From the gut to the brain: the long journey of phenolic compounds with neurocognitive effects

The human gut microbiota is a complex community of micro-organisms that play a crucial role in maintaining overall health. Recent research has shown that gut microbes also have a profound impact on brain function and cognition, leading to the concept of the gut-brain axis. One way in which the gut microbiota can influence the brain is through the bioconversion of polyphenols to other bioactive molecules. Phenolic compounds are a group of natural plant metabolites widely available in the human diet, which have anti-inflammatory and other positive effects on health. Recent studies have also suggested that some gut microbiota-derived phenolic metabolites may have neurocognitive effects, such as improving memory and cognitive function. The specific mechanisms involved are still being studied, but it is believed that phenolic metabolites may modulate neurotransmitter signaling, reduce inflammation, and enhance neural plasticity. Therefore, to exert a protective effect on neurocognition, dietary polyphenols or their metabolites must reach the brain, or act indirectly by producing an increase in bioactive molecules such as neurotransmitters. Once ingested, phenolic compounds are subjected to various processes (eg, metabolization by gut microbiota, absorption, distribution) before they cross the blood-brain barrier, perhaps the most challenging stage of their trajectory. Understanding the role of phenolic compounds in the gut-brain axis has important implications for the development of new therapeutic strategies for neurological and psychiatric disorders. By targeting the gut microbiota and its production of phenolic metabolites, it may be possible to improve brain function and prevent cognitive decline. In this article, the current state of knowledge on the endogenous generation of phenolic metabolites by the gut microbiota and how these compounds can reach the brain and exert neurocognitive effects was reviewed.

The microbiota drives diurnal rhythms in tryptophan metabolism in the stressed gut

Chronic stress disrupts microbiota-gut-brain axis function and is associated with altered tryptophan metabolism, impaired gut barrier function, and disrupted diurnal rhythms. However, little is known about the effects of acute stress on the gut and how it is influenced by diurnal physiology. Here, we used germ-free and antibiotic-depleted mice to understand how microbiota-dependent oscillations in tryptophan metabolism would alter gut barrier function at baseline and in response to an acute stressor. Cecal metabolomics identified tryptophan metabolism as most responsive to a 15-min acute stressor, while shotgun metagenomics revealed that most bacterial species exhibiting rhythmicity metabolize tryptophan. Our findings highlight that the gastrointestinal response to acute stress is dependent on the time of day and the microbiome, with a signature of stress-induced functional alterations in the ileum and altered tryptophan metabolism in the colon.

Alterations in the gut microbiota and its metabolites contribute to metabolic maladaptation in dairy cows during the development of hyperketonemia

Metabolic maladaptation in dairy cows after calving can lead to long-term elevation of ketones, such as β-hydroxybutyrate (BHB), representing the condition known as hyperketonemia, which greatly influences the health and production performance of cows during the lactation period. Although the gut microbiota is known to alter in dairy cows with hyperketonemia, the association of microbial metabolites with development of hyperketonemia remains unknown. In this study, we performed a multi-omics analysis to investigate the associations between fecal microbial community, fecal/plasma metabolites, and serum markers in hyperketonemic dairy cows during the transition period. Dynamic changes in the abundance of the phyla Verrucomicrobiota and Proteobacteria were detected in the gut microbiota of dairy cows, representing an adaptation to enhanced lipolysis and abnormal glucose metabolism after calving. Random forest and univariate analyses indicated that Frisingicoccus is a key bacterial genus in the gut of cows during the development of hyperketonemia, and its abundance was positively correlated with circulating branched-chain amino acid levels and the ketogenesis pathway. Taurodeoxycholic acid, belonging to the microbial metabolite, was strongly correlated with an increase in blood BHB level, and the levels of other secondary bile acid in the feces and plasma were altered in dairy cows prior to the diagnosis of hyperketonemia, which link the gut microbiota and hyperketonemia. Our results suggest that alterations in the gut microbiota and its metabolites contribute to excessive lipolysis and insulin insensitivity during the development of hyperketonemia, providing fundamental knowledge about manipulation of gut microbiome to improve metabolic adaptability in transition dairy cows.IMPORTANCEAccumulating evidence is pointing to an important association between gut microbiota-derived metabolites and metabolic disorders in humans and animals; however, this association in dairy cows from late gestation to early lactation is poorly understood. To address this gap, we integrated longitudinal gut microbial (feces) and metabolic (feces and plasma) profiles to characterize the phenotypic differences between healthy and hyperketonemic dairy cows from late gestation to early lactation. Our results demonstrate that cows underwent excessive lipid mobilization and insulin insensitivity before hyperketonemia was evident. The bile acids are functional readouts that link gut microbiota and host phenotypes in the development of hyperketonemia. Thus, this work provides new insight into the mechanisms involved in metabolic adaptation during the transition period to adjust to the high energy and metabolic demands after calving and during lactation, which can offer new strategies for livestock management involving intervention of the gut microbiome to facilitate metabolic adaptation.

Conjugated Linoleic Acid Ameliorates High Fat-Induced Insulin Resistance via Regulating Gut Microbiota-Host Metabolic and Immunomodulatory Interactions

Interaction between gut microbiota, host immunity and metabolism has been suggested to crucially affect the development of insulin resistance (IR). This study aims to investigate how gut microbiota, inflammatory responses and metabolism in individuals with IR are affected by the supplementation of conjugated linoleic acid (CLA) and how this subsequently affects the pathophysiology of IR by using a high-fat diet-induced IR mouse model. Serum biochemical indices showed that 400 mg/kg body weight of CLA effectively attenuated hyperglycemia, hyperlipidemia, glucose intolerance and IR, while also promoting antioxidant capacities. Histomorphology, gene and protein expression analysis revealed that CLA reduced fat deposition and inflammation, and enhanced fatty acid oxidation, insulin signaling and glucose transport in adipose tissue or liver. Hepatic transcriptome analysis confirmed that CLA inhibited inflammatory signaling pathways and promoted insulin, PI3K-Akt and AMPK signaling pathways, as well as linoleic acid, arachidonic acid, arginine and proline metabolism. Gut microbiome analysis further revealed that these effects were highly associated with the enriched bacteria that showed positive correlation with the production of short-chain fatty acids (SCFAs), as well as the improved SCFAs production simultaneously. This study highlights the therapeutic actions of CLA on ameliorating IR via regulating microbiota-host metabolic and immunomodulatory interactions, which have important implications for IR control.

Tapping the biosynthetic potential of marine Bacillus licheniformis LHG166, a prolific sulphated exopolysaccharide producer: structural insights, bio-prospecting its antioxidant, antifungal, antibacterial and anti-biofilm potency as a novel anti-infective lead

The escalating global threat of antimicrobial resistance necessitates prospecting uncharted microbial biodiversity for novel therapeutic leads. This study mines the promising chemical richness of Bacillus licheniformis LHG166, a prolific exopolysaccharide (EPSR2-7.22 g/L). It comprised 5 different monosaccharides with 48.11% uronic acid, 17.40% sulfate groups, and 6.09% N-acetyl glucosamine residues. EPSR2 displayed potent antioxidant activity in DPPH and ABTS+, TAC and FRAP assays. Of all the fungi tested, the yeast Candida albicans displayed the highest susceptibility and antibiofilm inhibition. The fungi Aspergillus niger and Penicillium glabrum showed moderate EPSR2 susceptibility. In contrast, the fungi Mucor circinelloides and Trichoderma harzianum were resistant. Among G+ve tested bacteria, Enterococcus faecalis was the most susceptible, while Salmonella typhi was the most sensitive to G-ve pathogens. Encouragingly, EPSR2 predominantly demonstrated bactericidal effects against both bacterial classes based on MBC/MIC of either 1 or 2 superior Gentamicin. At 75% of MBC, EPSR2 displayed the highest anti-biofilm activity of 88.30% against B. subtilis, while for G-ve antibiofilm inhibition, At 75% of MBC, EPSR2 displayed the highest anti-biofilm activity of 96.63% against Escherichia coli, Even at the lowest dose of 25% MBC, EPSR2 reduced biofilm formation by 84.13% in E. coli, 61.46% in B. subtilis. The microbial metabolite EPSR2 from Bacillus licheniformis LHG166 shows promise as an eco-friendly natural antibiotic alternative for treating infections and oxidative stress.

Our extended microbiome: The human-relevant metabolites and biology of fermented foods

One of the key modes of microbial metabolism occurring in the gut microbiome is fermentation. This energy-yielding process transforms common macromolecules like polysaccharides and amino acids into a wide variety of chemicals, many of which are relevant to microbe-microbe and microbe-host interactions. Analogous transformations occur during the production of fermented foods, resulting in an abundance of bioactive metabolites. In foods, the products of fermentation can influence food safety and preservation, nutrient availability, and palatability and, once consumed, may impact immune and metabolic status, disease expression, and severity. Human signaling pathways perceive and respond to many of the currently known fermented food metabolites, though expansive chemical novelty remains to be defined. Here we discuss several aspects of fermented food-associated microbes and metabolites, including a condensed history, current understanding of their interactions with hosts and host-resident microbes, connections with commercial probiotics, and opportunities for future research on human health and disease and food sustainability.

The microbiome: an integral player in immune homeostasis and inflammation in the respiratory tract

The last decade of microbiome research has highlighted its fundamental role in systemic immune and metabolic homeostasis. The microbiome plays a prominent role during gestation and into early life, when maternal lifestyle factors shape immune development of the newborn. Breast milk further shapes gut colonization, supporting the development of tolerance to commensal bacteria and harmless antigens while preventing outgrowth of pathogens. Environmental microbial and lifestyle factors that disrupt this process can dysregulate immune homeostasis, predisposing infants to atopic disease and childhood asthma. In health, the low-biomass lung microbiome, together with inhaled environmental microbial constituents, establishes the immunological set point that is necessary to maintain pulmonary immune defense. However, in disease perturbations to immunological and physiological processes allow the upper respiratory tract to act as a reservoir of pathogenic bacteria, which can colonize the diseased lung and cause severe inflammation. Studying these host-microbe interactions in respiratory diseases holds great promise to stratify patients for suitable treatment regimens and biomarker discovery to predict disease progression. Preclinical studies show that commensal gut microbes are in a constant flux of cell division and death, releasing microbial constituents, metabolic by-products, and vesicles that shape the immune system and can protect against respiratory diseases. The next major advances may come from testing and utilizing these microbial factors for clinical benefit and exploiting the predictive power of the microbiome by employing multiomics analysis approaches.

Protective effects of butyrate on cerebral ischaemic injury in animal models: a systematic review and meta-analysis

Introduction

Cerebral ischaemic stroke is a common disease that poses a serious threat to human health. Butyrate is an important metabolite of intestinal microorganisms. Recent studies have shown that butyrate has a significant protective effect in animal models of cerebral ischaemic injury.

Objective

The aim of this study was to evaluate the protective effect of butyrate on cerebral ischaemic stroke by meta-analysis, aiming to provide a scientific basis for the clinical application of butyrate in patients with cerebral ischaemia.

Materials and methods

A systematic search was conducted for all relevant studies published before 23 January 2024, in PubMed, Web of Science, Cochrane Library, and Embase. Methodological quality was assessed using Syrcle's risk of bias tool for animal studies. Data were analysed using Rev Man 5.3 software.

Results

A total of nine studies were included, and compared with controls, butyrate significantly increased BDNF levels in the brain (SMD = 2.33, 95%CI = [1.20, 3.47], p < 0.005) and P-Akt expression (SMD = 3.53, 95% CI = [0.97, 6.10], p < 0.05). Butyrate also decreased IL-β levels in the brain (SMD = -2.02, 95% CI = [-3.22, -0.81], p < 0.005), TNF-α levels (SMD = -0.86, 95% CI = [-1.60, -0.12], p < 0.05), and peripheral vascular IL-1β levels (SMD = -2.10, 95%CI = [-3.59, -0.61], p < 0.05). In addition, butyrate reduced cerebral infarct volume (MD = -11.29, 95%CI = [-17.03, -5.54], p < 0.05), mNSS score (MD = -2.86, 95%CI = [-4.12, -1.60], p < 0.005), foot fault score (MD = -7.59, 95%CI = [-9.83, -5, 35], p < 0.005), and Morris water maze time (SMD = -2.49, 95%CI = [-4.42, -0.55], p < 0.05).

Conclusion

The results of this study indicate that butyrate has a protective effect on cerebral ischaemic stroke in animal models, and the mechanism is related to reducing inflammation and inhibiting apoptosis. It provides an evidence-based basis for the future clinical development of butyrate in the treatment of ischaemic stroke.

Systematic Review Registration

https://www.crd.york.ac.uk/PROSPERO/, CRD42023482844.

Electroacupuncture at ST25 corrected gut microbial dysbiosis and SNpc lipid peroxidation in Parkinson's disease rats

Introduction

Parkinson's disease (PD) remains one kind of a complex, progressive neurodegenerative disease. Levodopa and dopamine agonists as widely utilized PD therapeutics have not shown significant positive long-term outcomes. Emerging evidences indicate that electroacupuncture (EA) have potential effects on the therapy of nervous system disorders, particularly PD, but its specific underlying mechanism(s) remains poorly understood, leading to the great challenge of clinical application and management. Previous study has shown that acupuncture ameliorates PD motor symptoms and dopaminergic neuron damage by modulating intestinal dysbiosis, but its intermediate pathway has not been sufficiently investigated.

Methods

A rat model of PD was induced using rotenone. The therapeutic effect of EA on PD was assessed using the pole and rotarod tests and immunohistostaining for tyrosine hydroxylase (TH) in the substantia nigra (SN) of brain. The role of gut microbiota was explored using 16S rRNA gene sequencing and metabonomic analysis. PICRUSt2 analysis, lipidomic analysis, LPS and inflammatory factor assays were used for subsequent exploration and validation. Correlation analysis was used to identify the key bacteria that EA regulates lipid metabolism to improve PD.

Results

The present study firstly reappeared the effects of EA on protecting motor function and dopaminergic neurons and modulation of gut microbial dysbiosis in rotenone-induced PD rat model. EA improved motor dysfunction (via the pole and rotarod tests) and protected TH+ neurons in PD rats. EA increased the abundance of beneficial bacteria such as Lactobacillus, Dubosiella and Bifidobacterium and decreased the abundance of Escherichia-Shigella and Morganella belonging to Pseudomonadota, suggesting that the modulation of gut microbiota by EA improving the symptoms of PD motility via alleviating LPS-induced inflammatory response and oxidative stress, which was also validated by various aspects such as microbial gene functional analysis, fecal metabolomics analysis, LPS and inflammatory factor assays and SNpc lipidomics analysis. Moreover, correlation analyses also verified strong correlations of Escherichia-Shigella and Morganella with motor symptoms and SNpc lipid peroxidation, explicating targets and intermediate pathways through which EA improve PD exercise symptom.

Conclusion

Our results indicate that the improvement of motor function in PD model by EA may be mediated in part by restoring the gut microbiota, which intermediate processes involve circulating endotoxins and inflammatory mediators, SNpc oxidative stress and lipid peroxidation. The gut-microbiome - brain axis may be a potential mechanism of EA treatment for the PD.

A cross talk between microbial metabolites and host immunity: Its relevance for allergic diseases

BACKGROUND

Allergic diseases, including respiratory and food allergies, as well as allergic skin conditions have surged in prevalence in recent decades. In allergic diseases, the gut microbiome is dysbiotic, with reduced diversity of beneficial bacteria and increased abundance of potential pathogens. Research findings suggest that the microbiome, which is highly influenced by environmental and dietary factors, plays a central role in the development, progression, and severity of allergic diseases. The microbiome generates metabolites, which can regulate many of the host's cellular metabolic processes and host immune responses.

AIMS AND METHODS

Our goal is to provide a narrative and comprehensive literature review of the mechanisms through which microbial metabolites regulate host immune function and immune metabolism both in homeostasis and in the context of allergic diseases.

RESULTS AND DISCUSSION

We describe key microbial metabolites such as short-chain fatty acids, amino acids, bile acids and polyamines, elucidating their mechanisms of action, cellular targets and their roles in regulating metabolism within innate and adaptive immune cells. Furthermore, we characterize the role of bacterial metabolites in the pathogenesis of allergic diseases including allergic asthma, atopic dermatitis and food allergy.

CONCLUSION

Future research efforts should focus on investigating the physiological functions of microbiota-derived metabolites to help develop new diagnostic and therapeutic interventions for allergic diseases.

Aromatic amino acid metabolites alter interferon signaling and influenza pathogenesis

The ability of gut microbial metabolites to influence the host is increasingly recognized. The microbiota extensively metabolizes the three aromatic amino acids, tryptophan, tyrosine, and phenylalanine. Previously we have found that a metabolite of tyrosine, 4-OH-phenylpropionic acid, can enhance type I interferon (IFN) signaling and protect from influenza pathogenesis in a murine model. Herein we screened 17 related aromatic amino acid metabolites for effects on IFN signaling in human lung epithelial cells and monocytes alone and in the presence of IFN-β, influenza, and LPS. While the tryptophan family metabolites reduced IFN signaling in both cell types, the tyrosine and phenylalanine metabolites had varied effects, which were cell-type dependent. Pooled treatment of all these metabolites reduced IFN signaling in both cell types and suggested a tryptophan metabolite effect dominance. Strikingly, when all the metabolites were pooled together, we found reduced influenza recovery in both cell types. RNA sequencing further validated reduced viral loads and decreased IFN signaling. Single gene silencing of significantly upregulated genes identified by RNA sequencing (EGR2, ATP6VD02, SPOCK1, and IL31RA) did not completely abrogate the metabolite induced decrease in IFN signaling. However, these upregulated targets suggested a mechanistic link to TGF-beta signaling. Treatment with a TGF-beta inhibitor and combined targeted gene silencing led to a significant reversal of metabolite induced IFN signaling suppression. Finally, we demonstrated that intranasal administration of these metabolites prior to influenza infection led to reduced animal morbidity, viral titers, and inflammation. Our work implies that microbial metabolites can alter IFN signaling mechanistically through TGF-beta and promote beneficial outcomes during influenza infection.

The contribution of age-related changes in the gut-brain axis to neurological disorders

Trillions of microbes live symbiotically in the host, specifically in mucosal tissues such as the gut. Recent advances in metagenomics and metabolomics have revealed that the gut microbiota plays a critical role in the regulation of host immunity and metabolism, communicating through bidirectional interactions in the microbiota-gut-brain axis (MGBA). The gut microbiota regulates both gut and systemic immunity and contributes to the neurodevelopment and behaviors of the host. With aging, the composition of the microbiota changes, and emerging studies have linked these shifts in microbial populations to age-related neurological diseases (NDs). Preclinical studies have demonstrated that gut microbiota-targeted therapies can improve behavioral outcomes in the host by modulating microbial, metabolomic, and immunological profiles. In this review, we discuss the pathways of brain-to-gut or gut-to-brain signaling and summarize the role of gut microbiota and microbial metabolites across the lifespan and in disease. We highlight recent studies investigating 1) microbial changes with aging; 2) how aging of the maternal microbiome can affect offspring health; and 3) the contribution of the microbiome to both chronic age-related diseases (e.g., Parkinson's disease, Alzheimer's disease and cerebral amyloidosis), and acute brain injury, including ischemic stroke and traumatic brain injury.

Microbial metabolites are involved in tumorigenesis and development by regulating immune responses

The human microbiota is symbiotic with the host and can create a variety of metabolites. Under normal conditions, microbial metabolites can regulate host immune function and eliminate abnormal cells in a timely manner. However, when metabolite production is abnormal, the host immune system might be unable to identify and get rid of tumor cells at the early stage of carcinogenesis, which results in tumor development. The mechanisms by which intestinal microbial metabolites, including short-chain fatty acids (SCFAs), microbial tryptophan catabolites (MTCs), polyamines (PAs), hydrogen sulfide, and secondary bile acids, are involved in tumorigenesis and development by regulating immune responses are summarized in this review. SCFAs and MTCs can prevent cancer by altering the expression of enzymes and epigenetic modifications in both immune cells and intestinal epithelial cells. MTCs can also stimulate immune cell receptors to inhibit the growth and metastasis of the host cancer. SCFAs, MTCs, bacterial hydrogen sulfide and secondary bile acids can control mucosal immunity to influence the occurrence and growth of tumors. Additionally, SCFAs, MTCs, PAs and bacterial hydrogen sulfide can also affect the anti-tumor immune response in tumor therapy by regulating the function of immune cells. Microbial metabolites have a good application prospect in the clinical diagnosis and treatment of tumors, and our review provides a good basis for related research.

Postbiotic production: harnessing the power of microbial metabolites for health applications

Postbiotics, which are bioactive substances derived from the metabolic processes of beneficial microbes, have received considerable attention in the field of microbiome science in recent years, presenting a promising path for exploration and innovation. This comprehensive analysis looks into the multidimensional terrain of postbiotic production, including an extensive examination of diverse postbiotic classes, revealing their sophisticated mechanisms of action and highlighting future applications that might significantly affect human health. The authors thoroughly investigate the various mechanisms that support postbiotic production, ranging from conventional fermentation procedures to cutting-edge enzyme conversion and synthetic biology approaches. The review, as an acknowledgment of the field's developing nature, not only highlights current achievements but also navigates through the problems inherent in postbiotic production. In order to successfully include postbiotics in therapeutic interventions and the production of functional food ingredients, emphasis is given to critical elements, including improving yields, bolstering stability, and assuring safety. The knowledge presented herein sheds light on the expanding field of postbiotics and their potential to revolutionize the development of novel therapeutics and functional food ingredients.

From gut to placenta: understanding how the maternal microbiome models life-long conditions

The microbiome -defined as the microbiota (bacteria, archaea, lower and higher eukaryotes), their genomes, and the surrounding environmental conditions- has a well-described range of physiological functions. Thus, an imbalance of the microbiota composition -dysbiosis- has been associated with pregnancy complications or adverse fetal outcomes. Although there is controversy about the existence or absence of a microbiome in the placenta and fetus during healthy pregnancy, it is known that gut microbiota can produce bioactive metabolites that can enter the maternal circulation and may be actively or passively transferred through the placenta. Furthermore, the evidence suggests that such metabolites have some effect on the fetus. Since the microbiome can influence the epigenome, and modifications of the epigenome could be responsible for fetal programming, it can be experimentally supported that the maternal microbiome and its metabolites could be involved in fetal programming. The developmental origin of health and disease (DOHaD) approach looks to understand how exposure to environmental factors during periods of high plasticity in the early stages of life (e.g., gestational period) influences the program for disease risk in the progeny. Therefore, according to the DOHaD approach, the influence of maternal microbiota in disease development must be explored. Here, we described some of the diseases of adulthood that could be related to alterations in the maternal microbiota. In summary, this review aims to highlight the influence of maternal microbiota on both fetal development and postnatal life, suggesting that dysbiosis on this microbiota could be related to adulthood morbidity.

Oregano essential oil modulates colonic homeostasis and intestinal barrier function in fattening bulls

Oregano essential oil (OEO) primarily contains phenolic compounds and can serve as a dietary supplement for fattening bulls. However, the precise molecular mechanism underlying this phenomenon remains largely elusive. Therefore, this study investigated the impact of adding OEO to diet on the integrity of the intestinal barrier, composition of the colonic microbiome, and production of microbial metabolites in fattening bulls. Our goal was to provide insights into the utilization of plant essential oil products in promoting gastrointestinal health and welfare in animals. We employed amplicon sequencing and metabolome sequencing techniques to investigate how dietary supplementation with OEO impacted the intestinal barrier function in bulls. The inclusion of OEO in the diet resulted in several notable effects on the colon of fattening bulls. These effects included an increase in the muscle thickness of the colon, goblet cell number, short-chain fatty acid concentrations, digestive enzyme activity, relative mRNA expression of intestinal barrier-related genes, and relative expression of the anti-inflammatory factor IL-10. Additionally, α-amylase activity and the relative mRNA expression of proinflammatory cytokines decreased. Moreover, dietary OEO supplementation increased the abundance of intestinal Bacteroides, Coprobacillus, Lachnospiraceae_UCG_001, and Faecalitalea. Metabolomic analysis indicated that OEO primarily increased the levels of 5-aminovaleric acid, 3-methoxysalicylic acid, and creatinine. In contrast, the levels of maltose, lactulose, lactose, and D-trehalose decreased. Correlation analysis showed that altered colonic microbes and metabolites affected intestinal barrier function. Taken together, these results demonstrate that OEO facilitates internal intestinal environmental homeostasis by promoting the growth of beneficial bacteria while inhibiting harmful ones.

Parity modulates impact of BMI and gestational weight gain on gut microbiota in human pregnancy

Dysregulation of maternal adaptations to pregnancy due to high pre-pregnancy BMI (pBMI) or excess gestational weight gain (GWG) is associated with worsened health outcomes for mothers and children. Whether the gut microbiome contributes to these adaptations is unclear. We longitudinally investigated the impact of pBMI and GWG on the pregnant gut microbiome. We show that the gut microbiota of participants with higher pBMI changed less over the course of pregnancy in primiparous but not multiparous participants. This suggests that previous pregnancies may have persistent impacts on maternal adaptations to pregnancy. This ecological memory appears to be passed on to the next generation, as parity modulated the impact of maternal GWG on the infant gut microbiome. This work supports a role of the gut microbiome in maternal adaptations to pregnancy and highlights the need for longitudinal sampling and accounting for parity as key considerations for studies of the microbiome in pregnancy and infants. Understanding how these factors contribute to and shape maternal health is essential for the development of interventions impacting the microbiome, including pre/probiotics.

The role of microbiota in tumorigenesis, progression and treatment of bladder cancer

For decades, the urinary system was regarded as a sterile environment due to the absence of any bacterial growth in clinical standard urine cultures from healthy individuals. However, a diverse array of microbes colonizes the urinary system in small quantities, exhibiting a variable compositional signature influenced by differences in sex, age, and pathological state. Increasing pieces of evidence suggest microbiota exists in tumor tissue and plays a crucial role in tumor microenvironment based on research in multiple cancer models. Current studies about microbiota and bladder cancer have preliminarily characterized the bladder cancer-related microbiota, but how the microbiota influences the biological behavior of bladder cancer remains unclarified. This review summarizes the characteristics of microbiota in bladder cancer, aims to propose possible mechanisms that microbiota acts in tumorigenesis and progression of bladder cancer based on advances in gut microbiota, and discusses the potential clinical application of microbiota in bladder cancer.

Buckwheat (Fagopyrum esculentum) Hulls Are a Rich Source of Fermentable Dietary Fibre and Bioactive Phytochemicals

Pseudo-cereals such as buckwheat (Fagopyrum esculentum) are valid candidates to promote diet biodiversity and nutrition security in an era of global climate change. Buckwheat hulls (BHs) are currently an unexplored source of dietary fibre and bioactive phytochemicals. This study assessed the effects of several bioprocessing treatments (using enzymes, yeast, and combinations of both) on BHs' nutrient and phytochemical content, their digestion and metabolism in vitro (using a gastrointestinal digestion model and mixed microbiota from human faeces). The metabolites were measured using targeted LC-MS/MS and GC analysis and 16S rRNA gene sequencing was used to detect the impact on microbiota composition. BHs are rich in insoluble fibre (31.09 ± 0.22% as non-starch polysaccharides), protocatechuic acid (390.71 ± 31.72 mg/kg), and syringaresinol (125.60 ± 6.76 mg/kg). The bioprocessing treatments significantly increased the extractability of gallic acid, vanillic acid, p-hydroxybenzoic acid, syringic acid, vanillin, syringaldehyde, p-coumaric acid, ferulic acid, caffeic acid, and syringaresinol in the alkaline-labile bound form, suggesting the bioaccessibility of these phytochemicals to the colon. Furthermore, one of the treatments, EC_2 treatment, increased significantly the in vitro upper gastrointestinal release of bioactive phytochemicals, especially for protocatechuic acid (p < 0.01). The BH fibre was fermentable, promoting the formation mainly of propionate and, to a lesser extent, butyrate formation. The EM_1 and EC_2 treatments effectively increased the content of insoluble fibre but had no effect on dietary fibre fermentation (p > 0.05). These findings promote the use of buckwheat hulls as a source of dietary fibre and phytochemicals to help meet dietary recommendations and needs.

Influence of Microbiota-Related Metabolites Associated with Inflammation and Sepsis on the Peroxidase Activity of Cyclooxygenase in Healthy Human Monocytes and Acute Monocytic Leukemia Cells

The human microbiota produces metabolites that can enter the bloodstream and exert systemic effects on various functions in both healthy and pathological states. We have studied the participation of microbiota-related metabolites in bacterial infection by examining their influence on the activity of cyclooxygenase (COX) as a key enzyme of inflammation. The influence of aromatic microbial metabolites, derivatives of phenylalanine (phenylpropionic acid, PPA), tyrosine (4-hydroxyphenyllactic acid, HPLA), and tryptophan (indolacetic acids, IAA), the concentrations of which in the blood change notably during sepsis, was evaluated. Also, the effect of itaconic acid (ITA) was studied, which is formed in macrophages under the action of bacterial lipopolysaccharides (LPS) and appears in the blood in the early stages of infection. Metabiotic acetyl phosphate (AcP) as a strong acetylating agent was also tested. The activity of COX was measured via the TMPD oxidation colorimetric assay using the commercial pure enzyme, cultured healthy monocytes, and the human acute monocytic leukemia cell line THP-1. All metabolites in the concentration range of 100-500 μM lowered the activity of COX. The most pronounced inhibition was observed on the commercial pure enzyme, reaching up to 40% in the presence of AcP and 20-30% in the presence of the other metabolites. On cell lysates, the effect of metabolites was preserved, although it significantly decreased, probably due to their interaction with other targets subject to redox-dependent and acetylation processes. The possible contribution of the redox-dependent action of microbial metabolites was confirmed by assessing the activity of the enzyme in the presence of thiol reagents and in model conditions, when the COX-formed peroxy intermediate was replaced with tert-butyl hydroperoxide (TBH). The data show the involvement of the microbial metabolites in the regulation of COX activity, probably due to their influence on the peroxidase activity of the enzyme.

Analysis of 4-Hydroxyphenyllactic Acid and Other Diagnostically Important Metabolites of α-Amino Acids in Human Blood Serum Using a Validated and Sensitive Ultra-High-Pressure Liquid Chromatography-Tandem Mass Spectrometry Method

The profile of and dynamic concentration changes in tyrosine, phenylalanine, and tryptophan metabolites in blood are of great interest since they could be considered potential biomarkers of different disorders. Some aromatic metabolites, such as 4-hydroxyphenyllactic, 4-hydroxyphenylacetic, phenyllactic, and 4-hydroxybenzoic acids have previously demonstrated their diagnostic significance in critically ill patients and patients with post-COVID-19 syndrome. In this study, a sensitive method, including serum protein precipitation with methanol and ultra-high-pressure liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) detection, was developed and validated for six phenyl- and five indole-containing acids in human serum. The liquid-liquid extraction was also examined, but it demonstrated unsatisfactory results based on analyte recoveries and the matrix effect. However, the recoveries for all analytes reached 100% and matrix effects were not observed using protein precipitation. This made it possible to use deionized water as a blank matrix. The lower limits of quantitation (LLOQs) were from 0.02 to 0.25 μmol/L. The validated method was used for the analysis of serum samples of healthy volunteers (n = 48) to reveal the reference values of the target analytes. The concentrations of the most clinically significant metabolite 4-hydroxyphenyllactic acid, which were revealed using UPLC-MS/MS and a previously developed gas chromatography-mass spectrometry method, were completely comparable. The proposed UPLC-MS/MS protocol can be used in the routine clinical practice of medical centers.

[Gut microbial dysbiosis under space environment: a review]

Unique factors in the space environment can cause dysbiosis of astronauts' gut microbiota and its metabolites, which may exert systematic physiological effects on human body. Recent progress regarding the effect of space flight/simulated space environment (SF/SPE) on the composition of gut microbiota and its metabolites was reviewed in this paper. SF/SPE may cause the increase of invasive pathogenic bacteria and the decrease of beneficial bacteria, aggravating intestinal inflammation and increasing intestinal permeability. SF/SPE may also cause the decrease of beneficial metabolites or the increase of harmful metabolites of gut microbiota, leading to metabolism disorder in vivo, or inducing damage of other systems, thus not beneficial to the health and working efficiency of astronauts. Summarizing the effects of SF/SPE on gut microbiota may provide scientific basis for further researches in this field and the on-orbit health protection of astronauts.

Dietary Fiber and Its Potential Role in Obesity: A Focus on Modulating the Gut Microbiota

Dietary fiber is a carbohydrate polymer with ten or more monomeric units that are resistant to digestion by human digestive enzymes, and it has gained widespread attention due to its significant role in health improvement through regulating gut microbiota. In this review, we summarized the interaction between dietary fiber, gut microbiota, and obesity, and the beneficial effects of dietary fiber on obesity through the modulation of microbiota, such as modifying selective microbial composition, producing starch-degrading enzymes, improving gut barrier function, reducing the inflammatory response, reducing trimethylamine N-oxide, and promoting the production of gut microbial metabolites (e.g., short chain fatty acids, bile acids, ferulic acid, and succinate). In addition, factors affecting the gut microbiota composition and metabolites by dietary fiber (length of the chain, monosaccharide composition, glycosidic bonds) were also concluded. Moreover, strategies for enhancing the biological activity of dietary fiber (fermentation technology, ultrasonic modification, nanotechnology, and microfluidization) were subsequently discussed. This review may provide clues for deeply exploring the structure-activity relationship between dietary fiber and antiobesity properties by targeting specific gut microbiota.

Tryptophan-synthesizing bacteria enhance colonic motility

BACKGROUND

An emerging strategy to treat symptoms of gastrointestinal (GI) dysmotility utilizes the administration of isolated bacteria. However, the underlying mechanisms of action of these bacterial agents are not well established. Here, we elucidate a novel approach to promote intestinal motility by exploiting the biochemical capability of specific bacteria to produce the serotonin (5-HT) precursor, tryptophan (Trp).

METHODS

Mice were treated daily for 1 week by oral gavage of Bacillus (B.) subtilis (R0179), heat-inactivated R0179, or a tryptophan synthase-null strain of B. subtilis (1A2). Tissue levels of Trp, 5-HT, and 5-hydroxyindoleacetic acid (5-HIAA) were measured and changes in motility were evaluated.

KEY RESULTS

Mice treated with B. subtilis R0179 exhibited greater colonic tissue levels of Trp and the 5-HT breakdown product, 5-HIAA, compared to vehicle-treated mice. Furthermore, B. subtilis treatment accelerated colonic motility in both healthy mice as well as in a mouse model of constipation. These effects were not observed with heat-inactivated R0179 or the live 1A2 strain that does not express tryptophan synthase. Lastly, we found that the prokinetic effects of B. subtilis R0179 were blocked by coadministration of a 5-HT4 receptor (5-HT4 R) antagonist and were absent in 5-HT4 R knockout mice.

CONCLUSIONS AND INFERENCES

Taken together, these data demonstrate that intestinal motility can be augmented by treatment with bacteria that synthesize Trp, possibly through increased 5-HT signaling and/or actions of Trp metabolites, and involvement of the 5-HT4 R. Our findings provide mechanistic insight into a transient and predictable bacterial strategy to promote GI motility.

Asthma-protective agents in dust from traditional farm environments

BACKGROUND

Growing up on traditional European or US Amish dairy farms in close contact with cows and hay protects children against asthma, and airway administration of extracts from dust collected from cowsheds of those farms prevents allergic asthma in mice.

OBJECTIVES

This study sought to begin identifying farm-derived asthma-protective agents.

METHODS

Our work unfolded along 2 unbiased and independent but complementary discovery paths. Dust extracts (DEs) from protective and nonprotective farms (European and Amish cowsheds vs European sheep sheds) were analyzed by comparative nuclear magnetic resonance profiling and differential proteomics. Bioactivity-guided size fractionation focused on protective Amish cowshed DEs. Multiple in vitro and in vivo functional assays were used in both paths. Some of the proteins thus identified were characterized by in-solution and in-gel sodium dodecyl sulfate-polyacrylamide gel electrophoresis enzymatic digestion/peptide mapping followed by liquid chromatography/mass spectrometry. The cargo carried by these proteins was analyzed by untargeted liquid chromatography-high-resolution mass spectrometry.

RESULTS

Twelve carrier proteins of animal and plant origin, including the bovine lipocalins Bos d 2 and odorant binding protein, were enriched in DEs from protective European cowsheds. A potent asthma-protective fraction of Amish cowshed DEs (≈0.5% of the total carbon content of unfractionated extracts) contained 7 animal and plant proteins, including Bos d 2 and odorant binding protein loaded with fatty acid metabolites from plants, bacteria, and fungi.

CONCLUSIONS

Animals and plants from traditional farms produce proteins that transport hydrophobic microbial and plant metabolites. When delivered to mucosal surfaces, these agents might regulate airway responses.

Gut Microbiota and Respiratory Infections: Insights from Mendelian Randomization

The role of the gut microbiota in modulating the risk of respiratory infections has garnered increasing attention. However, conventional clinical trials have faced challenges in establishing the precise relationship between the two. In this study, we conducted a Mendelian randomization analysis with single nucleotide polymorphisms employed as instrumental variables to assess the causal links between the gut microbiota and respiratory infections. Two categories of bacteria, family Lactobacillaceae and genus Family XIII AD3011, were causally associated with the occurrence of upper respiratory tract infections (URTIs). Four categories of gut microbiota existed that were causally associated with lower respiratory tract infections (LRTIs), with order Bacillales and genus Paraprevotella showing a positive association and genus Alistipes and genus Ruminococcaceae UCG009 showing a negative association. The metabolites and metabolic pathways only played a role in the development of LRTIs, with the metabolite deoxycholine acting negatively and menaquinol 8 biosynthesis acting positively. The identification of specific bacterial populations, metabolites, and pathways may provide new clues for mechanism research concerning therapeutic interventions for respiratory infections. Future research should focus on elucidating the potential mechanisms regulating the gut microbiota and developing effective strategies to reduce the incidence of respiratory infections. These findings have the potential to significantly improve global respiratory health.

Antimicrobial Activity of Diffusible and Volatile Metabolites Emitted by Beauveria bassiana: Chemical Profile of Volatile Organic Compounds (VOCs) Using SPME-GC/MS Analysis

The genus Beauveria includes important entomopathogenic and endophytic fungi; among them, Beauveria bassiana is the most studied species. However, there is little knowledge regarding their antimicrobial activity. The current research has been conducted to evaluate the in vitro antagonistic activity of B. bassiana and the antimicrobial efficacy of its Exo and Endo metabolites against Bacillus cereus, B. megaterium, Clavibacter michiganensis (Gram positive bacteria, G+ve), Xanthomonas campestris, Pseudomonas aeruginosa and P. fluorescence (Gram negative bacteria, G-ve). In addition, solid-phase microextraction (SPME) was coupled with Gas Chromatography-Mass Spectrometry (GC/MS) to qualitatively measure the volatile organic compounds' (VOCs) metabolic profile of the most efficient studied isolate of B. bassiana. The obtained results showed that the isolate UniB2439-3 has a promising antibacterial effect against most of the studied target bacteria. An SPME-GC/MS analysis of VOCs revealed the presence of ethanol, butanal,2-methyl, 2,4-dimethyl-1-heptene, octane, 4-methyl and β-elemene as the dominant bioactive compounds. The results demonstrated that the efficient isolate of B. bassiana can be potentially used as a biocontrol agent against several bacteria, especially G+ve ones.

Investigating the disease-modifying properties of sclerotiorin in Alzheimer's therapy using acetylcholinesterase inhibition

Alzheimer's disease (AD) is a progressive neurodegenerative disorder caused due to the damage and loss of neurons in specific brain regions. It is the most common form of dementia observed in older people. The symptoms start with memory loss and gradually cause the inability to speak and do day-to-day activities. The cost of caring for those affected individuals is huge and is probably beyond most developing countries capability. Current pharmacotherapy for AD includes compounds that aim to increase neurotransmitters at nerve endings. This can be achieved by cholinergic neurotransmission through inhibition of the cholinesterase enzyme. The current research aims to find natural substances that can be used as drugs to treat AD. The present work identifies and explains compounds with considerable Acetylcholinesterase (AChE) inhibitory activities. The pigment was extracted from the Penicillium mallochii ARA1 (MT373688.1) strain using ethyl acetate, and the active compound was identified using chromatographic techniques followed by structural confirmation with NMR. AChE inhibition experiments, enzyme kinetics, and molecular dynamics simulation studies were done to explain the pharmacological and pharmacodynamic properties. We identified that the compound sclerotiorin in the pigment has AChE inhibitory activity. The compound is stable and can bind to the enzyme non-competitively. Sclerotiorin obeys all the drug-likeliness parameters and can be developed as a promising drug in treating AD.

Alcohol, the gut microbiome, and liver disease

The microorganisms inhabiting our gastrointestinal tract are critical for human health. Chronic heavy alcohol use can modulate the composition and function of the gut microbiota, thereby exacerbating end-organ damage via the gut-brain axis and the gut-liver axis. In this review, we summarize the bacterial, fungal, and viral gut microbial compositional changes associated with alcohol use and alcohol-associated liver disease and discuss the mechanisms of action by which gut dysbiosis reinforces alcohol use behavior and liver inflammation and injury. We also highlight important pre-clinical and clinical trials that target gut microbial-specific mechanisms for the treatment of alcohol use disorder and alcohol-associated liver disease.

The roles of gut microbiota and its metabolites in diabetic nephropathy

Diabetic nephropathy (DN) is a severe microvascular complication of diabetes, which increases the risk of renal failure and causes a high global disease burden. Due to the lack of sustainable treatment, DN has become the primary cause of end-stage renal disease worldwide. Gut microbiota and its metabolites exert critical regulatory functions in maintaining host health and are associated with many pathogenesis of aging-related chronic diseases. Currently, the theory gut-kidney axis has opened a novel angle to understand the relationship between gut microbiota and multiple kidney diseases. In recent years, accumulating evidence has revealed that the gut microbiota and their metabolites play an essential role in the pathophysiologic processes of DN through the gut-kidney axis. In this review, we summarize the current investigations of gut microbiota and microbial metabolites involvement in the progression of DN, and further discuss the potential gut microbiota-targeted therapeutic approaches for DN.

Microbiota-produced indole metabolites disrupt mitochondrial function and inhibit Cryptosporidium parvum growth

Cryptosporidiosis is a leading cause of life-threatening diarrhea in young children in resource-poor settings. To explore microbial influences on susceptibility, we screened 85 microbiota-associated metabolites for their effects on Cryptosporidium parvum growth in vitro. We identify eight inhibitory metabolites in three main classes: secondary bile salts/acids, a vitamin B6 precursor, and indoles. Growth restriction of C. parvum by indoles does not depend on the host aryl hydrocarbon receptor (AhR) pathway. Instead, treatment impairs host mitochondrial function and reduces total cellular ATP, as well as directly reducing the membrane potential in the parasite mitosome, a degenerate mitochondria. Oral administration of indoles, or reconstitution of the gut microbiota with indole-producing bacteria, delays life cycle progression of the parasite in vitro and reduces the severity of C. parvum infection in mice. Collectively, these findings indicate that microbiota metabolites impair mitochondrial function and contribute to colonization resistance to Cryptosporidium infection.

Gut Microbiota and its Metabolites: Bridge of Dietary Nutrients and Alzheimer's Disease

Alzheimer's disease (AD) is a neurodegenerative disease characterized by progressive cognitive impairment and neuroinflammation. Recent research has revealed the crucial role of gut microbiota and microbial metabolites in modulating AD. However, the mechanisms by which the microbiome and microbial metabolites affect brain function remain poorly understood. Here, we review the literature on changes in the diversity and composition of the gut microbiome in patients with AD and in animal models of AD. We also discuss the latest progress in understanding the pathways by which the gut microbiota and microbial metabolites from the host or diet regulate AD. By understanding the effects of dietary components on brain function, microbiota composition, and microbial metabolites, we examine the potential for manipulation of the gut microbiota through dietary intervention to delay the progression of AD. Although it is challenging to translate our understanding of microbiome-based approaches to dietary guidelines or clinical therapies, these findings provide an attractive target for promoting brain function.

The role of the gut microbiota in gastric cancer: the immunoregulation and immunotherapy

Gastric cancer (GC) is one of the most common cancers, leading to the deaths of millions of people worldwide. Therefore, early detection and effective therapeutic strategies are of great value for decreasing the occurrence of advanced GC. The human microbiota is involved not only in the maintenance of physiological conditions, but also in human diseases such as obesity, diabetes, allergic and atopic diseases, and cancer. Currently, the composition of the bacteria in the host, their functions, and their influence on disease progression and treatment are being discussed. Previous studies on the gut microbiome have mostly focused on Helicobacter pylori (Hp) owing to its significant role in the development of GC. Nevertheless, the enrichment and diversity of other bacteria that can modulate the tumor microenvironment are involved in the progression of GC and the efficacy of immunotherapy. This review provides systematic insight into the components of the gut microbiota and their application in GC, including the specific bacteria of GC, their immunoregulatory effect, and their diagnostic value. Furthermore, we discuss the relationship between the metabolism of microbes and their potential applications, which may serve as a new approach for the diagnosis and treatment of GC.

Promising Markers of Inflammatory and Gut Dysbiosis in Patients with Post-COVID-19 Syndrome

Post-COVID-19 syndrome is a complex of different symptoms, which results in a multisystemic impairment after the suffering from COVID-19 infection. The aim of the study was to reveal the clinical, laboratory, and gut disorders in patients with post-COVID-19 syndrome (n = 39) before and after taking part in the 14-day complex program of rehabilitation. A complete blood count, coagulation test, blood chemistry, biomarkers, and metabolites in serum samples, and gut dysbiosis were revealed in patients on the day of admission and after 14-day rehabilitation, in comparison with the variables of healthy volunteers (n = 48) or with reference ranges. On the day of discharge, patients noted an improvement in respiratory function, general well-being, and mood. At the same time, the levels of some metabolic (4-hydroxybenzoic, succinic, fumaric acids) and inflammatory (interleukin-6) variables, which were increased on admission, did not reach the level of healthy people during the rehabilitation program. Taxonomy disbalance was observed in patients' feces, namely, a high level of total bacterial mass, a decrease in the number of Lactobacillus spp., and an increase in pro-inflammatory microorganisms. The authors suggest that the post-COVID-19 rehabilitation program should be personalized, considering the patient's state together with not only the baseline levels of biomarkers, but also with the individual taxonomy of the gut microbiota.

Potential role of gut microbiota in prostate cancer: immunity, metabolites, pathways of action?

The gut microbiota helps to reveal the relationship between diseases, but the role of gut microbiota in prostate cancer (PCa) is still unclear. Recent studies have found that the composition and abundance of specific gut microbiota are significantly different between PCa and non-PCa, and the gut microbiota may have common and unique characteristics between different diseases. Intestinal microorganisms are affected by various factors and interact with the host in a variety of ways. In the complex interaction model, the regulation of intestinal microbial metabolites and the host immune system is particularly important, and they play a key role in maintaining the ecological balance of intestinal microorganisms and metabolites. However, specific changes in the composition of intestinal microflora may promote intestinal mucosal immune imbalance, leading to the formation of tumors. Therefore, this review analyzes the immune regulation of intestinal flora and the production of metabolites, as well as their effects and mechanisms on tumors, and briefly summarizes that specific intestinal flora can play an indirect role in PCa through their metabolites, genes, immunity, and pharmacology, and directly participate in the occurrence, development, and treatment of tumors through bacterial and toxin translocation. We also discussed markers of high risk PCa for intestinal microbiota screening and the possibility of probiotic ingestion and fecal microbiota transplantation, in order to provide better treatment options for clinic patients. Finally, after summarizing a number of studies, we found that changes in immunity, metabolites.

Gut Microbial Metabolite Butyrate and Its Therapeutic Role in Inflammatory Bowel Disease: A Literature Review

Background and objective: Inflammatory bowel disease (IBD), including Crohn's disease and ulcerative colitis, is a chronic inflammatory disorder characterized by aberrant immune responses and compromised barrier function in the gastrointestinal tract. IBD is associated with altered gut microbiota and their metabolites in the colon. Butyrate, a gut microbial metabolite, plays a crucial role in regulating immune function, epithelial barrier function, and intestinal homeostasis. In this review, we aim to present an overview of butyrate synthesis and metabolism and the mechanism of action of butyrate in maintaining intestinal homeostasis and to discuss the therapeutic implications of butyrate in IBD. Methods: We searched the literature up to March 2023 through PubMed, Web of Science, and other sources using search terms such as butyrate, inflammation, IBD, Crohn's disease, and ulcerative colitis. Clinical studies in patients and preclinical studies in rodent models of IBD were included in the summary of the therapeutic implications of butyrate. Results: Research in the last two decades has shown the beneficial effects of butyrate on gut immune function and epithelial barrier function. Most of the preclinical and clinical studies have shown the positive effect of butyrate oral supplements in reducing inflammation and maintaining remission in colitis animal models and IBD patients. However, butyrate enema showed mixed effects. Butyrogenic diets, including germinated barley foodstuff and oat bran, are found to increase fecal butyrate concentrations and reduce the disease activity index in both animal models and IBD patients. Conclusions: The current literature suggests that butyrate is a potential add-on therapy to reduce inflammation and maintain IBD remission. Further clinical studies are needed to determine if butyrate administration alone is an effective therapeutic treatment for IBD.

Microbial metabolites in chronic heart failure and its common comorbidities

This study aimed to identify microbial signatures that contribute to the shared etiologies between chronic heart failure (CHF), type 2 diabetes, and chronic kidney disease. The serum levels of 151 microbial metabolites were measured in 260 individuals from the Risk Evaluation and Management of heart failure cohort, and it was found that those metabolites varied by an order of 10⁵ fold. Out of 96 metabolites associated with the three cardiometabolic diseases, most were validated in two geographically independent cohorts. In all three cohorts, 16 metabolites including imidazole propionate (ImP) consistently showed significant differences. Notably, baseline ImP levels were three times higher in the Chinese compared with the Swedish cohorts and increased by 1.1-1.6 fold with each additional CHF comorbidity in the Chinese population. Cellular experiments further supported a causal link between ImP and distinct CHF relevant phenotypes. Additionally, key microbial metabolite-based risk scores were superior in CHF prognosis than the traditional Framingham or Get with the Guidelines-Heart Failure risk scores. Interactive visualization of these specific metabolite-disease links is available on our omics data server (https://omicsdata.org/Apps/REM-HF/).

Chemical Identification of Secondary Metabolites from Rhizospheric Actinomycetes Using LC-MS Analysis: In Silico Antifungal Evaluation and Growth-Promoting Effects

The rhizosphere is a rich source of actinomycetes which can produce several potential biologically active secondary metabolites. The principal goal for this research is to extract, purify, and characterize the bioactive secondary metabolites produced by three different strains of actinomycetes isolated from the rhizosphere of rosemary, black locust, and olive. The plant growth-promoting effect (PGPE) of the studied strains of actinomycetes on Ocimum basilicum L. (basil) and the disease-control effect on necrotic stem lesions of "black leg" caused by Fusarium tabacinum on basil were evaluated in silico. The cell-free culture filtrates from the studied actinomycetes isolates were evaluated in vitro for their antimicrobial activity against some common phytopathogens. The secondary metabolites obtained from the cell-free culture filtrates have been chemically characterized using high-resolution electrospray ionization of liquid-chromatography/mass-spectrometric detection (ESI-(HR)Orbitrap-MS). Results of the in silico trial showed that all studied isolates demonstrated PGPE on basil seedlings, improved some eco-physiological characteristics, and reduced the disease incidence of F. tabacinum. The extracted metabolites from the studied actinomycetes demonstrated antimicrobial activity in a Petri-plates assay. The chemical analysis revealed the presence of 20 different components. This research emphasizes how valuable the examined isolates are for producing bioactive compounds, indicating their putative antimicrobial activity and their potential employment as fungal biocontrol agents. In particular, the obtained results revealed the possibility of green synthesis of some important secondary metabolites, such as N-Acetyl-l-histidinol, Rhizocticin A, and Eponemycin, from actinomycetes. The bioactive metabolites may be successively used to develop novel bio-formulations for both crop protection and/or PGPE.

Prebiotic and Probiotic Modulation of the Microbiota-Gut-Brain Axis in Depression

Emerging evidence demonstrates that alterations to the gut microbiota can affect mood, suggesting that the microbiota-gut-brain (MGB) axis contributes to the pathogenesis of depression. Many of these pathways overlap with the way in which the gut microbiota are thought to contribute to metabolic disease progression and obesity. In rodents, prebiotics and probiotics have been shown to modulate the composition and function of the gut microbiota. Together with germ-free rodent models, probiotics have provided compelling evidence for a causal relationship between microbes, microbial metabolites, and altered neurochemical signalling and inflammatory pathways in the brain. In humans, probiotic supplementation has demonstrated modest antidepressant effects in individuals with depressive symptoms, though more studies in clinically relevant populations are needed. This review critically discusses the role of the MGB axis in depression pathophysiology, integrating preclinical and clinical evidence, as well as the putative routes of communication between the microbiota-gut interface and the brain. A critical overview of the current approaches to investigating microbiome changes in depression is provided. To effectively translate preclinical breakthroughs in MGB axis research into novel therapies, rigorous placebo-controlled trials alongside a mechanistic and biochemical understanding of prebiotic and probiotic action are required from future research.

Gut microbiota promote liver regeneration through hepatic membrane phospholipid biosynthesis

BACKGROUND & AIMS

Hepatocyte growth and proliferation depends on membrane phospholipid biosynthesis. Short-chain fatty acids (SCFAs) generated by bacterial fermentation, delivered through the gut-liver axis, significantly contribute to lipid biosynthesis. We therefore hypothesized that dysbiotic insults like antibiotic treatment not only affect gut microbiota, but also impair hepatic lipid synthesis and liver regeneration.

METHODS

Stable isotope labeling and 70% partial hepatectomy (PHx) was carried out in C57Bl/6J wild-type mice, in mice treated with broad-spectrum antibiotics, in germ-free mice and mice colonized with minimal microbiota. The microbiome was analyzed by 16S rRNA gene sequencing and microbial culture. Gut content, liver, blood and primary hepatocyte organoids were tested by mass spectrometry-based lipidomics, quantitative reverse-transcription PCR (qRT-PCR), immunoblot and immunohistochemistry for expression of proliferative and lipogenic markers. Matched biopsies from hyperplastic and hypoplastic liver tissue of patients subjected to surgical intervention to induce hyperplasia were analyzed by qRT-PCR for lipogenic enzymes.

RESULTS

Three days of antibiotic treatment induced persistent dysbiosis with significantly decreased beta-diversity and richness, but a massive increase of Proteobacteria, accompanied by decreased colonic SCFAs. After PHx, antibiotic-treated mice showed delayed liver regeneration, increased mortality, impaired hepatocyte proliferation and decreased hepatic phospholipid synthesis. Expression of the lipogenic enzyme SCD1 was upregulated after PHx but delayed by antibiotic treatment. Germ-free mice essentially recapitulated the phenotype of antibiotic treatment. Phospholipid biosynthesis, hepatocyte proliferation, liver regeneration and survival were rescued in gnotobiotic mice colonized with a minimal SCFA-producing microbial community. SCFAs induced the growth of murine hepatocyte organoids and hepatic SCD1 expression in mice. Further, SCD1 was required for proliferation of human hepatoma cells and was associated with liver regeneration in human patients.

CONCLUSION

Gut microbiota are pivotal for hepatic membrane phospholipid biosynthesis and liver regeneration.

IMPACT AND IMPLICATIONS

Gut microbiota affect hepatic lipid metabolism through the gut-liver axis, but the underlying mechanisms are poorly understood. Perturbations of the gut microbiome, e.g. by antibiotics, impair the production of bacterial metabolites, which normally serve as building blocks for membrane lipids in liver cells. As a consequence, liver regeneration and survival after liver surgery is severely impaired. Even though this study is preclinical, its results might allow physicians in the future to improve patient outcomes after liver surgery, by modulation of gut microbiota or their metabolites.

Mechanisms of Maternal Diet-Induced Obesity Affecting the Offspring Brain and Development of Affective Disorders

Depression and metabolic disease are common disorders that share a bidirectional relationship and continue to increase in prevalence. Maternal diet and maternal behaviour both profoundly influence the developmental trajectory of offspring during the perinatal period. At an epidemiological level, both maternal depression and obesity during pregnancy have been shown to increase the risk of neuropsychiatric disease in the subsequent generation. Considerable progress has been made to understand the mechanisms by which maternal obesity disrupts the developing offspring gut-brain axis, priming offspring for the development of affective disorders. This review outlines such mechanisms in detail, including altered maternal care, the maternal microbiome, inflammation, breast milk composition, and maternal and placental metabolites. Subsequently, offspring may be prone to developing gut-brain interaction disorders with concomitant changes to brain energy metabolism, neurotransmission, and behaviour, alongside gut dysbiosis. The gut microbiome may act as a key modifiable, and therefore treatable, feature of the relationship between maternal obesity and the offspring brain function. Further studies examining the relationship between maternal nutrition, the maternal microbiome and metabolites, and offspring neurodevelopment are warranted to identify novel therapeutic targets.

Influence of the gut microbiota on satiety signaling

Recent studies show a link between the gut microbiota and the regulation of satiety and energy intake, processes that contribute to the development and pathophysiology of metabolic diseases. However, this link is predominantly established in animal and in vitro studies, whereas human intervention studies are scarce. In this review we focus on recent evidence linking satiety and the gut microbiome, with specific emphasis on gut microbial short-chain fatty acids (SCFAs). Based on a systematic search we provide an overview of human studies linking the intake of prebiotics with gut microbial alterations and satiety signaling. Our outcomes highlight the importance of in-depth examination of the gut microbiota in relation to satiety and provide insights into recent and future studies in this field.

Aryl Hydrocarbon Receptor Agonism Antagonizes the Hypoxia-driven Inflammation in Cystic Fibrosis

Hypoxia contributes to the exaggerated yet ineffective airway inflammation that fails to oppose infections in cystic fibrosis (CF). However, the potential for impairment of essential immune functions by HIF-1α (hypoxia-inducible factor 1α) inhibition demands a better comprehension of downstream hypoxia-dependent pathways that are amenable for manipulation. We assessed here whether hypoxia may interfere with the activity of AhR (aryl hydrocarbon receptor), a versatile environmental sensor highly expressed in the lungs, where it plays a homeostatic role. We used murine models of Aspergillus fumigatus infection in vivo and human cells in vitro to define the functional role of AhR in CF, evaluate the impact of hypoxia on AhR expression and activity, and assess whether AhR agonism may antagonize hypoxia-driven inflammation. We demonstrated that there is an important interferential cross-talk between the AhR and HIF-1α signaling pathways in murine and human CF, in that HIF-1α induction squelched the normal AhR response through an impaired formation of the AhR:ARNT (aryl hydrocarbon receptor nuclear translocator)/HIF-1β heterodimer. However, functional studies and analysis of the AhR genetic variability in patients with CF proved that AhR agonism could prevent hypoxia-driven inflammation, restore immune homeostasis, and improve lung function. This study emphasizes the contribution of environmental factors, such as infections, in CF disease progression and suggests the exploitation of hypoxia:xenobiotic receptor cross-talk for antiinflammatory therapy in CF.

The Human Respiratory Microbiome: Current Understandings and Future Directions

Microorganisms colonize the human body. The lungs and respiratory tract, previously believed to be sterile, harbor diverse microbial communities and the genomes of bacteria (bacteriome), viruses (virome), and fungi (mycobiome). Recent advances in amplicon and shotgun metagenomic sequencing technologies and data-analyzing methods have greatly aided the identification and characterization of microbial populations from airways. The respiratory microbiome has been shown to play roles in human health and disease and is an area of rapidly emerging interest in pulmonary medicine. In this review, we provide updated information in the field by focusing on four lung conditions, including asthma, chronic obstructive pulmonary disease, cystic fibrosis, and idiopathic pulmonary fibrosis. We evaluate gut, oral, and upper airway microbiomes and how they contribute to lower airway flora. The discussion is followed by a systematic review of the lower airway microbiome in health and disease. We conclude with promising research avenues and implications for evolving therapeutics.

In silico analysis of dietary polyphenols and their gut microbial metabolites suggest inhibition of SARS-CoV-2 infection, replication, and host inflammatory mediators

The outcome of SARS-CoV-2 infection ranges from asymptomatic to severe COVID-19 and death resulting from an exaggerated immune response termed cytokine storm. Epidemiological data have associated consumption of a high-quality plant-based diet with decreased incidence and severity of COVID-19. Dietary polyphenols and their microbial metabolites (MMs) have anti-viral and anti-inflammatory activities. Autodock Vina and Yasara were used in molecular docking and dynamics studies to investigate potential interactions of 7 parent polyphenols (PPs) and 11 MMs with the α- and Omicron variants of the SARS-CoV-2 spike glycoprotein (SGP), papain-like pro-tease (PLpro) and 3 chymotrypsin-like protease (3CLpro), as well as host inflammatory mediators including complement component 5a (C5a), C5a receptor (C5aR), and C-C chemokine receptor type 5 (CCR5). PPs and MMs interacted to varying degrees with residues on target viral and host inflammatory proteins showing potential as competitive inhibitors. Based on these in silico findings, PPs and MMs may inhibit SARS-CoV-2 infection, replication, and/or modulate host immunity in the gut or periphery. Such inhibition may explain why people that consume a high-quality plant-based diet have less incidence and severity of COVID-19.Communicated by Ramaswamy H. Sarma.

Butyrate Differentiates Permissiveness to Clostridioides difficile Infection and Influences Growth of Diverse C. difficile Isolates

A disrupted "dysbiotic" gut microbiome engenders susceptibility to the diarrheal pathogen Clostridioides difficile by impacting the metabolic milieu of the gut. Diet, in particular the microbiota-accessible carbohydrates (MACs) found in dietary fiber, is one of the most powerful ways to affect the composition and metabolic output of the gut microbiome. As such, diet is a powerful tool for understanding the biology of C. difficile and for developing alternative approaches for coping with this pathogen. One prominent class of metabolites produced by the gut microbiome is short-chain fatty acids (SCFAs), the major metabolic end products of MAC metabolism. SCFAs are known to decrease the fitness of C. difficile in vitro, and high intestinal SCFA concentrations are associated with reduced fitness of C. difficile in animal models of C. difficile infection (CDI). Here, we use controlled dietary conditions (8 diets that differ only by MAC composition) to show that C. difficile fitness is most consistently impacted by butyrate, rather than the other two prominent SCFAs (acetate and propionate), during murine model CDI. We similarly show that butyrate concentrations are lower in fecal samples from humans with CDI than in those from healthy controls. Finally, we demonstrate that butyrate impacts growth in diverse C. difficile isolates. These findings provide a foundation for future work which will dissect how butyrate directly impacts C. difficile fitness and will lead to the development of diverse approaches distinct from antibiotics or fecal transplant, such as dietary interventions, for mitigating CDI in at-risk human populations. IMPORTANCE Clostridioides difficile is a leading cause of infectious diarrhea in humans, and it imposes a tremendous burden on the health care system. Current treatments for C. difficile infection (CDI) include antibiotics and fecal microbiota transplant, which contribute to recurrent CDIs and face major regulatory hurdles, respectively. Therefore, there is an ongoing need to develop new ways to cope with CDI. Notably, a disrupted "dysbiotic" gut microbiota is the primary risk factor for CDI, but we incompletely understand how a healthy microbiota resists CDI. Here, we show that a specific molecule produced by the gut microbiota, butyrate, is negatively associated with C. difficile burdens in humans and in a mouse model of CDI and that butyrate impedes the growth of diverse C. difficile strains in pure culture. These findings help to build a foundation for designing alternative, possibly diet-based, strategies for mitigating CDI in humans.