisms to colonize the human gut of breastfed infants are bacteria capable of fermenting human milk oligosaccharides (HMOs). One of the most abundant HMOs, 2'-fucosyllactose (2'-FL), may specifically drive bacterial colonization of the intestine. Recently, differential growth has been observed across multiple species of Akkermansia on various HMOs including 2'-FL. In culture, we found growth of two species, A. muciniphila MucT and A. biwaensis CSUN-19,on HMOs corresponded to a decrease in the levels of 2'-FL and an increase in lactose, indicating that the first step in 2'-FL catabolism is the cleavage of fucose. Using phylogenetic analysis and transcriptional profiling, we found that the number and expression of fucosidase genes from two glycoside hydrolase (GH) families, GH29 and GH95, vary between these two species. During the mid-log phase of growth, the expression of several GH29 genes was increased by 2'-FL in both species, whereas the GH95 genes were induced only in A. muciniphila. We further show that one putative fucosidase and a β-galactosidase from A. biwaensis are involved in the breakdown of 2'-FL. Our findings indicate that the plasticity of GHs of human-associated Akkermansia sp. enables access to additional growth substrates present in HMOs, including 2'-FL. Our work highlights the potential for Akkermansia to influence the development of the gut microbiota early in life and expands the known metabolic capabilities of this important human symbiont.IMPORTANCEAkkermansia are mucin-degrading specialists widely distributed in the human population. Akkermansia biwaensis has recently been observed to have enhanced growth relative to other human-associated Akkermansia on multiple human milk oligosaccharides (HMOs). However, the mechanisms for enhanced growth are not understood. Here, we characterized the phylogenetic diversity and function of select genes involved in the growth of A. biwaensis on 2'-fucosyllactose (2'-FL), a dominant HMO. Specifically, we demonstrate that two genes in a genomic locus, a putative β-galactosidase and α-fucosidase, are likely responsible for the enhanced growth on 2'-FL. The functional characterization of A. biwaensis growth on 2'-FL delineates the significance of a single genomic locus that may facilitate enhanced colonization and functional activity of select Akkermansia early in life.

Effect of Trichinella spiralis-Derived Antigens on Nonalcoholic Fatty Liver Disease Induced by High-Fat Diet in Mice

Nonalcoholic fatty liver disease (NAFLD) is a liver disease characterized by hepatic steatosis, inflammation, and fibrosis, as well as gut dysbiosis. No approved effective therapeutic medicine is available to date for NAFLD. Helminth therapy is believed to be a novel direction and therapeutic strategy for NAFLD. Our previous study showed that Trichinella spiralis-derived antigens (TsAg) had the potential for partially alleviating obesity via regulating gut microbiota. However, the effect of TsAg on NAFLD remains unclear. In this study, high-fat diet (HFD)-induced model mice were treated with TsAg and microbiota transplantation experiments, and alterations in the pathogenesis of nonalcoholic liver disease were assessed. The results showed that TsAg markedly reduced hepatic steatosis, improved insulin resistance, and regulated the abnormal expression of hepatic lipid-related genes. Of note, TsAg ameliorated hepatic inflammation by decreasing pro-inflammatory TNF-α and IL-1β, suppressing hepatic macrophage infiltration, as well as promoting M2 macrophage polarization. Moreover, TsAg reversed gut dysbiosis, as especially indicated by an increase in beneficial bacteria (e.g., Akkermansiaceae and Rikenellaceae). Furthermore, our study found that TsAg reduced LPS hepatic translocation and hepatic TLR4/NF-κB signaling, which further contributed to inhibiting hepatic inflammation. In addition, TsAg inhibited hepatic oxidative stress involving Nrf2/NQO-1 signaling. Microbiota transplantation showed that TsAg-altered microbiota is sufficient to confer protection against NAFLD in HFD-induced mice. Overall, these findings suggest that TsAg involving gut-liver axis and Nrf2/NQO-1 signaling is a novel promising candidate for NAFLD treatment. TsAg restores intestinal microbiota and intestinal barrier to inhibit bacteria and LPS translocation into the liver, contributing to reduce inflammation, oxidative stress, and hepatic steatosis in the liver of NAFLD mice. The effects were attributed to, at least in part, the inactivation of NF-κB pathway and the activation of Nrf-2/NQO-1 pathway. This study provides new insights for understanding immune modulation by T. spiralis-derived products as well as the potential application of TsAg as a modality for NAFLD.

Divergent maturational patterns of the infant bacterial and fungal gut microbiome in the first year of life are associated with inter-kingdom community dynamics and infant nutrition

BACKGROUND

The gut microbiome undergoes primary ecological succession over the course of early life before achieving ecosystem stability around 3 years of age. These maturational patterns have been well-characterized for bacteria, but limited descriptions exist for other microbiota members, such as fungi. Further, our current understanding of the prevalence of different patterns of bacterial and fungal microbiome maturation and how inter-kingdom dynamics influence early-life microbiome establishment is limited.

RESULTS

We examined individual shifts in bacterial and fungal alpha diversity from 3 to 12 months of age in 100 infants from the CHILD Cohort Study. We identified divergent patterns of gut bacterial or fungal microbiome maturation in over 40% of infants, which were characterized by differences in community composition, inter-kingdom dynamics, and microbe-derived metabolites in urine, suggestive of alterations in the timing of ecosystem transitions. Known microbiome-modifying factors, such as formula feeding and delivery by C-section, were associated with atypical bacterial, but not fungal, microbiome maturation patterns. Instead, fungal microbiome maturation was influenced by prenatal exposure to artificially sweetened beverages and the bacterial microbiome, emphasizing the importance of inter-kingdom dynamics in early-life colonization patterns.

CONCLUSIONS

These findings highlight the ecological and environmental factors underlying atypical patterns of microbiome maturation in infants, and the need to incorporate multi-kingdom and individual-level perspectives in microbiome research to improve our understandings of gut microbiome maturation patterns in early life and how they relate to host health. Video Abstract.

Function and therapeutic prospects of next-generation probiotic Akkermansia muciniphila in infectious diseases

Akkermansia muciniphila is a gram-negative bacterium that colonizes the human gut, making up 3-5% of the human microbiome. A. muciniphila is a promising next-generation probiotic with clinical application prospects. Emerging studies have reported various beneficial effects of A. muciniphila including anti-cancer, delaying aging, reducing inflammation, improving immune function, regulating nervous system function, whereas knowledge on its roles and mechanism in infectious disease is currently unclear. In this review, we summarized the basic characteristics, genome and phenotype diversity, the influence of A. muciniphila and its derived components on infectious diseases, such as sepsis, virus infection, enteric infection, periodontitis and foodborne pathogen induced infections. We also provided updates on mechanisms how A. muciniphila protects intestinal barrier integrity and modulate host immune response. In summary, we believe that A. muciniphila is a promising therapeutic probiotic that may be applied for the treatment of a variety of infectious diseases.

Enhancing food waste reduction efficiency and high-value biomass production in Hermetia illucens rearing through bioaugmentation with gut bacterial agent

The black soldier fly (BSF) rearing technology has been a promising bioconversion method for food waste (FW) disposal. However, when used independently, it currently only achieves low efficiency and biomass transformation rates (BTR). This study screened and identified two strains of gut beneficial bacteria, Bacillus cereus and Bacterium YC-LK-LKJ45. The efficiency of a complex culture formulated by these strains was investigated, focusing on enhancing FW reduction and high-value biomass production during the rearing of BSF larvae. The coculture agent group (G1-10%, with two strains in 1:1 volume ratio at a 10 % dosage) exhibited higher larval yield (627.67 g·kg-1), BTR (47.90 %), FW reduction efficiency (80.67 %), and total protein and fat yield (261.99 g·kg-1and 46.24 g·kg-1) compared to the control and the monoculture agent group (which added a single gut beneficial bacteria agent, either Bacillus cereus or Bacterium YC-LK-LKJ45). The bacterial agent altered the richness and diversity of the gut microbial community of BSF, increasing the relative abundance of beneficial bacteria such as Bacillus, Oceano bacillus, and Akkermansia, while decreasing pathogenic bacteria, such as Acinetobacter and Escherichia-Shigella. Structural equation model quantification revealed that α-diversity (λ = 0.897, p < 0.001) and BTR (λ = 0.747, p < 0.001) are crucial drivers for enhancing high-value biomass during bioaugmentation rearing. This investigation provides a theoretical framework for the effective management of food waste using BSF, enhancing its decomposition and transformation into higher-value biomass.

Culturing the unculturables: strategies, challenges, and opportunities for gut microbiome study

Metagenome sequencing techniques revolutionized the field of gut microbiome study. However, it is equipped with experimental and computational biases, which affect the downstream analysis results. Also, live microbial strains are needed for a better understanding of host-microbial crosstalks and for designing next-generation treatment therapies based on probiotic strains and postbiotic molecules. Conventional culturing methodologies are insufficient to get the dark gut matter on the plate; therefore, there is an urgent need to propose novel culturing methods that can fill the limitations of metagenomics. The current work aims to provide a consolidated evaluation of the available methods for host-microbe interaction with an emphasis on in vitro culturing of gut microbes using organoids, gut on a chip, and gut bioreactor. Further, the knowledge of microbial crosstalk in the gut helps us to identify core microbiota, and key metabolites that will aid in designing culturing media and co-culturing systems for gut microbiome study. After the deeper mining of the current culturing methods, we recommend that 3D-printed intestinal cells in a multistage continuous flow reactor equipped with an extended organoid system might be a good practical choice for gut microbiota-based studies.

Probiotics, prebiotics, and postbiotics in health and disease

The gut microbiota and its homeostasis play a crucial role in human health. However, for some diseases related to the gut microbiota, current traditional medicines can only relieve symptoms, and it is difficult to solve the root causes or even cause side effects like disturbances in the gut microbiota. Increasing clinical studies and evidences have demonstrated that probiotics, prebiotics, and postbiotics can prevent and treat various diseases, but currently they can only be used as dietary supplements rather than medicines, which restricts the application of probiotics in the field of medicine. Here, this review analyzes the importance of gut microbiota in human health and the current problems of traditional medicines, and systematically summarizes the effectiveness and mechanisms of probiotics, prebiotics, and postbiotics in maintaining health and treating diseases based on animal models and clinical trials. And based on current research outcomes and development trends in this field, the challenges and prospects of their clinical application in maintaining health, alleviating and treating diseases are analyzed. It is hoped to promote the application of probiotics, prebiotics, and postbiotics in disease treatment and open up new frontiers in probiotic research.

Potential Effects of Akkermansia Muciniphila in Aging and Aging-Related Diseases: Current Evidence and Perspectives

Akkermansia muciniphila (A. muciniphila) is an anaerobic bacterium that widely colonizes the mucus layer of the human and animal gut. The role of this symbiotic bacterium in host metabolism, inflammation, and cancer immunotherapy has been extensively investigated over the past 20 years. Recently, a growing number of studies have revealed a link between A. muciniphila, and aging and aging-related diseases (ARDs). Research in this area is gradually shifting from correlation analysis to exploration of causal relationships. Here, we systematically reviewed the association of A. muciniphila with aging and ARDs (including vascular degeneration, neurodegenerative diseases, osteoporosis, chronic kidney disease, and type 2 diabetes). Furthermore, we summarize the potential mechanisms of action of A. muciniphila and offer perspectives for future studies.

Structure, Health Benefits, Mechanisms, and Gut Microbiota of Dendrobium officinale Polysaccharides: A Review

Dendrobium officinale polysaccharides (DOPs) are important active polysaccharides found in Dendrobium officinale, which is commonly used as a conventional food or herbal medicine and is well known in China. DOPs can influence the composition of the gut microbiota and the degradation capacity of these symbiotic bacteria, which in turn may determine the efficacy of dietary interventions. However, the necessary analysis of the relationship between DOPs and the gut microbiota is lacking. In this review, we summarize the extraction, structure, health benefits, and related mechanisms of DOPs, construct the DOPs-host axis, and propose that DOPs are potential prebiotics, mainly composed of 1,4-β-D-mannose, 1,4-β-D-glucose, and O-acetate groups, which induce an increase in the abundance of gut microbiota such as Lactobacillus, Bifidobacterium, Akkermansia, Bacteroides, and Prevotella. In addition, we found that when exposed to DOPs with different structural properties, the gut microbiota may exhibit different diversity and composition and provide health benefits, such as metabolism regulations, inflammation modulation, immunity moderation, and cancer intervention. This may contribute to facilitating the development of functional foods and health products to improve human health.

Machine learning: a powerful tool for identifying key microbial agents associated with specific cancer types

Machine learning (ML) includes a broad class of computer programs that improve with experience and shows unique strengths in performing tasks such as clustering, classification and regression. Over the past decade, microbial communities have been implicated in influencing the onset, progression, metastasis, and therapeutic response of multiple cancers. Host-microbe interaction may be a physiological pathway contributing to cancer development. With the accumulation of a large number of high-throughput data, ML has been successfully applied to the study of human cancer microbiomics in an attempt to reveal the complex mechanism behind cancer. In this review, we begin with a brief overview of the data sources included in cancer microbiomics studies. Then, the characteristics of the ML algorithm are briefly introduced. Secondly, the application progress of ML in cancer microbiomics is also reviewed. Finally, we highlight the challenges and future prospects facing ML in cancer microbiomics. On this basis, we conclude that the development of cancer microbiomics can not be achieved without ML, and that ML can be used to develop tumor-targeting microbial therapies, ultimately contributing to personalized and precision medicine.

Mechanism of 2'-Fucosyllactose degradation by Human-Associated Akkermansia

Among the first microorganisms to colonize the human gut of breastfed infants are bacteria capable of fermenting human milk oligosaccharides (HMOs). One of the most abundant HMOs, 2'-fucosyllactose (2'-FL), may specifically drive bacterial colonization of the intestine. Recently, differential growth has been observed across multiple species of Akkermansia on various HMOs including 2'FL. In culture, we found growth of two species, A. muciniphila Muc T and A. biwaensis CSUN-19, in HMOS corresponded to a decrease in the levels of 2'-FL and an increase in lactose, indicating that the first step in 2'-FL catabolism is the cleavage of fucose. Using phylogenetic analysis and transcriptional profiling, we found that the number and expression of fucosidase genes from two glycoside hydrolase (GH) families, GH29 and GH95, varies between these two species. During mid-log phase growth, the expression of several GH29 genes was increased by 2'-FL in both species, whereas the GH95 genes were induced only in A. muciniphila . We further show that one putative fucosidase and a β-galactosidase from A. biwaensis are involved in the breakdown of 2'-FL. Our findings indicate that that plasticity of GHs of human associated Akkermansia sp. enable access to additional growth substrates present in HMOs, including 2'-FL. Our work highlights the potential for Akkermansia to influence the development of the gut microbiota early in life and expands the known metabolic capabilities of this important human symbiont.

IMPORTANCE

Akkermansia are mucin degrading specialists widely distributed in the human population. Akkermansia biwaensis has recently been observed to have enhanced growth relative to other human associated Akkermansia on multiple human milk oligosaccharides (HMOs). However, the mechanisms for enhanced growth are not understood. Here, we characterized the phylogenetic diversity and function of select genes involved in growth of A. biwaensis on 2'-fucosyllactose (2'-FL), a dominant HMO. Specifically, we demonstrate that two genes in a genomic locus, a putative β-galactosidase and α-fucosidase, are likely responsible for the enhanced growth on 2'-FL. The functional characterization of A. biwaensis growth on 2'-FL delineates the significance of a single genomic locus that may facilitate enhanced colonization and functional activity of select Akkermansia early in life.

Insights into early evolutionary adaptations of the Akkermansia genus to the vertebrate gut

Akkermansia, a relevant mucin degrader from the vertebrate gut microbiota, is a member of the deeply branched Verrucomicrobiota, as well as the only known member of this phylum to be described as inhabitants of the gut. Only a few Akkermansia species have been officially described so far, although there is genomic evidence addressing the existence of more species-level variants for this genus. This niche specialization makes Akkermansia an interesting model for studying the evolution of microorganisms to their adaptation to the gastrointestinal tract environment, including which kind of functions were gained when the Akkermansia genus originated or how the evolutionary pressure functions over those genes. In order to gain more insight into Akkermansia adaptations to the gastrointestinal tract niche, we performed a phylogenomic analysis of 367 high-quality Akkermansia isolates and metagenome-assembled genomes, in addition to other members of Verrucomicrobiota. This work was focused on three aspects: the definition of Akkermansia genomic species clusters and the calculation and functional characterization of the pangenome for the most represented species; the evolutionary relationship between Akkermansia and their closest relatives from Verrucomicrobiota, defining the gene families which were gained or lost during the emergence of the last Akkermansia common ancestor (LAkkCA) and; the evaluation of the evolutionary pressure metrics for each relevant gene family of main Akkermansia species. This analysis found 25 Akkermansia genomic species clusters distributed in two main clades, divergent from their non-Akkermansia relatives. Pangenome analyses suggest that Akkermansia species have open pangenomes, and the gene gain/loss model indicates that genes associated with mucin degradation (both glycoside hydrolases and peptidases), (micro)aerobic metabolism, surface interaction, and adhesion were part of LAkkCA. Specifically, mucin degradation is a very ancestral innovation involved in the origin of Akkermansia. Horizontal gene transfer detection suggests that Akkermansia could receive genes mostly from unknown sources or from other Gram-negative gut bacteria. Evolutionary metrics suggest that Akkemansia species evolved differently, and even some conserved genes suffered different evolutionary pressures among clades. These results suggest a complex evolutionary landscape of the genus and indicate that mucin degradation could be an essential feature in Akkermansia evolution as a symbiotic species.

Protective Effect of Akkermansia muciniphila on the Preeclampsia-Like Mouse Model

Preeclampsia (PE) is known as a metabolism-related complication of pregnancy related to gut dysbiosis including the decreased abundance of Akkermansia muciniphila (A. muciniphila). However, the modulatory role of A. muciniphila as a supplement for PE remains ambiguous. This study investigated the effect of A. muciniphila administration on PE-like mice and its underlying mechanisms. A total of twenty-four C57BL/6 mice were randomly assigned into three groups. PE-like symptoms were induced by continuous injection of L-NAME intraperitoneally from gestational day (GD) 11 to GD18 combined with oral administration of pasteurized A. muciniphila during GD14-18 or not. Mice were sacrificed at GD19 to collect for further evaluation. Decreased A. muciniphila was observed in a successfully established PE-like model than normotensive pregnant control (NP), inversely correlated to increased systolic blood pressure blood and 24-h proteinuria. After supplementing with A. muciniphila, mice showed significantly minimized blood pressure and protein expression in urine, increased number of pups and weight of both embryos and placentas. In addition, colonies of bacteria, inflammatory cytokines (TNF-α and IL-6), and metabolic products of lipids including TC, FC, and TG were alleviated by A. muciniphila in the placentas. Among proteins linked with bowel barrier functions, diminished 2-AG and growing ZO-1 and occludin were attributable to A. muciniphila. Also, enhanced Treg/Th17 ratios were found in the intestines of mice treated with A. muciniphila. A. muciniphila facilitated alleviating PE-like symptoms and was beneficial as a novel probiotic therapeutic agent for PE.

A genetic system for Akkermansia muciniphila reveals a role for mucin foraging in gut colonization and host sterol biosynthesis gene expression

Akkermansia muciniphila, a mucophilic member of the gut microbiota, protects its host against metabolic disorders. Because it is genetically intractable, the mechanisms underlying mucin metabolism, gut colonization and its impact on host physiology are not well understood. Here we developed and applied transposon mutagenesis to identify genes important for intestinal colonization and for the use of mucin. An analysis of transposon mutants indicated that de novo biosynthesis of amino acids was required for A. muciniphila growth on mucin medium and that many glycoside hydrolases are redundant. We observed that mucin degradation products accumulate in internal compartments within bacteria in a process that requires genes encoding pili and a periplasmic protein complex, which we term mucin utilization locus (MUL) genes. We determined that MUL genes were required for intestinal colonization in mice but only when competing with other microbes. In germ-free mice, MUL genes were required for A. muciniphila to repress genes important for cholesterol biosynthesis in the colon. Our genetic system for A. muciniphila provides an important tool with which to uncover molecular links between the metabolism of mucins, regulation of lipid homeostasis and potential probiotic activities.

Akkermansia muciniphila in neuropsychiatric disorders: friend or foe?

An accumulating body of evidence suggests that the bacterium Akkermansia muciniphila exhibits positive systemic effects on host health, mainly by improving immunological and metabolic functions, and it is therefore regarded as a promising potential probiotic. Recent clinical and preclinical studies have shown that A. muciniphila plays a vital role in a variety of neuropsychiatric disorders by influencing the host brain through the microbiota-gut-brain axis (MGBA). Numerous studies observed that A. muciniphila and its metabolic substances can effectively improve the symptoms of neuropsychiatric disorders by restoring the gut microbiota, reestablishing the integrity of the gut mucosal barrier, regulating host immunity, and modulating gut and neuroinflammation. However, A. muciniphila was also reported to participate in the development of neuropsychiatric disorders by aggravating inflammation and influencing mucus production. Therefore, the exact mechanism of action of A. muciniphila remains much controversial. This review summarizes the proposed roles and mechanisms of A. muciniphila in various neurological and psychiatric disorders such as depression, anxiety, Parkinson's disease, Alzheimer's disease, multiple sclerosis, strokes, and autism spectrum disorders, and provides insights into the potential therapeutic application of A. muciniphila for the treatment of these conditions.

Effects of Lactiplantibacillus plantarum and Lacticaseibacillus paracasei supplementation on the faecal metabolome in children with coeliac disease autoimmunity: a randomised, double-blinded placebo-controlled clinical trial

Introduction

Coeliac disease is a lifelong immune-mediated enteropathy manifested as gluten intolerance in individuals carrying specific human leukocyte antigen (HLA) molecules. Other factors than genetics and gluten intake, however, may play a role in triggering the disease. The gut internal environment is thought to be one of these potential contributing factors, and it can be influenced throughout life.

Methods

We examine the impact of Lactiplantibacillus plantarum HEAL9 and Lacticaseibacillus paracasei 8700:2 supplementation on the faecal metabolome in genetically predisposed children having tissue transglutaminase autoantibodies, i.e., coeliac disease autoimmunity. Probiotic strains were selected based on their beneficial properties, including mucosal permeability and immune modulation effects. The intervention group (n = 40) and control group (n = 38) took the probiotics or placebo daily for 6 months in a double-blinded randomised trial. Faecal samples were collected at baseline and after 3 and 6 months and analysed using the 1H NMR for metabolome. The incorporation of 16S rRNA sequencing as a supportive dataset complemented the analysis of the metabolome data.

Results

During the 6 months of intervention, the stool concentrations of 4-hydroxyphenylacetate increased in the intervention group as compared to controls, whereas concentrations of threonine, valine, leucine, isoleucine, methionine, phenylalanine, aspartate, and fumarate decreased. Additionally, a noteworthy effect on the glycine, serine, and threonine metabolic pathway has been observed.

Conclusion

The findings suggest a modest yet significant impact of the probiotics on the faecal metabolome, primarily influencing proteolytic processes in the gut.

Clinical trial registration

ClinicalTrials.gov, NCT03176095.

Analysis of the fecal metagenome in long-term survivors of pancreas cancer

BACKGROUND

The 5-year overall survival of pancreas adenocarcinoma (PCa) remains less than 10%. Clinical and tumor genomic characteristics have not differentiated PCa long-term survivors (LTSs) from unselected patients. Preclinical studies using fecal transplant experiments from LTSs of PCa have revealed delayed tumor growth through unknown mechanisms involving the fecal microbiota. However, features of the fecal microbiome in patients with long-term survival are not well described.

METHODS

In this cross-sectional study, comprehensive shotgun metagenomics was performed on stool from PCa patients with long-term survival (n = 16). LTS was defined as >4 years from pancreatectomy and all therapy without recurrence. LTSs were compared to control patients with PCa who completed pancreatectomy and chemotherapy (n = 8). Stool was sequenced using an Illumina NextSeq500. Statistical analyses were performed in R with MicrobiomeSeq and Phyloseq for comparison of LTSs and controls.

RESULTS

All patients underwent pancreatectomy and chemotherapy before sample donation. The median time from pancreatectomy of 6 years (4-14 years) for LTSs without evidence of disease compared to a median disease-free survival of 1.8 years from pancreatectomy in the control group. No differences were observed in overall microbial diversity for LTSs and controls using Shannon/Simpson indexes. Significant enrichment of species relative abundance was observed in LTSs for the Ruminococacceae family specifically Faecalibacterium prausnitzii species as well as Akkermansia muciniphila species.

CONCLUSIONS

Stool from patients cured from PCa has more relative abundance of Faecalibacterium prausnitzii and Akkermansia muciniphila. Additional studies are needed to explore potential mechanisms by which the fecal microbiota may influence survival in PCa.

PLAIN LANGUAGE SUMMARY

Although pancreatic cancer treatments have improved, the number of long-term survivors has remained stagnant with a 5-year overall survival estimate of 9%. Emerging evidence suggests that microbes within the gastrointestinal tract can influence cancer response through activation of the immune system. In this study, we profiled the stool microbiome in long-term survivors of pancreas cancer and controls. Several enriched species previously associated with enhanced tumor immune response were observed including Faecalibacterium prausnitzii and Akkermansia muciniphila. These findings warrant additional study assessing mechanisms by which the fecal microbiota may enhance pancreatic cancer immune response.

Potential of Akkermansia muciniphila and its outer membrane proteins as therapeutic targets for neuropsychological diseases

The gut microbiota varies dramatically among individuals, and changes over time within the same individual, due to diversities in genetic backgrounds, diet, nutrient supplementations and use of antibiotics. Up until now, studies on dysbiosis of microbiota have expanded to a wider range of diseases, with Akkermansia muciniphila at the cross spot of many of these diseases. A. muciniphila is a Gram-negative bacterium that produces short-chain fatty acids (SCFAs), and Amuc_1100 is one of its most highly expressed outer membrane proteins. This review aims to summarize current knowledge on correlations between A. muciniphila and involved neuropsychological diseases published in the last decade, with a focus on the potential of this bacterium and its outer membrane proteins as therapeutic targets for these diseases, on the basis of evidence accumulated from animal and clinical studies, as well as mechanisms of action from peripheral to central nervous system (CNS).

Function of Akkermansia muciniphila in type 2 diabetes and related diseases

The prevalence of type 2 diabetes (T2D) is increasing worldwide, with many patients developing long-term complications that affect their cardiovascular, urinary, alimentary, and other systems. A growing body of literature has reported the crucial role of gut microbiota in metabolic diseases, one of which, Akkermansia muciniphila, is considered the "next-generation probiotic" for alleviating metabolic disorders and the inflammatory response. Although extensive research has been conducted on A. muciniphila, none has summarized its regulation in T2D. Hence, this review provides an overview of the effects and multifaceted mechanisms of A. muciniphila on T2D and related diseases, including improving metabolism, alleviating inflammation, enhancing intestinal barrier function, and maintaining microbiota homeostasis. Furthermore, this review summarizes dietary strategies for increasing intestinal A. muciniphila abundance and effective gastrointestinal delivery.

Gut-Associated Lymphatic Tissue in Food-Restricted Rats: Influence of Refeeding and Probiotic Supplementation

Anorexia nervosa (AN) is a severe and often chronic eating disorder that leads to alterations in the gut microbiome, which is known to influence several processes, such as appetite and body weight regulation, metabolism, gut permeability, inflammation, and gut-brain interactions. Using a translational activity-based anorexia (ABA) rat model, this study examined the effect of chronic food starvation, as well as multistrain probiotic supplementation and refeeding, on the structure of the gut and gut-associated lymphatic tissue (GALT). Our results indicated that ABA had an atrophic influence on intestinal morphology and increased the formation of GALT in the small bowel and colon. Higher formation of GALT in ABA rats appeared to be reversible upon application of a multistrain probiotic mixture and refeeding of the starved animals. This is the first time that increased GALT was found following starvation in the ABA model. Our results underscore a potential role of gut inflammatory alterations in the underlying pathophysiology of AN. Increased GALT could be linked to the gut microbiome, as probiotics were able to reverse this finding. These results emphasize the role of the microbiome-gut-brain axis in the pathomechanisms of AN and point to probiotics as potentially beneficial addendum in the treatment of AN.

Microbiota-sensitive drug delivery systems based on natural polysaccharides for colon targeting

Colon targeting is an ongoing challenge, particularly for the oral administration of biological drugs or local treatment of inflammatory bowel disease (IBD). In both cases, drugs are known to be sensitive to the harsh conditions of the upper gastrointestinal tract (GIT) and, thus, must be protected. Here, we provide an overview of recently developed colonic site-specific drug delivery systems based on microbiota sensitivity of natural polysaccharides. Polysaccharides act as a substrate for enzymes secreted by the microbiota located in the distal part of GIT. The dosage form is adapted to the pathophysiology of the patient and, thus, a combination of bacteria-sensitive and time-controlled release or pH-dependent systems can be used for delivery.

Microbiome Composition in Microscopic Colitis: A Systematic Review

Believed to be a rare cause of chronic diarrhoea, microscopic colitis (MC) is a condition with rising incidence. Many prevalent risk factors and the unknown pathogenesis of MC rationalise the need for studies on microbiota composition. PubMed, Scopus, Web of Science and Embase were searched. Eight case-control studies were included. The risk of bias was assessed with the Newcastle-Ottawa Scale. Clinical details on the study population and MC were poor. The most consistent result among the studies was a decreased Akkermansia genus in faecal samples. Other results were inconsistent due to the different taxonomic levels of the outcomes. Possible changes in different taxa were observed in patients who suffered from MC compared to healthy controls. The alpha diversity compared between MC and the diarrhoea control may suggest potential similarities. The beta diversity in MC compared to healthy and diarrhoeal populations showed no significant outcomes. The microbiome composition in MC possibly differed from the healthy control, but no agreement regarding taxa was made. It might be relevant to focus on possible factors influencing the microbiome composition and its relationship with other diarrhoeal diseases.

Role of Akkermansia in Human Diseases: From Causation to Therapeutic Properties

The gut microbiota plays a critical role in the modulation of host metabolism and immune response, and its impairment has been implicated in many gastrointestinal and extraintestinal diseases. Current evidence shows the well-documented role of A. muciniphila in maintaining the integrity of the intestinal barrier, modulating the host immune response, and improving several metabolic pathways, making it a key element in the pathogenesis of several human diseases. In this scenario, A. muciniphila is the most promising next-generation probiotic and one of the first microbial species suitable for specific clinical use when compared with traditional probiotics. Further studies are needed to provide more accurate insight into its mechanisms of action and to better elucidate its properties in several major areas, paving the way for a more integrated and personalized therapeutic approach that finally makes the most of our knowledge of the gut microbiota.

Akkermansia muciniphila Cell-Free Supernatant Improves Glucose and Lipid Metabolisms in Caenorhabditis elegans

To explore the mechanism by which Akkermansia muciniphila cell-free supernatant improves glucose and lipid metabolisms in Caenorhabditis elegans, the present study used different dilution concentrations of Akkermansia muciniphila cell-free supernatant as an intervention for with Caenorhabditis elegans under a high-glucose diet. The changes in lifespan, exercise ability, level of free radicals, and characteristic indexes of glucose and lipid metabolisms were studied. Furthermore, the expression of key genes of glucose and lipid metabolisms was detected by qRT-PCR. The results showed that A. muciniphila cell-free supernatant significantly improved the movement ability, prolonged the lifespan, reduced the level of ROS, and alleviated oxidative damage in Caenorhabditis elegans. A. muciniphila cell-free supernatant supported resistance to increases in glucose and triglyceride induced by a high-glucose diet and downregulated the expression of key genes of glucose metabolism, such as gsy-1, pygl-1, pfk-1.1, and pyk-1, while upregulating the expression of key genes of lipid metabolism, such as acs-2, cpt-4, sbp-1, and tph-1, as well as down-regulating the expression of the fat-7 gene to inhibit fatty acid biosynthesis. These findings indicated that A. muciniphila cell-free supernatant, as a postbiotic, has the potential to prevent obesity and improve glucose metabolism disorders and other diseases.

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

Akkermansia muciniphila is a promising next-generation beneficial microbe due to its natural presence in the mucus layer of the gut, its symbiotic ability to degrade mucus, and its capacity to improve the intestinal barrier function. A. muciniphila is able to counteract weight gain and immuno-metabolic disturbances in several animal models. Many of these disorders, including obesity and auto-immune diseases, have been associated with decreased gut barrier function and consequent increased inflammation. Since A. muciniphila was found to normalize these changes and strengthen the gut barrier function, it is hypothesized that other beneficial effects of A. muciniphila might be caused by this restoration. In search for A. muciniphila's mode of action in enhancing the gut barrier function and promoting health, we reasoned that secreted components or cell envelope components of A. muciniphila are interesting candidates as they can potentially reach and interact with the epithelial barrier. In this review, we focus on the potential mechanisms through which A. muciniphila can exert its beneficial effects on the host by the production of extracellular and secreted proteins, metabolites and cell envelope components. These products have been studied in isolation for their structure, signaling capacity, and in some cases, also for their effects in preclinical models. This includes the protein known as Amuc_1100, which we here rename as pilus-associated signaling (PAS) protein , the P9 protein encoded by Amuc_1631, the short-chain fatty acids acetate and propionate, and cell envelope components, such as phosphatidylethanolamine and peptidoglycan.

Akkermansia muciniphila as a Next-Generation Probiotic in Modulating Human Metabolic Homeostasis and Disease Progression: A Role Mediated by Gut-Liver-Brain Axes?

Appreciation of the importance of Akkermansia muciniphila is growing, and it is becoming increasingly relevant to identify preventive and/or therapeutic solutions targeting gut-liver-brain axes for multiple diseases via Akkermansia muciniphila. In recent years, Akkermansia muciniphila and its components such as outer membrane proteins and extracellular vesicles have been known to ameliorate host metabolic health and intestinal homeostasis. However, the impacts of Akkermansia muciniphila on host health and disease are complex, as both potentially beneficial and adverse effects are mediated by Akkermansia muciniphila and its derivatives, and in some cases, these effects are dependent upon the host physiology microenvironment and the forms, genotypes, and strain sources of Akkermansia muciniphila. Therefore, this review aims to summarize the current knowledge of how Akkermansia muciniphila interacts with the host and influences host metabolic homeostasis and disease progression. Details of Akkermansia muciniphila will be discussed including its biological and genetic characteristics; biological functions including anti-obesity, anti-diabetes, anti-metabolic-syndrome, anti-inflammation, anti-aging, anti-neurodegenerative disease, and anti-cancer therapy functions; and strategies to elevate its abundance. Key events will be referred to in some specific disease states, and this knowledge should facilitate the identification of Akkermansia muciniphila-based probiotic therapy targeting multiple diseases via gut-liver-brain axes.

Akkermansia muciniphila plays critical roles in host health

Akkermansia muciniphila, an intestinal microorganism, belongs to Verrucomicrobia, one of the most abundant microorganisms in the mammalian gut. It is a mucin-degrading bacterium that can colonise intestines of mammals such as humans and mice by utilising mucin as the only nitrogen and carbon source. When A. muciniphila colonises the intestine, its metabolites interact with the intestinal barrier, affecting host health by consolidating the intestinal barrier, regulating metabolic functions of the intestinal and circulatory systems, and regulating immune functions. This review summarised the mechanisms of A. muciniphila-host interactions that are relevant to host health. We focussed on characteristics of A. muciniphila in relation to its metabolites to provide a comprehensive understanding of A. muciniphila and its effects on host health and disease processes.

Gut microbiota and bile acids partially mediate the improvement of fibroblast growth factor 21 on methionine-choline-deficient diet-induced non-alcoholic fatty liver disease mice

Non-alcoholic fatty liver disease (NAFLD) is characterized by hepatic steatosis, inflammation, and fibrosis, as well as gut dysbiosis. Fibroblast growth factor 21 (FGF21), which regulates glucose and lipid metabolism, has been proven to have a good effect on NAFLD. However, the modulating process between FGF21 and gut microbiota remains unclear in treating NAFLD. Here, the fecal microbiota composition of 30 patients with NAFLD who had undergone liver biopsy and 29 matched healthy participants were studied, together with the fecal bile acid (BA) profile. Treatment with FGF21 was given in methionine-choline-deficient (MCD) diet-induced NAFLD model C57BL/6 mice. An antibiotic cocktail and fecal microbiota transplantation were used to further confirm the benefits of FGF21 that were partially attributable to the change in gut microbiota. Patients with NAFLD had higher serum FGF21 levels and dysregulated fecal microbiota compositions and fecal BA profiles. In NAFLD mice, FGF21 significantly reduced steatohepatitis and collagen deposition in vivo and restored intestinal structure. FGF21 treatment also changed gut microbiota composition and regulated dysbiosis in BA metabolism. After treatment with an antibiotic cocktail, FGF21 partially alleviated hepatic and intestinal damage in NAFLD mice. Furthermore, fecal microbiota transplantation from FGF21-treated mice showed benefits similar to FGF21 therapy. The improvement using FGF21 in MCD diet-induced NAFLD mice is partially mediated via gut microbiota and BA. Gut microbiota-regulated BA metabolism may be a potential target of FGF21 in improving NAFLD.

Microbiota Composition in Diverticular Disease: Implications for Therapy

Gut microbiota (GM) composition and its imbalance are crucial in the pathogenesis of several diseases, mainly those affecting the gastrointestinal tract. Colon diverticulosis and its clinical manifestations (diverticular disease, DD) are among the most common digestive disorders in developed countries. In recent literature, the role of GM imbalance in the onset of the different manifestations within the clinical spectrum of DD has been highlighted. This narrative review aims to summarize and critically analyze the current knowledge on GM dysbiosis in diverticulosis and DD by comparing the available data with those found in inflammatory bowel disease (IBD). The rationale for using probiotics to rebalance dysbiosis in DD is also discussed.

The Role of the Gallbladder, the Intestinal Barrier and the Gut Microbiota in the Development of Food Allergies and Other Disorders

The microbiota present in the gastrointestinal tract is involved in the development or prevention of food allergies and autoimmune disorders; these bacteria can enter the gallbladder and, depending on the species involved, can either be benign or cause significant diseases. Occlusion of the gallbladder, usually due to the presence of calculi blocking the bile duct, facilitates microbial infection and inflammation, which can be serious enough to require life-saving surgery. In addition, the biliary salts are secreted into the intestine and can affect the gut microbiota. The interaction between the gut microbiota, pathogenic organisms, and the human immune system can create intestinal dysbiosis, generating a variety of syndromes including the development of food allergies and autoimmune disorders. The intestinal microbiota can aggravate certain food allergies, which become severe when the integrity of the intestinal barrier is affected, allowing bacteria, or their metabolites, to cross the intestinal barrier and invade the bloodstream, affecting distal body organs. This article deals with health conditions and severe diseases that are either influenced by the gut flora or caused by gallbladder obstruction and inflammation, as well as putative treatments for those illnesses.

Characterization of antibiotic-resistance traits in Akkermansia muciniphila strains of human origin

Akkermansia muciniphila, a commensal bacterium commonly found in healthy gut microbiota, is widely considered a next-generation beneficial bacterium candidate to improve metabolic and inflammatory disorders. Recently the EFSA's Panel on Nutrition, Novel food, and Food Allergens has declared that pasteurized A. muciniphila DSM 22959^T (also Muc^T, ATCC BAA-835) can be considered safe as a novel food, opening the door to its commercialization as a food supplement. Despite its recognized health benefits, there is still little information regarding the antimicrobial susceptibility of this species and reference cut-off values to distinguish strains with intrinsic or acquired resistance from susceptible strains. In this study, we combined a genomic approach with the evaluation of the antibiotic susceptibility in five human A. muciniphila isolates. Genomic mining for antimicrobial resistance genes and MICs determinations revealed that only one strain harboring tetW gene showed resistance to tetracycline, whereas all A. muciniphila strains showed low sensitivity to ciprofloxacin and aminoglycosides with no genotypic correlation. Although all strains harbor the gene adeF, encoding for a subunit of the resistance-nodulation-cell division efflux pump system, potentially involved in ciprofloxacin resistance, the susceptibility towards ciprofloxacin determined in presence of efflux pump inhibitors was not affected. Overall, our outcomes revealed the importance to extend the antibiotic susceptibility test to a larger number of new isolates of A. muciniphila to better assess the safety aspects of this species.

Sialidase Inhibitors with Different Mechanisms

Sialidases, or neuraminidases, are enzymes that catalyze the hydrolysis of sialic acid (Sia)-containing molecules, mostly removal of the terminal Sia (desialylation). By desialylation, sialidase can modulate the functionality of the target compound and is thus often involved in biological pathways. Inhibition of sialidases with inhibitors is an important approach for understanding sialidase function and the underlying mechanisms and could serve as a therapeutic approach as well. Transition-state analogues, such as anti-influenza drugs oseltamivir and zanamivir, are major sialidase inhibitors. In addition, difluoro-sialic acids were developed as mechanism-based sialidase inhibitors. Further, fluorinated quinone methide-based suicide substrates were reported. Sialidase product analogue inhibitors were also explored. Finally, natural products have shown competitive inhibiton against viral, bacterial, and human sialidases. This Perspective describes sialidase inhibitors with different mechanisms and their activities and future potential, which include transition-state analogue inhibitors, mechanism-based inhibitors, suicide substrate inhibitors, product analogue inhibitors, and natural product inhibitors.

Rational consideration of Akkermansia muciniphila targeting intestinal health: advantages and challenges

As one of the promising next-generation probiotics (NGPs), Akkermansia muciniphila, a well-known mucin-degrading bacterium, has been proven to be closely related to the metabolic diseases of its human host. However, the role of A. muciniphila in the host’s intestinal health remains ambiguous. Here, we comprehensively summarize and discuss the characteristics, the distribution, and the colonization of A. muciniphila in the human gastrointestinal tract (GIT). We propose that the application of A. muciniphila as a biomarker for longevity, for diagnostics and prognostics of intestinal diseases, or for intestinal health should be cautiously considered. Precise dietary regulation can mediate the treatment of intestinal diseases by altering the abundance of A. muciniphila. Although the beneficial role of A. muciniphila and its component in intestinal inflammation has been discovered, in gnotobiotic mice with specific gut microbiota, certain genotype, and colorectal cancer, or in animal models infected with a specific pathogen, A. muciniphila may be related to the occurrence and development of intestinal diseases. Genomic analysis, emphasizing the strain-level phylogenetic differences of A. muciniphila, indicates that a clear description and discussion of each strain is critical before its practical application. Our review provides much needed insight for the precise application of A. muciniphila.

Akkermansia muciniphila: paradigm for next-generation beneficial microorganisms

Ever since Akkermansia muciniphila was discovered and characterized two decades ago, numerous studies have shown that the lack or decreased abundance of this commensal bacterium was linked with multiple diseases (such as obesity, diabetes, liver steatosis, inflammation and response to cancer immunotherapies). Although primarily based on simple associations, there are nowadays an increasing number of studies moving from correlations to causality. The causal evidence derived from a variety of animal models performed in different laboratories and recently was also recapitulated in a human proof-of-concept trial. In this Review, we cover the history of the discovery of A. muciniphila and summarize the numerous findings and main mechanisms of action by which this intestinal symbiont improves health. A comparison of this microorganism with other next-generation beneficial microorganisms that are being developed is also made.

Effect of a Proton Pump Inhibitor on the Duodenum Microbiome of Gastric Ulcer Patients

The gut microbiota are regarded as a functional organ that plays a substantial role in human health and disease. Proton pump inhibitors (PPIs) are widely used in medicine but can induce changes in the overall gut microbiome and cause disease-associated dysbiosis. The microbiome of the duodenum has not been sufficiently studied, and the effects of PPIs on the duodenal microbiome are poorly understood. In this study, we investigated the effect of PPI administration on duodenum microbiota in patients with a gastric ulcer. A total of 12 gastric ulcer patients were included, and PPI (Ilaprazole, Noltec^®, 10 mg) was prescribed in all patients for 4 weeks. A total of 17 samples from the second portion of the duodenum were analyzed. Microbiome compositions were assessed by sequencing the V3–V4 region of the 16s rRNA gene (Miseq). Changes in microbiota compositions after 4 weeks of PPI treatment were analyzed. a-Diversity was higher after PPI treatment (p = 0.02, at Chao1 index), and β-diversity was significantly different after treatment (p = 0.007). Welch’s t-test was used to investigate changes in phyla, genus, and species level, and the abundance of Akkermansia muciniphila, belonging to the phylum Verrucomicrobia, and Porphyromonas endodontalis, belonging to the phylum Bacteroidetes, was significantly increased after treatment (p = 0.044 and 0.05). PPI administration appears to induce duodenal microbiome dysbiosis while healing gastric ulcers. Further large-scale studies on the effects of PPIs on the duodenal microbiome are required.

Exploring Bacterial Attributes That Underpin Symbiont Life in the Monogastric Gut

The large bowel of monogastric animals, such as that of humans, is home to a microbial community (microbiota) composed of a diversity of mostly bacterial species. Interrelationships between the microbiota as an entity and the host are complex and lifelong and are characteristic of a symbiosis. The relationships may be disrupted in association with disease, resulting in dysbiosis. Modifications to the microbiota to correct dysbiosis require knowledge of the fundamental mechanisms by which symbionts inhabit the gut. This review aims to summarize aspects of niche fitness of bacterial species that inhabit the monogastric gut, especially of humans, and to indicate the research path by which progress can be made in exploring bacterial attributes that underpin symbiont life in the gut.