Search Results (2,953)

Alzheimer’s disease (AD) is a progressive neurodegenerative disorder with a complex etiology whose exact mechanisms are not fully understood. In recent years, there has been growing interest in the role of the gastrointestinal microbiota in the pathogenesis of AD, particularly in the context of the gut–brain axis. The purpose of this review is to discuss the current state of knowledge regarding potential relationships between the composition of the gut microbiota and the development and progression of AD. Preclinical and clinical studies indicating that microbiota imbalances (dysbiosis) may contribute to increased inflammation, increased permeability of the intestinal and blood–brain barriers, and accumulation of pathological proteins such as beta-amyloid and tau are analyzed. The effects of diet, probiotics and microbiota interventions on cognitive function were also discussed. An attempt was also made to evaluate microbiota disruption as a potential early marker of AD development. Although the mechanisms require further study, the role of the gut microbiota appears to be an important and promising direction in understanding the pathophysiology of AD and developing potential therapeutic and diagnostic strategies. Full article

Obsessive–compulsive disorder (OCD) is a multifactorial condition, and interest in gut–brain interactions is increasing. We conducted a systematic two-step review, registered in PROSPERO (CRD420251083936). Step 1 mapped core OCD biology to gut-relevant pathways, including neuroimmune activation, epithelial barrier function, microbial metabolites, and stress circuitry, to clarify plausible mechanisms. Step 2 synthesized evidence from human and preclinical studies that measured or manipulated microbiota. Searches across PubMed, EMBASE, Web of Science, PsycINFO, and Cochrane (September 2025) yielded 357 biological and 20 microbiota-focused studies. Risk of bias was assessed using the Joanna Briggs Institute checklist for human studies and SYRCLE’s tool for animal studies. Although taxonomic findings in human cohorts were heterogeneous, functional patterns converged: reduced short-chain fatty acid capacity, enrichment of pro-inflammatory pathways, and host markers of barrier disruption and inflammation correlating with OCD severity. Transferring patient microbiota to mice induced OCD-like behaviors with neuroinflammatory changes, partly rescued by metabolites or barrier-supporting strains. Mendelian randomization suggested possible causal contributions at higher taxonomic levels. Diet, especially fiber intake, and psychotropic exposure were major sources of heterogeneity. Evidence supports the microbiota as a modifiable co-factor in a subset of OCD, motivating diet-controlled, stratified clinical trials with composite host–microbe endpoints. Full article

Zeolites are ‘magic stones’ with crystalline structures and unique properties, which enable them to selectively adsorb molecules, including gases. The aim of the study was to determine the effect of different types and doses of zeolites on microorganisms, nutrient digestion, and methane production in the rumen. The study was conducted on five two-year-old Jersey heifers (350 kg live weight) fistulated to the rumen in a 5 × 5 Latin square design divided into five feeding groups: control (basal diet), ZN2 (+120 g clinoptilolite/d), ZS2 (+120 g ZP-4A zeolite/d), ZN4 (+240 g clinoptilolite/d), and ZS4 (+240 g ZP-4A zeolite/d). During five periods of the experiment, the samples of the ruminal fluid and digesta were taken before and 3 h after feeding. The pH value, bacteria and methanogens populations, as well as short-chain fatty acids (SCFAs) and methane production in the rumen were not affected after zeolite addition (p > 0.05). ZN2 diet decreased the number of total protozoa by 41.2% (p = 0.023) and Entodinium spp. by 51.1% (p = 0.021), while ZS2, ZN4, and ZS4 diets reduced Diplodinium population by 70.5% (p < 0.001) 3 h after feeding in comparison to the control diet. An increased population of Ophryoscolex spp. was noted in ZN2 and ZS4 cow 3 h after feeding (p < 0.001; 0.15 × 10⁴/mL and 0.08 × 10⁴/mL vs. 0.02 × 10⁴/mL) when compared to control animals. Furthermore, ZS4 diet increased ammonia (p = 0.007; 3.97 mM/L vs. 2.27 mM/L), tryptamine (p = 0.014; 0.009 µmol/g vs. 0.007 µmol/g) and 1.7-diaminoheptane (p < 0.001; 0.016 µmol/g vs. 0.006 µmol/g) concentrations in the rumen, while phenylethylamine level was 90.9% higher in ZN4 cows (p = 0.007), in comparison to control, depending on time. To summarise, zeolites may act in a type- and dose-dependent manner on the protozoa population and indicators of protein degradation. Full article

Herbivorous animals rely on complex gastrointestinal systems and microbial communities to efficiently digest plant-based diets, extract nutrients, and maintain health. Recent advances in metagenomic technologies have enabled high-resolution, culture-independent analysis of gut microbiota composition, functional potential, and host–microbe interactions, providing insights into microbial diversity across the herbivore digestive tract. This review summarizes key findings on the gastrointestinal microbiota of herbivores, focusing on ruminant foregut and non-ruminant hindgut fermentation. Ruminants like cattle, sheep, and goats host microbiota enriched with fibrolytic and methanogenic microbes that facilitate fiber degradation and volatile fatty acid production, contributing significantly to energy balance. In contrast, non-ruminants such as horses and rabbits rely on hindgut fermentation, with distinct microbial taxa contributing to carbohydrate and protein breakdown. The review further explores how specific microbial taxa, including Prevotella, Fibrobacter, and Ruminococcus, correlate with improved feed efficiency and growth performance, particularly in ruminants. Additionally, the roles of probiotics, prebiotics, and symbiotics in modulating gut microbial composition and enhancing productivity are discussed. Despite significant advances, challenges remain in microbial sampling, functional annotation, and understanding the integration of microbiota with host physiology. The review emphasizes the potential of metagenomic insights in optimizing herbivore gut microbiota to improve feed efficiency, health, and sustainable livestock production. Full article

The human gut microbiota helps maintain metabolic balance, supports immune function, and defends against opportunistic pathogens that can disrupt the microbiota ecosystem. An imbalance or dysbiosis in microbial composition is linked to various diseases, including inflammatory bowel disease, metabolic syndromes, and neurodegenerative disorders. Using microbiota modulation with prebiotics and postbiotics is a practical approach to address these imbalances. Prebiotic compounds are defined as substrates that promote metabolic activity and restore microbial patterns. Postbiotics include short-chain fatty acids (SCFAs), microbial cell lysates, and extracellular compounds. This research aims to investigate how the gut microbiota can be modulated in vitro using the prebiotic ColonX and a postbiotic derived from Kombucha fermentation within a controlled GIS1 in vitro system. These products demonstrate potential for modulation, as they support selective bacterial growth and enhance microbial diversity. Prebiotics help stabilize gut pH, while postbiotics play a crucial role in biofilm formation. Together, they provide an innovative approach to treating dysbiosis and enhancing overall gut health. The findings highlight the importance of utilizing prebiotics and postbiotics to modulate gut microbiota in chronic diseases characterized by dysbiosis. This paper is especially relevant for elderly populations, as gut dysbiosis is common, and microbiota modulation supports healthy aging. Full article

Background/Objectives: The interplay between host metabolism and gut microbiota is central to the pathophysiology of metabolic diseases, including metabolic dysfunction-associated steatotic liver disease (MASLD). In this study, we investigated the underexplored fecal host–microbiota co-metabolism profile of male and female Wistar rats after 21 weeks of high-fat diet (HFD), a model previously validated for early MASLD. Methods: Using ¹H-NMR spectroscopy, we detected and quantified metabolites in fecal samples associated with hepatic metabolism beyond short-chain fatty acids (SCFAs), such as energy-related metabolites, amino acid turnover, branched-chain amino acid (BCAA) catabolism, and microbial fermentation. Results: Distinct metabolic signatures were identified according to diet and sex, and statistical analysis was performed. Notably, alterations were observed in bile acids (BAs) such as cholate and glycocholate, suggesting disruptions in enterohepatic circulation. The presence of fucose, a sugar linked to liver pathology, was also elevated. Energy-related metabolites indicated a shift from lactate production to increased acetoacetate and malonate levels, implying redirection of pyruvate metabolism and inhibition of the TCA cycle. BCAA derivatives such as 3-methyl-2-oxovalerate and 3-aminoisobutyrate were altered, supporting earlier findings on disrupted amino acid metabolism under HFD conditions. Furthermore, microbial metabolites including methanol and ethanol showed group-specific differences, suggesting shifts in microbial activity. Conclusions: These findings complement previous longitudinal data and provide a functional interpretation of newly identified metabolites. These metabolites, previously unreported, are now functionally contextualized and linked to hepatic and microbial dysregulation, offering novel biological insights into early MASLD mechanisms. Full article

The gut microbiome possesses a diverse range of biological properties that play a role in maintaining host health and preventing disease. Gut microbial metabolites, including short-chain fatty acids, natural purine nucleosides, ellagic acid derivatives, and tryptophan metabolites, have been observed to have complex and multifaceted roles in the gut and in wider body systems in the management of disease, including cancer. Triple-negative breast cancer is the most aggressive subtype of breast cancer, with restricted treatment options and poor prognoses. Recently, preclinical research has investigated the antiproliferative potential of gut microbial metabolites against this type of breast cancer with promising results. However, little is understood about the mechanisms of action and molecular pathways driving this antiproliferative potential. Understanding the complex mechanisms of action of gut microbial metabolites on triple-negative breast cancer will be instrumental in the investigation of the combined administration with standard chemotherapeutic drugs. To date, there is a paucity of research studies investigating the potential synergistic interactions between gut microbial metabolites and standard chemotherapeutic drugs. The identification of synergistic potential between these compounds may provide alternate and more effective therapeutic options in the treatment and management of triple-negative breast cancer. Further investigation into the mechanistic action of gut microbial metabolites against this breast cancer subtype may support the administration of more cost-effective treatment options for breast cancer, with an aim to reduce side effects associated with standard treatments. Additionally, future research will aim to identify more potent metabolite–drug combinations in the mitigation of triple-negative breast cancer progression and metastasis. Full article

The Mongolian wild ass (Equus hemionus hemionus) is a flagship species of the desert-steppe ecosystem in Asia, and understanding its strategies for coping with cold environments is vital for both revealing its survival mechanisms and informing conservation efforts. In this study, we employed metagenomic sequencing to characterize the composition and functional potential of the gut microbiota, and applied DNA metabarcoding of the chloroplast trnL (UAA) g–h fragment to analyze dietary composition, aiming to reveal seasonal variations and the interplay between dietary plant composition and gut microbial communities. In the cold season, Bacteroidota and Euryarchaeota were significantly enriched, suggesting enhanced fiber degradation and energy extraction from low-quality forage. Moreover, genera such as Bacteroides and Alistipes were also significantly enriched and associated with short-chain fatty acid (SCFA) metabolism, bile acid tolerance, and immune modulation. In the cold season, higher Simpson index values and tighter principal coordinates analysis (PCoA) clustering indicated a more diverse and stable microbiota under harsh environmental conditions, which may represent an important microecological strategy for the host to cope with extreme environments. Functional predictions based on the Kyoto Encyclopedia of Genes and Genomes (KEGG) further indicated upregulation of metabolic and signaling pathways, including ABC transporters, two-component systems, and quorum sensing, suggesting multi-level microbial responses to low temperatures and nutritional stress. trnL-based plant composition analysis indicated seasonal shifts, with Tamaricaceae detected more in the warm season and Poaceae, Chenopodiaceae, and Amaryllidaceae detected more in the cold season. Correlation analyses revealed that dominant microbial phyla were associated with the degradation of fiber, polysaccharides, and plant secondary metabolites, which may help maintain host energy and metabolic homeostasis. Despite the limited sample size and cross-sectional design, our findings highlight that gut microbial composition and structure may be important for host adaptation to cold environments and may also serve as a useful reference for future studies on the adaptive mechanisms and conservation strategies of endangered herbivores, including the Mongolian wild ass. Full article

Bone immunity represents a dynamic interface where skeletal homeostasis intersects with systemic immune regulation. We synthesize emerging paradigms by contrasting two functionally distinct microenvironments: the marrow cavity, a hematopoietic and immune cell reservoir, and cancellous bone, a metabolically active hub orchestrating osteoimmune interactions. The marrow cavity not only generates innate and adaptive immune cells but also preserves long-term immune memory through stromal-derived chemokines and survival factors, while cancellous bone regulates bone remodeling via macrophage-osteoclast crosstalk and cytokine gradients. Breakthroughs in lymphatic vasculature identification challenge traditional views, revealing cortical and lymphatic networks in cancellous bone that mediate immune surveillance and pathological processes such as cancer metastasis. Central to bone immunity is the neuro–immune–endocrine axis, where sympathetic and parasympathetic signaling bidirectionally modulate osteoclastogenesis and macrophage polarization. Gut microbiota-derived metabolites, including short-chain fatty acids and polyamines, reshape bone immunity through epigenetic and receptor-mediated pathways, bridging systemic metabolism with local immune responses. In disease contexts, dysregulated immune dynamics drive osteoporosis via RANKL/IL-17 hyperactivity and promote leukemic evasion through microenvironmental immunosuppression. We further propose the “brain–gut–bone axis” as a systemic regulatory framework, wherein vagus nerve-mediated gut signaling enhances osteogenic pathways, while leptin and adipokine circuits link marrow adiposity to inflammatory bone loss. These insights redefine bone as a multidimensional immunometabolic organ, integrating neural, endocrine, and microbial inputs to maintain homeostasis. By elucidating the mechanisms of immune-driven bone pathologies, this work highlights therapeutic opportunities through biomaterial-mediated immunomodulation and microbiota-targeted interventions, paving the way for next-generation treatments in osteoimmune disorders. Full article

Inflammatory bowel disease (IBD) demonstrates chronic relapsing inflammation extending beyond adaptive immunity dysfunction. “Trained immunity”—the reprogramming of innate immune memory in myeloid cells and hematopoietic progenitors—maintains intestinal inflammation; however, the mechanism by which gut microbiome orchestration determines protective versus pathological outcomes remains unclear. Microbial metabolites demonstrate context-dependent dual effects along the gut–bone marrow axis. Short-chain fatty acids typically induce tolerogenic immune memory, whereas metabolites like succinate and polyamines exhibit dual roles: promoting inflammation in certain contexts while enhancing barrier integrity in others, influenced by cell-specific receptors and microenvironmental factors. Interventions include precision probiotics and postbiotics delivering specific metabolites, fecal microbiota transplantation addressing dysbiotic trained immunity, targeted metabolite supplementation, and pharmacologic reprogramming of pathological myeloid training states. Patient stratification based on microbiome composition and host genetics enhances therapeutic precision. Future research requires integration of non-coding RNAs regulating trained immunity, microbiome–immune–neuronal axis interactions, and host genetic variants modulating microbiome–immunity crosstalk. Priorities include developing companion diagnostics, establishing regulatory frameworks for microbiome therapeutics, and defining mechanistic switches for personalized interventions. Full article

Dietary patterns greatly affect periodontitis, a chronic inflammatory disease that compromises both dental and systemic health. According to the emerging evidence, periodontal risk is more strongly associated with the overall dietary quality, especially fiber density intake, than any one micronutrient. While the average intake in industrialized countries is only half of the recommended 30 g day⁻¹, high-fiber diets such as the Mediterranean diet, the Dietary Approaches to Stop Hypertension (DASH), and whole-food plant-based diets are consistently associated with a 20–40% lower periodontitis prevalence. Dietary fiber plays a central role in regulating immune responses, strengthening tissue barriers, improving metabolic homeostasis, and shaping a healthy microbiome through its microbial fermentation products: short-chain fatty acids (SCFAs). This makes it a biologically rational and clinical evidence-supported strategy for the prevention and management of periodontitis. Integrating high-fiber diet recommendations into routine periodontal care and public health policies could be a crucial step towards more comprehensive oral and systemic health management. This narrative review elaborates on the mechanistic, observational, and intervention data highlighting the role of dietary fiber, especially SCFAs, in periodontal health. Full article

The microbial community in a recirculating aquaculture system (RAS) is pivotal in fish health, contributing significantly to the productive performance during the growing-out phase. Classical and molecular methods using PCR for species-specific amplifications have traditionally been used for bacterial community surveillance. Unfortunately, these approaches mask the real bacterial diversity and abundance, population dynamics, and prevalence of pathogenic bacteria. In this study, we explored the use of Oxford Nanopore Technology to characterize the microbiota and functional metagenomics in a commercial freshwater RAS. Intestine samples from Atlantic salmon (Salmo salar (85 ± 5.7 g)) and water samples from the inlet/outlet water, settling tank, and biofilters were collected. The full-length 16S rRNA gene was sequenced to reconstruct the microbial community, and bioinformatic tools were applied to estimate the functional potential in the RAS and fish microbiota. The analysis showed that bacteria involved in denitrification processes were found in water samples, as well as metabolic pathways related to hydrogen sulfide metabolism. Observations suggested that fish classified as sick exhibited decreased microbial diversity compared with fish without clinical symptomatology (p < 0.05). Proteobacteria were predominant in ill fish, and pathogens of the genera Aeromonas, Aliivibrio, and Vibrio were detected in all intestinal samples. Notably, Aliivibrio wodanis was detected in fish showing abnormal clinical conditions. Healthy salmon showed higher contributions of pathways related to amino acid metabolism and short-chain fatty acid fermentation (p < 0.05), which may indicate more favorable fish conditions. These findings suggest the utility of nanopore sequencing methods in assessing the microbial community in RASs for salmon aquaculture. Full article

The aim of this study was to evaluate the effects of Flos lonicerae and Baikal skullcap extracts (PE) on laying performance, antioxidant capacity, immune function, follicular development, estrogen secretion, ovarian metabolomics, and cecal microbiota in aged laying hens. The total number of 70-week-old XinYang Black-Feathered laying hens was 240. These hens were randomly divided into two groups, with each group consisting of six replicates of 20 birds. Control (CON) group was fed a basal diet, whereas the PE group received the same basal diet supplemented with 500 mg/kg of PE. The duration of the experiment was 10 weeks. The findings indicated that the supplementation of PE improved laying performance, antioxidant capacity, and immune function. This was reflected by significant increases (p < 0.05) in laying rate, feed conversion ratio, antioxidant indicators (such as glutathione peroxidase, total antioxidant capacity, and catalase), and immunoglobulin levels. Additionally, there were notable decreases (p < 0.05) in the malondialdehyde levels and pro-inflammatory markers. Moreover, the PE group exhibited a greater number of large yellow and white follicles, as well as higher serum estrogen levels, compared to the CON group (p < 0.05). 16S rRNA sequencing revealed that PE supplementation altered the composition of the cecal microbiota by increasing Ruminococcus_torques_group, Butyricoccus and Christensenellaceae_R-7_group abundances and decreasing Bacteroides, Prevotellaceae_UCG-001 and Megamonas abundances (at genus level), which are primarily associated with short-chain fatty acid production. Ovarian metabolomic analysis showed that the major metabolites altered by PE supplementation were mainly involved in follicular development, estrogen biosynthesis, anti-inflammatory and antioxidant properties. Moreover, changes in both the cecal microbiota (at genus level) and ovarian metabolites were strongly correlated with laying performance, antioxidant status, and immune function. In conclusion, PE supplementation improved laying performance in aged hens by enhancing antioxidant, immune, and ovarian functions, promoting follicular development and estrogen secretion, and modulating the gut microbiota and ovarian metabolites. These findings will offer novel insights into the mechanisms that underlie egg production in the ovaries of aged poultry. Full article

Globally, Parkinson’s disease (PD) is the neurodegenerative condition with the most rapidly increasing prevalence, and a growing body of evidence associates its pathology with impairments in the gut–brain axis. Traditionally viewed as a disease marked by the loss of dopaminergic neurons, emerging evidence emphasizes that chronic neuroinflammation is a driver of neurodegeneration, with gut-originating inflammation playing a crucial role. Increased intestinal permeability, often called “leaky gut,” allows harmful substances, toxins, and misfolded α-synuclein into the systemic circulation, potentially exacerbating neuroinflammation and spreading α-synuclein pathology to the brain through the vagus nerve or compromised blood–brain barrier (BBB). This review synthesizes current insights into the relationship between gut health and PD, emphasizing the importance of gut permeability in disrupting intestinal barrier function. This paper highlights innovative therapeutic approaches, particularly personalized therapies involving gut microbiome engineering, as promising strategies for restoring gut integrity and improving neurological outcomes. Modulating specific gut bacteria to enhance the synthesis of certain metabolites, notably short-chain fatty acids (SCFAs), represents a promising strategy for reducing inflammatory responses and decelerating neurodegeneration in Parkinson’s disease. Full article

Objectives: Emerging evidence suggests that propolis possesses significant anti-obesity properties. While gut hormones and microbiota are known to play crucial roles in obesity development, the specific mechanisms through which propolis exerts its effects via the gut hormone axis remain poorly characterized. Methods: A high-fat diet (HFD) rat model was established to investigate the regulatory effects of propolis. After 10 weeks of intervention, blood serum, liver, colon tissues, and luminal contents were analyzed for metabolic parameters, gene expression of gut hormones and AMPK pathway markers, microbial community structure, and short-chain fatty acid production. Results: Propolis effectively mitigated HFD-induced metabolic disturbances, including excessive weight gain, adipose tissue accumulation, hyperlipidemia, and hepatic dysfunction. These improvements were associated with significant upregulation of the AMPK pathway. Importantly, propolis enhanced intestinal barrier integrity and differentially modulated gut hormone expression by increasing the mRNA levels of Cck, Gip, and Ghrl, and decreasing Lep and Gcg levels. 16S rRNA sequencing analysis revealed that propolis administration selectively enriched butyrate- and propionate-producing bacterial species. Correlation analysis further identified the Eubacterium brachy group as a pivotal microbial mediator in the propolis-modulated gut microbiota–gut hormone–liver AMPK axis. Conclusions: Our findings establish that propolis ameliorates obesity-related metabolic disorders by orchestrating crosstalk among gut microbiota, enteroendocrine hormones, and hepatic AMPK signaling. These results elucidate a novel mechanistic pathway in rodents; however, their direct translatability to humans requires further clinical investigation. This tripartite axis offers a mechanistic foundation for developing microbiota-targeted anti-obesity therapies. Full article