Altered Gut Microbiota in a Mouse Model of Alzheimer’s Disease

From Gut to Brain: The Role of Gut Dysbiosis, Bacterial Amyloids, and Metabolic Disease in Alzheimer's Disease

Gut microbial dysbiosis, or altered gut microbial communities, in Alzheimer's Disease suggests a pathogenic role for gut inflammation and microbial products in shaping a neuroinflammatory environment. Similarly, metabolic diseases, such as obesity and diabetes, are also associated with an increased risk of Alzheimer's Disease. As the metabolic landscape shifts during gut inflammation, and gut inflammation in turn impacts metabolic processes, we explore how these interconnected pathways may contribute to the progression of Alzheimer's Disease. Additionally, we discuss the role of bacterial amyloids produced by gut microbes, which may exacerbate amyloid aggregation in the brain and contribute to neurodegenerative processes. Furthermore, we highlight potential therapeutic strategies aimed at reducing gut inflammation, improving metabolic health, and decreasing amyloid content as a means to mitigate Alzheimer's Disease progression. These approaches, targeting the gut-brain-metabolic axis, could offer promising avenues for delaying or preventing cognitive decline in affected individuals.

Advances in molecular mechanisms and therapeutic strategies for central nervous system diseases based on gut microbiota imbalance

BACKGROUD

Central nervous system (CNS) diseases pose a serious threat to human health, but the regulatory mechanisms and therapeutic strategies of CNS diseases need to be further explored. It has been demonstrated that the gut microbiota (GM) is closely related to CNS disease. GM structure disorders, abnormal microbial metabolites, intestinal barrier destruction and elevated inflammation exist in patients with CNS diseases and promote the development of CNS diseases. More importantly, GM remodeling alleviates CNS pathology to some extent.

AIM OF REVIEW

Here, we have summarized the regulatory mechanism of the GM in CNS diseases and the potential treatment strategies for CNS repair based on GM regulation, aiming to provide safer and more effective strategies for CNS repair from the perspective of GM regulation.

KEY SCIENTIFIC CONCEPTS OF REVIEW

The abundance and composition of GM is closely associated with the CNS diseases. On the basis of in-depth analysis of GM changes in mice with CNS disease, as well as the changes in its metabolites, therapeutic strategies, such as probiotics, prebiotics, and FMT, may be used to regulate GM balance and affect its microbial metabolites, thereby promoting the recovery of CNS diseases.

Gut Microbiota Mediates Neuroinflammation in Alzheimer's Disease: Unraveling Key Factors and Mechanistic Insights

The gut microbiota, the complex community of microorganisms that inhabit the gastrointestinal tract, has emerged as a key player in the pathogenesis of neurodegenerative disorders, including Alzheimer's disease (AD). AD is characterized by progressive cognitive decline and neuronal loss, associated with the accumulation of amyloid-β plaques, neurofibrillary tangles, and neuroinflammation in the brain. Increasing evidence suggests that alterations in the composition and function of the gut microbiota, known as dysbiosis, may contribute to the development and progression of AD by modulating neuroinflammation, a chronic and maladaptive immune response in the central nervous system. This review aims to comprehensively analyze the current role of the gut microbiota in regulating neuroinflammation and glial cell function in AD. Its objective is to deepen our understanding of the pathogenesis of AD and to discuss the potential advantages and challenges of using gut microbiota modulation as a novel approach for the diagnosis, treatment, and prevention of AD.

Metabolic preferences of astrocytes: Functional metabolic mapping reveals butyrate outcompetes acetate

Disruptions to the gut-brain-axis have been linked to neurodegenerative disorders. Of these disruptions, reductions in the levels of short-chain fatty acids (SCFAs), like butyrate, have been observed in mouse models of Alzheimer's disease (AD). Butyrate supplementation in mice has shown promise in reducing neuroinflammation, amyloid-β accumulation, and enhancing memory. However, the underlying mechanisms remain unclear. To address this, we investigated the impact of butyrate on energy metabolism in mouse brain slices, primary cultures of astrocytes and neurons and in-vivo by dynamic isotope labelling with [U-13C]butyrate and [1,2-13C]acetate to map metabolism via mass spectrometry. Metabolic competition assays in cerebral cortical slices revealed no competition between butyrate and the ketone body, β-hydroxybutyrate, but competition with acetate. Astrocytes favoured butyrate metabolism compared to neurons, suggesting that the astrocytic compartment is the primary site of butyrate metabolism. In-vivo metabolism investigated in the 5xFAD mouse, an AD pathology model, showed no difference in 13C-labelling of TCA cycle metabolites between wild-type and 5xFAD brains, but butyrate metabolism remained elevated compared to acetate in both groups, indicating sustained uptake and metabolism in 5xFAD mice. Overall, these findings highlight the role of astrocytes in butyrate metabolism and the potential use of butyrate as an alternative brain fuel source.

Gut microbiota dysbiosis in Alzheimer's disease (AD): Insights from human clinical studies and the mouse AD models

Alzheimer's Disease (AD) is a debilitating neurocognitive disorder with an unclear underlying mechanism. Recent studies have implicated gut microbiota dysbiosis with the onset and progression of AD. The connection between gut microbiota and AD can significantly affect the prevention and treatment of AD patients. This systematic review summarizes primary outcomes of human and mouse AD models concerning gut microbiota alterations. A systematic literature search in February through March 2023 was conducted on PubMed, Embase, and Web of Science. We identified 711 as potential manuscripts of which 672 were excluded because of irrelevance to the identified search criteria. Primary outcomes include microbiota compositions of control and AD models in humans and mice. In total, 39 studies were included (19 mouse and 20 human studies), published between 2017 and 2023. We included studies involving well-established mice models of AD (5xFAD, 3xTg-AD, APP/PS1, Tg2576, and APPPS2) which harbor mutations and genes that drive the formation of Aß plaques. All human studies were included on those with AD or mild cognitive impairment. Among alterations in gut microbiota, most studies found a decreased abundance of the phyla Firmicutes and Bifidobacteria, a genus of the phylum Actinomycetota. An increased abundance of the phyla Bacteroidetes and Proteobacteria were identified in animal and human studies. Studies indicated that gut microbiota alter the pathogenesis of AD through its impact on neuroinflammation and permeability of the gastrointestinal tract. The ensuing increase in blood-brain barrier permeability may accelerate Aβ penetrance and formation of neuritic plaques that align with the amyloid hypothesis of AD pathogenesis. Further studies should assess the relationship between gut microbiota and AD progression and therapy preserving beneficial gut microbiota.

The Potential Role of Microbiota in Age-Related Cognitive Decline: A Narrative Review of the Underlying Molecular Mechanisms

As the world's population continues to age, social patterns are changing, making aging a notable public health challenge. With aging as the major risk factor for cognitive decline, the global prevalence of dementia is projected to triple in the next 25 years. In light of the growing body of evidence of the involvement of microbiota in health and pathology, its role in age-related cognitive decline should be explored. Therefore, the aim of this narrative review is to thoroughly analyze the ways in which microbiota might affect the aging process and age-related cognitive decline. Overall, aging is a complex phenomenon manifested at systemic, cellular and molecular levels. According to recent studies, gut microbiota composition may influence age-related changes through the gut-brain axis. One mechanism involves dysbiosis-related chronic systemic inflammation, leading to the blood-brain barrier disruption and subsequent neuroinflammatory processes. In addition to inflammaging, gut microbiota may induce oxidative stress, which is another key factor in brain aging. Finally, not only gut microbiota, but also microbiota colonizing the oral cavity may be associated with age-related neurodegenerative diseases.

Exploring the microbiota-gut-brain axis: impact on brain structure and function

The microbiota-gut-brain axis (MGBA) plays a significant role in the maintenance of brain structure and function. The MGBA serves as a conduit between the CNS and the ENS, facilitating communication between the emotional and cognitive centers of the brain via diverse pathways. In the initial stages of this review, we will examine the way how MGBA affects neurogenesis, neuronal dendritic morphology, axonal myelination, microglia structure, brain blood barrier (BBB) structure and permeability, and synaptic structure. Furthermore, we will review the potential mechanistic pathways of neuroplasticity through MGBA influence. The short-chain fatty acids (SCFAs) play a pivotal role in the MGBA, where they can modify the BBB. We will therefore discuss how SCFAs can influence microglia, neuronal, and astrocyte function, as well as their role in brain disorders such as Alzheimer's disease (AD), and Parkinson's disease (PD). Subsequently, we will examine the technical strategies employed to study MGBA interactions, including using germ-free (GF) animals, probiotics, fecal microbiota transplantation (FMT), and antibiotics-induced dysbiosis. Finally, we will examine how particular bacterial strains can affect brain structure and function. By gaining a deeper understanding of the MGBA, it may be possible to facilitate research into microbial-based pharmacological interventions and therapeutic strategies for neurological diseases.

Exploring the Relationship Between Sporadic Creutzfeldt-Jakob Disease and Gut Microbiota Through a Mendelian Randomization Study

Observational studies have shown gut microbiota changes in sporadic Creutzfeldt-Jakob disease patients, but the causal relationship remains unknown. We aimed to determine any causal links between gut microbiota and this prion disease. Using Mendelian randomization analysis, we examined the causal relationship between gut microbiota composition and sporadic Creutzfeldt-Jakob disease. Data on gut microbiota (N = 18,340) and disease cases (5208) were obtained. Various analysis methods were used, including inverse variance weighted, Mendelian randomization-Egger, weighted median, simple mode, and weighted mode. In addition, MR-PRESSO was used to evaluate horizontal pleiotropy and detect outliers. Pleiotropy and heterogeneity were assessed, and reverse analysis was conducted. Negative associations were found between sporadic Creutzfeldt-Jakob disease and family Defluviitaleaceae, family Ruminococcaceae, genus Butyricicoccus, genus Desulfovibrio, and genus Eubacterium nodatum. Genus Lachnospiraceae UCG010 showed a positive correlation. Reverse analysis indicated genetic associations between the disease and decreased levels of family Peptococcaceae, genus Faecalibacterium, and genus Phascolarctobacterium, as well as increased levels of genus Butyrivibrio. No pleiotropy, heterogeneity, outliers, or weak instrument bias were observed. This study revealed bidirectional causal effects between specific gut microbiota components and sporadic Creutzfeldt-Jakob disease. Certain components demonstrated inhibitory effects on disease pathogenesis, while others were positively associated with the disease. Modulating gut microbiota may provide new insights into prion disease therapies. Further research is needed to clarify mechanisms and explore treatments for sporadic Creutzfeldt-Jakob disease.

The complex relationship between gut microbiota and Alzheimer's disease: A systematic review

Alzheimer's disease (AD) is a progressive, degenerative disorder of the central nervous system. Despite extensive research conducted on this disorder, its precise pathogenesis remains unclear. In recent years, the microbiota-gut-brain axis has attracted considerable attention within the field of AD. The gut microbiota communicates bidirectionally with the central nervous system through the gut-brain axis, and alterations in its structure and function can influence the progression of AD. Consequently, regulating the gut microbiota to mitigate the progression of AD has emerged as a novel therapeutic approach. Currently, numerous studies concentrate on the intrinsic relationship between the microbiota-gut-brain axis and AD. In this paper, we summarize the multifaceted role of the gut microbiota in AD and present detailed therapeutic strategies targeting the gut microbiota, including the treatment of AD with Traditional Chinese Medicine (TCM), which has garnered increasing attention in recent years. Finally, we discuss potential therapeutic strategies for modulating the gut microbiota to alleviate the progression of AD, the current challenges in this area of research, and provide an outlook on future research directions in this field.

Aerobic exercise regulates gut microbiota profiles and metabolite in the early stage of Alzheimer's disease

Aerobic exercise (AE) has been shown to offer significant benefits for Alzheimer's disease (AD), potentially influencing the gut microbiota. However, the impact of changes in intestinal flora in early Alzheimer's disease induced by aerobic exercise on metabolic pathways and metabolites is not well understood. In this study, 3-month-old APP/PS1 and C57BL/6 mice were divided into two groups each: a control group (ADC for APP/PS1 and WTC for C57BL/6) and an aerobic exercise group (ADE for APP/PS1 and WTE for C57BL/6). The exercise groups underwent a 20-week aerobic training program on a motorized treadmill before the behavioral test (both the Morris water maze experiment (MWM) and the eight-arm maze test). Fecal samples were collected to analyze gut microbiota profiles via 16S rRNA gene sequencing. At the same time, the metabolic pathway analysis and the detection of metabolites were carried out. At the phylum level, the ADE group exhibited a significant reduced in the relative abundance of Bacteroidetes compared to the ADC group. At the genus level, both Ileibacterium and Faecalibaculum were found to be more abundant in the ADE group than in the ADC group. Additionally, PICRUSt analysis revealed that lipid metabolism and bile acid metabolism pathways were significantly enriched in the cecal microbiota of mice in the ADE group. The metabolites detected further confirmed the changes in the metabolic pathways mentioned above. Aerobic exercise may modify gut microbiota profiles and metabolites in APP/PS1 mice, thereby potentially playing a beneficial role in delaying cognitive impairment associated with early-stage Alzheimer's disease.

Protection of Alzheimer's disease progression by a human-origin probiotics cocktail

Microbiome abnormalities (dysbiosis) significantly contribute to the progression of Alzheimer's disease (AD). However, the therapeutic efficacy of microbiome modulators in protecting against these ailments remains poorly studied. Herein, we tested a cocktail of unique probiotics, including 5 Lactobacillus and 5 Enterococcus strains isolated from infant gut with proven microbiome modulating capabilities. We aimed to determine the probiotics cocktail's efficacy in ameliorating AD pathology in a humanized AD mouse model of APP/PS1 strains. Remarkably, feeding mice with 1 × 1011 CFU per day in drinking water for 16 weeks significantly reduced cognitive decline (measured by the Morris Water Maze test) and AD pathology markers, such as Aβ aggregation, microglia activation, neuroinflammation, and preserved blood-brain barrier (BBB) tight junctions. The beneficial effects were linked to a reduced inflammatory microbiome, leading to decreased gut permeability and inflammation in both systemic circulation and the brain. Although both male and female mice showed overall improvements in cognition and biological markers, females did not exhibit improvements in specific markers related to inflammation and barrier permeability, suggesting that the underlying mechanisms may differ depending on sex. In conclusion, our results suggest that this unique probiotics cocktail could serve as a prophylactic agent to reduce the progression of cognitive decline and AD pathology. This is achieved by beneficially modulating the microbiome, improving intestinal tight junction proteins, reducing permeability in both gut and BBB, and decreasing inflammation in the gut, blood circulation, and brain, ultimately mitigating AD pathology and cognitive decline.

Shattering the Amyloid Illusion: The Microbial Enigma of Alzheimer's Disease Pathogenesis-From Gut Microbiota and Viruses to Brain Biofilms

For decades, Alzheimer's Disease (AD) research has focused on the amyloid cascade hypothesis, which identifies amyloid-beta (Aβ) as the primary driver of the disease. However, the consistent failure of Aβ-targeted therapies to demonstrate efficacy, coupled with significant safety concerns, underscores the need to rethink our approach to AD treatment. Emerging evidence points to microbial infections as environmental factors in AD pathoetiology. Although a definitive causal link remains unestablished, the collective evidence is compelling. This review explores unconventional perspectives and emerging paradigms regarding microbial involvement in AD pathogenesis, emphasizing the gut-brain axis, brain biofilms, the oral microbiome, and viral infections. Transgenic mouse models show that gut microbiota dysregulation precedes brain Aβ accumulation, emphasizing gut-brain signaling pathways. Viral infections like Herpes Simplex Virus Type 1 (HSV-1) and Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) may lead to AD by modulating host processes like the immune system. Aβ peptide's antimicrobial function as a response to microbial infection might inadvertently promote AD. We discuss potential microbiome-based therapies as promising strategies for managing and potentially preventing AD progression. Fecal microbiota transplantation (FMT) restores gut microbial balance, reduces Aβ accumulation, and improves cognition in preclinical models. Probiotics and prebiotics reduce neuroinflammation and Aβ plaques, while antiviral therapies targeting HSV-1 and vaccines like the shingles vaccine show potential to mitigate AD pathology. Developing effective treatments requires standardized methods to identify and measure microbial infections in AD patients, enabling personalized therapies that address individual microbial contributions to AD pathogenesis. Further research is needed to clarify the interactions between microbes and Aβ, explore bacterial and viral interplay, and understand their broader effects on host processes to translate these insights into clinical interventions.

Fecal Microbiota Transplantation from Methionine-Restricted Diet Mouse Donors Improves Alzheimer's Learning and Memory Abilities Through Short-Chain Fatty Acids

Alzheimer's disease (AD) is marked by impaired cognitive functions, particularly in learning and memory, owing to complex and diverse mechanisms. Methionine restriction (MR) has been found to exert a mitigating effect on brain oxidative stress to improve AD. However, the bidirectional crosstalk between the gut and brain through which MR enhances learning and memory in AD, as well as the effects of fecal microbiota transplantation (FMT) from MR mice on AD mice, remains underexplored. In this study, APP/PS1 double transgenic AD mice were used and an FMT experiment was conducted. 16S rRNA gene sequencing, targeted metabolomics, and microbial metabolite short-chain fatty acids (SCFAs) of feces samples were analyzed. The results showed that MR reversed the reduction in SCFAs induced by AD, and further activated the free fatty acid receptors, FFAR2 and FFAR3, as well as the transport protein MCT1, thereby signaling to the brain to mitigate inflammation and enhance the learning and memory capabilities. Furthermore, the FMT experiment from methionine-restricted diet mouse donors showed that mice receiving FMT ameliorated Alzheimer's learning and memory ability through SCFAs. This study offers novel non-pharmaceutical intervention strategies for AD prevention.

Ginseng as a therapeutic target to alleviate gut and brain diseases via microbiome regulation

The human gut, which contains a diverse microbiome, plays an important role in maintaining physiological balance and preserving the immune system. The complex interplay between the central nervous system (CNS) and the gut microbiome has gained significant attention due to its profound implications for overall health, particularly for gut and brain disorders. There is emerging evidence that the gut-brain axis (GBA) represents a bidirectional communication system between the CNS and the gastrointestinal tract and plays a pivotal role in regulating many aspects of human health. Ginseng has shown potential to ameliorate conditions associated with dysbiosis, such as gut and CNS disorders by restoring microbial balance and enhancing gut barrier function. This comprehensive review provides valuable insights into the potential of ginseng as a herbal modulator of GBA as a therapeutic intervention for preventing and treating gut and neurological diseases via microbiota regulation to ultimately enhance overall health. Furthermore, we emphasize the therapeutic benefits of ginseng, its ability to enhance beneficial probiotics, such as Firmicutes, Bacteroides, Lactobacillus, Bifidobacterium, and Akkermansia while reducing pathogenic bacteria prevalence, such as Helicobacter, Clostridium, and Proteobacteria. Although the connection between ginseng regulation of microbial communities in response to the gut and neuropsychiatric disorders is lacking, additional investigations are warranted to elucidate the underlying mechanisms, optimize dosages, and explore the clinical relevance of ginseng in promoting GBA balance and ultimately overall health.

The Gut Microbiota-Brain Axis: A New Frontier in Alzheimer's Disease Pathology

Dr. Aloysius Alzheimer, a German neuropathologist and psychiatrist, recognized the primary instance of Alzheimer's disease (AD) for a millennium, and this ailment, along with its related dementias, remains a severe overall community issue related to health. Nearly fifty million individuals worldwide suffer from dementia, with Alzheimer's illness contributing to between 60 and 70% of the instances, estimated through the World Health Organization. In addition, 82 million individuals are anticipated to be affected by the global dementia epidemic by 2030 and 152 million by 2050. Furthermore, age, environmental circumstances, and inherited variables all increase the likelihood of acquiring neurodegenerative illnesses. Most recent pharmacological treatments are found in original hypotheses of disease, which include cholinergic (drugs that show affective cholinergic system availability) as well as amyloid-accumulation (a single drug is an antagonist receptor of Nmethyl D-aspartate). In 2020, the FDA provided approval on anti-amyloid drugs. According to mounting scientific data, this gut microbiota affects healthy physiological homeostasis and has a role in the etiology of conditions that range between obesity and neurodegenerative disorders like Alzheimer's. The microbiota-gut-brain axis might facilitate interconnection among gut microbes as well as the central nervous system (CNS). Interaction among the microbiota-gut system as well as the brain occurs through the "two-way" microbiota-gut-brain axis. Along this axis, the stomach as well as the brain develop physiologically and take on their final forms. This contact is constant and is mediated by numerous microbiota-derived products. The gut microbiota, for instance, can act as non-genetic markers to set a threshold for maintaining homeostasis or getting ill. The scientific community has conducted research and found that bowel dysbiosis and gastrointestinal tract dysregulation frequently occur in Alzheimer's disease (AD) patients. In this review, the effects of the microbiota- gut-brain axis on AD pathogenesis will be discussed.

Dietary interventions in mitigating the impact of environmental pollutants on Alzheimer's disease - A review

Numerous studies linking environmental pollutants to oxidative stress, inflammation, and neurotoxicity have assigned pollutants to several neurodegenerative disorders, including Alzheimer's disease (AD). Heavy metals, pesticides, air pollutants, and endocrine disruptor chemicals have been shown to play important roles in AD development, with some traditional functions in amyloid-β formation, tau kinase action, and neuronal degeneration. However, pharmacological management and supplementation have resulted in limited improvement. This raises the interesting possibility that activities usually considered preventive, including diet, exercise, or mental activity, might be more similar to treatment or therapy for AD. This review focuses on the effects of diet on the effects of environmental pollutants on AD. One of the primary issues addressed in this review is a group of specific diets, including the Mediterranean diet (MeDi), Dietary Approaches to Stop Hypertension (DASH), and Mediterranean-DASH intervention for Neurodegenerative Delay (MIND), which prevent exposure to these toxins. Such diets have been proven to decrease oxidative stress and inflammation, which are unfavorable for neuronal growth. Furthermore, they contribute to positive changes in the composition of the human gut microbiota and thus encourage interactions in the Gut-Brain Axis, reducing inflammation caused by pollutants. This review emphasizes a multi-professional approach with reference to nutritional activities that would lower the neurotoxic load in populations with a high level of exposure to pollutants. Future studies focusing on diet and environment association plans may help identify preventive measures aimed at enhancing current disease deceleration.

Ameliorative effects of Akkermansia muciniphila on anxiety-like behavior and cognitive deficits in a rat model of Alzheimer's disease

Alzheimer's Disease (AD) is the primary neurodegenerative disorder in the elderly, lacking a definitive treatment. The gut microbiota influences the gut-brain axis by aiding in hypothalamic-pituitary-adrenal (HPA) axis development and neuromodulator production. Research links AD and gut microbiota, suggesting gut microbiota regulation could be a therapeutic approach for AD. This study explores Akkermansia muciniphila's impact on preventing AD. This research investigates the effect of A. muciniphila consumption (1 × 109 CFU) on tau protein-induced AD rats compared to a control group. Rats were divided into four groups: sham, sham + Akk, AD (tau-induced rats), and AD + Akk (tau-induced rats treated with A. muciniphila). A. muciniphila gavage lasted five weeks. Rats underwent qRT-PCR analysis to assess mRNA expression of pro-inflammatory factors (TNF-α, IL-6, IL-1β, IFN-γ) in the hippocampus. Behavioral tests included Morris Water Maze (MWM), Passive Avoidance Memory Test (Shuttle box), Elevated Plus Maze (EPM), and marble burying. After five weeks of A. muciniphila treatment, anxiety-like behavior significantly decreased. The AD group receiving A. muciniphila showed improved spatial and recognition memory compared to the AD group. Pro-inflammatory cytokine levels (TNF-α, IL-1β, IL-6, IFN-γ) decreased. A. muciniphila effectively reduces cognitive impairments and anxiety-related behavior, showing promise as an AD therapeutic by influencing the gut-brain axis.

A Review of the Consequences of Gut Microbiota in Neurodegenerative Disorders and Aging

Age-associated alterations in the brain lead to cognitive deterioration and neurodegenerative disorders (NDDs). This review with a particular focus on Alzheimer's disease (AD), emphasizes the burgeoning significance of the gut microbiota (GMB) in neuroinflammation and its impact on the gut-brain axis (GBA), a communication conduit between the gut and the central nervous system (CNS). Changes in the gut microbiome, including diminished microbial diversity and the prevalence of pro-inflammatory bacteria, are associated with AD pathogenesis. Promising therapies, such as fecal microbiota transplantation (FMT), probiotics, and prebiotics, may restore gut health and enhance cognitive performance. Clinical data remain insufficient, necessitating further research to elucidate causes, enhance therapy, and consider individual variances. This integrative approach may yield innovative therapies aimed at the GMB to improve cognitive function and brain health in older people.

Gut microbiome and Alzheimer's disease: What we know and what remains to be explored

With advancement in human microbiome research, an increasing number of scientific evidences have endorsed the key role of gut microbiota in the pathogenesis of Alzheimer disease. Microbiome dysbiosis, characterized by altered diversity and composition, as well as rise of pathobionts influence not only various gut disorder but also central nervous system disorders such as AD. On the basis of accumulated evidences of past few years now it is quite clear that the gut microbiota can control the functions of the central nervous system (CNS) through the gut-brain axis, which provides a new prospective into the interactions between the gut and brain. The main focus of this review is on the molecular mechanism of the crosstalk between the gut microbiota and the brain through the gut-brain axis, and on the onset and development of neurological disorders triggered by the dysbiosis of gut microbiota. Due to microbiota dysbiosis the permeability of the gut and blood brain barrier is increased which may mediate or affect AD. Along with this, bacterial population of the gut microbiota can secrete amyloid proteins and lipopolysaccharides in a large quantity which may create a disturbance in the signaling pathways and the formation of proinflammatory cytokines associated with the pathogenesis of AD. These topics are followed by a critical analysis of potential intervention strategies targeting gut microbiota dysbiosis, including the use of probiotics, prebiotics, metabolites, diets and fecal microbiota transplantation. The main purpose of this review includes the summarization and discussion on the recent finding that may explain the role of the gut microbiota in the development of AD. Understanding of these fundamental mechanisms may provide a new insight into the novel therapeutic strategies for AD.

Cross-talk between adipose tissue and microbiota-gut-brain-axis in brain development and neurological disorder

The gut microbiota is an important factor responsible for the physiological processes as well as pathogenesis of host. The communication between central nervous system (CNS) and microbiota occurs by different pathways i.e., chemical, neural, immune, and endocrine. Alteration in gut microbiota i.e., gut dysbiosis causes alteration in the bidirectional communication between CNS and gut microbiota and linked to the pathogenesis of neurological and neurodevelopmental disorder. Therefore, now-a-days microbiota-gut-brain-axis (MGBA) has emerged as therapeutic target for the treatment of metabolic disorder. But, experimental data available on MGBA from basic research has limited application in clinical study. In present study we first summarized molecular mechanism of microbiota interaction with brain physiology and pathogenesis via collecting data from different sources i.e., PubMed, Scopus, Web of Science. Furthermore, evidence shows that adipose tissue (AT) is active during metabolic activities and may also interact with MGBA. Hence, in present study we have focused on the relationship among MGBA, brown adipose tissue, and white adipose tissue. Along with this, we have also studied functional specificity of AT, and understanding heterogeneity among MGBA and different types of AT. Therefore, molecular interaction among them may provide therapeutic target for the treatment of neurological disorder.

Blood-derived factors to brain communication in brain diseases

Brain diseases, mainly including acute brain injuries, neurodegenerative diseases, and mental disorders, have posed a significant threat to human health worldwide. Due to the limited regenerative capability and the existence of the blood-brain barrier, the brain was previously thought to be separated from the rest of the body. Currently, various cross-talks between the central nervous system and peripheral organs have been widely described, including the brain-gut axis, the brain-liver axis, the brain-skeletal muscle axis, and the brain-bone axis. Moreover, several lines of evidence indicate that leveraging systemic biology intervention approaches, including but not limited to lifestyle interventions, exercise, diet, blood administration, and peripheral immune responses, have demonstrated a significant influence on the progress and prognosis of brain diseases. The advancement of innovative proteomic and transcriptomic technologies has enriched our understanding of the nuanced interplay between peripheral organs and brain diseases. An array of novel or previously underappreciated blood-derived factors have been identified to play pivotal roles in mediating these communications. In this review, we provide a comprehensive summary of blood-to-brain communication following brain diseases. Special attention is given to the instrumental role of blood-derived signals, positing them as significant contributors to the complex process of brain diseases. The insights presented here aim to bridge the current knowledge gaps and inspire novel therapeutic strategies for brain diseases.

The human gut microbiome in health and disease: time for a new chapter?

The gut microbiome, composed of the colonic microbiota and their host environment, is important for many aspects of human health. A gut microbiome imbalance (gut dysbiosis) is associated with major causes of human morbidity and mortality. Despite the central part our gut microbiome plays in health and disease, mechanisms that maintain homeostasis and properties that demarcate dysbiosis remain largely undefined. Here we discuss that sorting taxa into meaningful ecological units reveals that the availability of respiratory electron acceptors, such as oxygen, in the host environment has a dominant influence on gut microbiome health. During homeostasis, host functions that limit the diffusion of oxygen into the colonic lumen shelter a microbial community dominated by primary fermenters from atmospheric oxygen. In turn, primary fermenters break down unabsorbed nutrients into fermentation products that support host nutrition. This symbiotic relationship is disrupted when host functions that limit the luminal availability of host-derived electron acceptors become weakened. The resulting changes in the host environment drive alterations in the microbiota composition, which feature an elevated abundance of facultatively anaerobic microbes. Thus, the part of the gut microbiome that becomes imbalanced during dysbiosis is the host environment, whereas changes in the microbiota composition are secondary to this underlying cause. This shift in our understanding of dysbiosis provides a novel starting point for therapeutic strategies to restore microbiome health. Such strategies can either target the microbes through metabolism-based editing or strengthen the host functions that control their environment.

Propionate Decreases Microglial Activation but Impairs Phagocytic Capacity in Response to Aggregated Fibrillar Amyloid Beta Protein

Microglia, the innate immune cell of the brain, are a principal player in Alzheimer's disease (AD) pathogenesis. Their surveillance of the brain leads to interaction with the protein aggregates that drive AD pathogenesis, most notably Amyloid Beta (Aβ). Microglia attempt to clear and degrade Aβ using phagocytic machinery, spurring damaging neuroinflammation in the process. Thus, modulation of the microglial response to Aβ is crucial in mitigating AD pathophysiology. SCFAs, microbial byproducts of dietary fiber fermentation, are blood-brain barrier permeable molecules that have recently been shown to modulate microglial function. It is unclear whether propionate, one representative SCFA, has beneficial or detrimental effects on microglia in AD. Thus, we investigated its impact on microglial Aβ response in vitro. Using a multiomics approach, we characterized the transcriptomic, metabolomic, and lipidomic responses of immortalized murine microglia following 1 h of Aβ stimulation, as well as characterizing Aβ phagocytosis and secretion of reactive nitrogen species. Propionate blunted the early inflammatory response driven by Aβ, downregulating the expression of many Aβ-stimulated immune genes, including those regulating inflammation, the immune complement system, and chemotaxis. Further, it reduced the expression of Apoe and inflammation-promoting Aβ-binding scavenger receptors such as Cd36 and Msr1 in favor of inflammation-dampening Lpl, although this led to impaired phagocytosis. Finally, propionate shifted microglial metabolism, altering phospholipid composition and diverting arginine metabolism, resulting in decreased nitric oxide production. Altogether, our data demonstrate a modulatory role of propionate on microglia that may dampen immune activation in response to Aβ, although at the expense of phagocytic capacity.

Microglia and gut microbiota: A double-edged sword in Alzheimer's disease

The strong association between gut microbiota (GM) and brain functions such as mood, behaviour, and cognition has been well documented. Gut-brain axis is a unique bidirectional communication system between the gut and brain, in which gut microbes play essential role in maintaining various molecular and cellular processes. GM interacts with the brain through various pathways and processes including, metabolites, vagus nerve, HPA axis, endocrine system, and immune system to maintain brain homeostasis. GM dysbiosis, or an imbalance in GM, is associated with several neurological disorders, including anxiety, depression, and Alzheimer's disease (AD). Conversely, AD is sustained by microglia-mediated neuroinflammation and neurodegeneration. Further, GM and their products also affect microglia-mediated neuroinflammation and neurodegeneration. Despite the evidence connecting GM dysbiosis and AD progression, the involvement of GM in modulating microglia-mediated neuroinflammation in AD remains elusive. Importantly, deciphering the mechanism/s by which GM regulates microglia-dependent neuroinflammation may be helpful in devising potential therapeutic strategies to mitigate AD. Herein, we review the current evidence regarding the involvement of GM dysbiosis in microglia activation and neuroinflammation in AD. We also discuss the possible mechanisms through which GM influences the functioning of microglia and its implications for therapeutic intervention. Further, we explore the potential of microbiota-targeted interventions, such as prebiotics, probiotics, faecal microbiota transplantation, etc., as a novel therapeutic strategy to mitigate neuroinflammation and AD progression. By understanding and exploring the gut-brain axis, we aspire to revolutionize the treatment of neurodegenerative disorders, many of which share a common theme of microglia-mediated neuroinflammation and neurodegeneration.

Characterization of gut microbiota dynamics in an Alzheimer's disease mouse model through clade-specific marker-based analysis of shotgun metagenomic data

Alzheimer's disease (AD) is a complex neurodegenerative disorder significantly impairing cognitive faculties, memory, and physical abilities. To characterize the modulation of the gut microbiota in an in vivo AD model, we performed shotgun metagenomics sequencing on 3xTgAD mice at key time points (i.e., 2, 6, and 12 months) of AD progression. Fecal samples from both 3xTgAD and wild-type mice were collected, DNA extracted, and sequenced. Quantitative taxon abundance assessment using MetaPhlAn 4 ensured precise microbial community representation. The analysis focused on species-level genome bins (SGBs) including both known and unknown SGBs (kSGBs and uSGBs, respectively) and also comprised higher taxonomic categories such as family-level genome bins (FGBs), class-level genome bins (CGBs), and order-level genome bins (OGBs). Our bioinformatic results pinpointed the presence of extensive gut microbial diversity in AD mice and showed that the largest proportion of AD- and aging-associated microbiome changes in 3xTgAD mice concern SGBs that belong to the Bacteroidota and Firmicutes phyla, along with a large set of uncharacterized SGBs. Our findings emphasize the need for further advanced bioinformatic studies for accurate classification and functional analysis of these elusive microbial species in relation to their potential bridging role in the gut-brain axis and AD pathogenesis.

Intestinal endogenous metabolites affect neuroinflammation in 5×FAD mice by mediating "gut-brain" axis and the intervention with Chinese Medicine

BACKGROUND

Emerging evidence suggested the association between gut dysbiosis and Alzheimer's disease (AD) progression. However, it remained unclear how the gut microbiome and neuroinflammation in the brain mutually interact or how these interactions affect brain functioning and cognition. Here we hypothesized that "gut-brain" axis mediated by microbial derived metabolites was expected to novel breakthroughs in the fields of AD research and development.

METHODS

Multiple technologies, such as immunofluorescence, 16s rDNA sequencing, mass spectrometry-based metabolomics (LC-QQQ-MS and GC-MS), were used to reveal potential link between gut microbiota and the metabolism and cognition of the host.

RESULTS

Microbial depletion induced by the antibiotics mix (ABX) verified that "gut-brain" can transmit information bidirectionally. Short-chain fatty acid-producing (SCFAs-producing) bacteria and amino acid-producing bacteria fluctuated greatly in 5×FAD mice, especially the reduction sharply of the Bifidobacteriaceae and the increase of the Lachnospiraceae family. Concentrations of several Tryptophan-kynurenine intermediates, lactic acid, CD4+ cell, and CD8+ cells were higher in serum of 5×FAD mice, whilst TCA cycle intermediates and Th1/Th2 were lower. In addition, the levels of iso-butyric acid (IBA) in feces, serum, and brain of 5×FAD mice were increased compared with WT-M mice, especially in serum. And IBA in the brain was positively correlated with Aβ and proinflammatory factors.

CONCLUSION

Together, our finding highlighted that the alternation in gut microbiota affected the effective communication between the "gut-brain" axis in 5×FAD mice by regulating the immune system, carbohydrate, and energy metabolism.

Disrupted gut harmony in attention-deficit/hyperactivity disorder: Dysbiosis and decreased short-chain fatty acids

Background

Attention-Deficit Hyperactivity Disorder (ADHD) is a prevalent neurodevelopmental disorder with complex genetic and environmental underpinnings. Emerging evidence suggests a significant role of gut microbiota in ADHD pathophysiology. This study investigates variations in gut microbiota composition and Short-Chain Fatty Acid (SCFA) profiles between children and adolescents with ADHD and healthy controls.

Methods

The study included 42 ADHD patients and 31 healthy controls, aged 6-18 years. Fecal samples were analyzed for microbial composition using 16S rRNA gene sequencing and for SCFA profiles through gas chromatography-mass spectrometry (GC-MS). The study assessed both α and β diversity of gut microbiota and quantified various SCFAs to compare between the groups.

Results

ADHD subjects demonstrated significantly reduced gut microbiota diversity, as indicated by lower α-diversity indices (Shannon index, Observed species, Faith PD index) and a trend towards significance in β-diversity (Weighted UniFrac). Notably, the ADHD group exhibited significantly lower levels of key SCFAs, including acetic, propionic, isobutyric, isovaleric, and valeric acids, highlighting a distinct microbial and metabolic profile in these individuals.

Conclusion

This study uncovers significant alterations in gut microbiota and SCFA profiles in children with ADHD, compared to healthy controls. The observed changes in SCFAs, known for their associations with other behavioral and neurologic pathologies, and for their role in neural signaling. These findings offer a metabolite fingerprint that could potentially lead to novel diagnostic and treatment approaches for ADHD, emphasizing the importance of gut microbiota in the disorder's pathogenesis and management.

The Gut Microbiota Modulates Neuroinflammation in Alzheimer's Disease: Elucidating Crucial Factors and Mechanistic Underpinnings

BACKGROUND AND PURPOSE

Alzheimer's disease (AD) is characterized by progressive cognitive decline and neuronal loss, commonly linked to amyloid-β plaques, neurofibrillary tangles, and neuroinflammation. Recent research highlights the gut microbiota as a key player in modulating neuroinflammation, a critical pathological feature of AD. Understanding the role of the gut microbiota in this process is essential for uncovering new therapeutic avenues and gaining deeper insights into AD pathogenesis.

METHODS

This review provides a comprehensive analysis of how gut microbiota influences neuroinflammation and glial cell function in AD. A systematic literature search was conducted, covering studies from 2014 to 2024, including reviews, clinical trials, and animal studies. Keywords such as "gut microbiota," "Alzheimer's disease," "neuroinflammation," and "blood-brain barrier" were used.

RESULTS

Dysbiosis, or the imbalance in gut microbiota composition, has been implicated in the modulation of key AD-related mechanisms, including neuroinflammation, blood-brain barrier integrity, and neurotransmitter regulation. These disruptions may accelerate the onset and progression of AD. Additionally, therapeutic strategies targeting gut microbiota, such as probiotics, prebiotics, and fecal microbiota transplantation, show promise in modulating AD pathology.

CONCLUSIONS

The gut microbiota is a pivotal factor in AD pathogenesis, influencing neuroinflammation and disease progression. Understanding the role of gut microbiota in AD opens avenues for innovative diagnostic, preventive, and therapeutic strategies.

Explore the mechanisms of triterpenoids from Ganoderma lucidum in the protection against Alzheimer's disease via microbiota-gut-brain axis with the aid of network pharmacology

Ganoderma lucidum (Curtis) P. Karst.(G. lucidum) is a kind of fungi, which also a traditional Chinese medicine used for "wisdom growth" in China. Triterpenoids from G. lucidum (GLTs) are one of the main active ingredients. Based on the strategy of early intervention on Alzheimer's disease (AD) and the inextricable association between disordered gut microbiota and metabolites with AD, this study aimed to explore the mechanisms of GLTs in the protection against AD via microbiota-gut-brain axis with the aid of network pharmacology. In this study, LC-MS/MS was used to identify the main active ingredients of GLTs. Network pharmacology was used to predict the potential target and validated with Caco-2 cell model. D-galactose was used to induce the slow-onset AD on rats. Metabolomics methods basing on GC-MS combined with 16S rRNA sequencing technology was used to carry out microbiota-gut-metabolomics analysis in order to reveal the potential mechanisms of GLTs in the protection of AD. As results, GLTs showed a protection against AD effect on rats by intervening administration. The mechanisms were inextricably linked to GLTs interference with the balance of gut microbiota and metabolites. The main fecal metabolites involved were short-chain fatty acids and aromatic amino acid metabolites.

Gut microbiome-derived metabolites in Alzheimer's disease: Regulation of immunity and potential for therapeutics

Alzheimer's disease (AD) is the most common neurodegenerative disorder and cause of dementia. Despite the prevalence of AD, there is a lack of effective disease modifying therapies. Recent evidence indicates that the gut microbiome (GMB) may play a role in AD through its regulation of innate and adaptive immunity. Gut microbes regulate physiology through their production of metabolites and byproducts. Microbial metabolites may be beneficial or detrimental to the pathogenesis and progression of inflammatory diseases. A better understanding of the role GMB-derived metabolites play in AD may lead to the development of therapeutic strategies for AD. In this review, we summarize the function of bioactive GMB-derived metabolites and byproducts and their roles in AD models. We also call for more focus on this area in the gut-brain axis field in order to create effective therapies for AD.

The Microbiota-Gut-Brain Axis and Neurological Disorders: A Comprehensive Review

Microbes have inhabited the earth for hundreds of millions of years longer than humans. The microbiota-gut-brain axis (MGBA) represents a bidirectional communication pathway. These communications occur between the central nervous system (CNS), the enteric nervous system (ENS), and the emotional and cognitive centres of the brain. The field of research on the gut-brain axis has grown significantly during the past two decades. Signalling occurs between the gut microbiota and the brain through the neural, endocrine, immune, and humoral pathways. A substantial body of evidence indicates that the MGBA plays a pivotal role in various neurological diseases. These include Alzheimer's disease (AD), autism spectrum disorder (ASD), Rett syndrome, attention deficit hyperactivity disorder (ADHD), non-Alzheimer's neurodegeneration and dementias, fronto-temporal lobe dementia (FTLD), Wilson-Konovalov disease (WD), multisystem atrophy (MSA), Huntington's chorea (HC), Parkinson's disease (PD), multiple sclerosis (MS), amyotrophic lateral sclerosis (ALS), temporal lobe epilepsy (TLE), depression, and schizophrenia (SCZ). Furthermore, the bidirectional correlation between therapeutics and the gut-brain axis will be discussed. Conversely, the mood of delivery, exercise, psychotropic agents, stress, and neurologic drugs can influence the MGBA. By understanding the MGBA, it may be possible to facilitate research into microbial-based interventions and therapeutic strategies for neurological diseases.

Cutting-Edge iPSC-Based Approaches in Studying Host-Microbe Interactions in Neuropsychiatric Disorders

Gut microbiota (GM), together with its metabolites (such as SCFA, tryptophan, dopamine, GABA, etc.), plays an important role in the functioning of the central nervous system. Various neurological and psychiatric disorders are associated with changes in the composition of GM and their metabolites, which puts them in the foreground as a potential adjuvant therapy. However, the molecular mechanisms behind this relationship are not clear enough. Therefore, before considering beneficial microbes and/or their metabolites as potential therapeutics for brain disorders, the mechanisms underlying microbiota-host interactions must be identified and characterized in detail. In this review, we summarize the current knowledge of GM alterations observed in prevalent neurological and psychiatric disorders, multiple sclerosis, major depressive disorder, Alzheimer's disease, and autism spectrum disorders, together with experimental evidence of their potential to improve patients' quality of life. We further discuss the main obstacles in the study of GM-host interactions and describe the state-of-the-art solution and trends in this field, namely "culturomics" which enables the culture and identification of novel bacteria that inhabit the human gut, and models of the gut and blood-brain barrier as well as the gut-brain axis based on induced pluripotent stem cells (iPSCs) and iPSC derivatives, thus pursuing a personalized medicine agenda for neuropsychiatric disorders.

Effects of saponins Rb1 and Re in American ginseng intervention on intestinal microbiota of aging model

Aging brings about physiological dysfunction, disease, and eventual mortality. An increasing number of studies indicate that aging can easily lead to dysbiosis of the gut microbiota, which can further affect digestion, nerves, cognition, emotions, and more. Therefore, gut bacteria play an important role in regulating the physical functions of aging populations. While saponins, the primary components of American ginseng, are frequently utilized for treating common ailments in the elderly due to their potent antioxidant properties, there is a scarcity of comprehensive studies on aging organisms. This study focused on 18 month old aging mice and investigated the effects of single intervention and combined intervention of Rb1 and Re, the main components of Panax quinquefolium saponins, on the gut microbiota of aging mice. High throughput 16s RNA gene sequencing analysis was performed on the gut contents of the tested mice, and the results showed that Rb1 and Re had a significant impact on the gut microbiota. Rb1, Re, and Rb1 + Re can effectively enhance the diversity of gut microbiota, especially in the combined Rb1 + Re group, which can recover to the level of young mice. Re can promote the abundance of probiotics such as Lactobacillus, Lactobacillaceae, and Lactobacillus, and inhibit the abundance of harmful bacteria such as Enterobacteriaceae. This indicates that the intervention of Rb1, Re, and Rb1 + Re can maintain the homeostasis of gut microbiota, and the combined application of Rb1 + Re has a better effect. The relationship between aging, brain gut axis, and gut microbiota is very close. Saponins can improve the gut microbiota of aging individuals by maintaining the balance of gut microbiota and the normal function of the brain gut axis, enabling the body to achieve a gut microbiota homeostasis closer to that of young healthy mice.

Psychobiotic Properties of Lactiplantibacillus plantarum in Neurodegenerative Diseases

Neurodegenerative disorders are the main cause of cognitive and physical disabilities, affect millions of people worldwide, and their incidence is on the rise. Emerging evidence pinpoints a disturbance of the communication of the gut-brain axis, and in particular to gut microbial dysbiosis, as one of the contributors to the pathogenesis of these diseases. In fact, dysbiosis has been associated with neuro-inflammatory processes, hyperactivation of the neuronal immune system, impaired cognitive functions, aging, depression, sleeping disorders, and anxiety. With the rapid advance in metagenomics, metabolomics, and big data analysis, together with a multidisciplinary approach, a new horizon has just emerged in the fields of translational neurodegenerative disease. In fact, recent studies focusing on taxonomic profiling and leaky gut in the pathogenesis of neurodegenerative disorders are not only shedding light on an overlooked field but are also creating opportunities for biomarker discovery and development of new therapeutic and adjuvant strategies to treat these disorders. Lactiplantibacillus plantarum (LBP) strains are emerging as promising psychobiotics for the treatment of these diseases. In fact, LBP strains are able to promote eubiosis, increase the enrichment of bacteria producing beneficial metabolites such as short-chain fatty acids, boost the production of neurotransmitters, and support the homeostasis of the gut-brain axis. In this review, we summarize the current knowledge on the role of the gut microbiota in the pathogenesis of neurodegenerative disorders with a particular focus on the benefits of LBP strains in Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis, autism, anxiety, and depression.

Microbiome alterations are associated with apolipoprotein E mutation in Octodon degus and humans with Alzheimer's disease

Gut microbiome dysbiosis is linked to many neurological disorders including Alzheimer's disease (AD). A major risk factor for AD is polymorphism in the apolipoprotein E (APOE) gene, which affects gut microbiome composition. To explore the gut-brain axis in AD, long-lived animal models of naturally developing AD-like pathologies are needed. Octodon degus (degu) exhibit spontaneous AD-like symptoms and ApoE mutations, making them suitable for studying the interplay between AD genetic determinants and gut microbiome. We analyzed the association between APOE genotype and gut microbiome in 50 humans and 32 degu using16S rRNA gene amplicon sequencing. Significant associations were found between the degu ApoE mutation and gut microbial changes in degu, notably a depletion of Ruminococcaceae and Akkermansiaceae and an enrichment of Prevotellaceae, mirroring patterns seen in people with AD. The altered taxa were previously suggested to be involved in AD, validating the degu as an unconventional model for studying the AD/microbiome crosstalk.

The involvement of effector memory CD4+ T cells in mediating the impact of genus Oscillibacter gut microbiota on Alzheimer's disease: a Mendelian randomization study

Objective

This study aimed to investigate the causal relationship between gut microbiota characteristics (207 taxa and 205 pathways) and Alzheimer's disease and determine and quantify the role of immune cells as potential mediators.

Methods

Gut microbiota characteristics (207 taxa and 205 pathways) were obtained from the NHGRI-EBI GWAS Catalog project, while Alzheimer's disease data and 731 immune cell characteristics were obtained from the IEU Open GWAS project. Two-sample Mendelian randomization (MR) was conducted to determine whether gut microbiota characteristics (207 taxa and 205 pathways) were causally related to Alzheimer's disease. Furthermore, two-step MR was employed to quantify the proportion of the effect of immune cell characteristics mediated by gut microbiota characteristics (207 taxa and 205 pathways) on Alzheimer's disease.

Results

A total of 17 immune cell characteristics were identified as potential mediators for 13 gut microbiota influencing Alzheimer's disease, with Effector Memory CD4+ T-cell Absolute Count accounted for 8.99% of the causal relationship between genus Oscillibacter and Alzheimer's disease.

Conclusion

In summary, our research confirms a causal relationship between gut microbiota and Alzheimer's disease, with immune cells contributing to a significant portion of the effect. However, the full mediators of gut microbiota's impact on Alzheimer's disease remain unclear. Further investigation is warranted to explore additional potential risk factors acting as mediators.

A preliminary study characterizing temporal changes in soil bacterial communities after dismembered bones were buried

Determining the burial time of skeletal remains is one of the most important issues of forensic medicine. We speculated that the microbiome of gravesoil may be a promising method to infer burial time by virtue of time-dependent. As we know, forensic scientists have established various models to predict the postmortem interval of a decedent based on the changes in body and soil microbiome communities. However, limited data are available on the burial time prediction for bones, especially dismembered bones. In this exploratory study, we initially conducted 16S rRNA amplicon high-throughput sequencing on the burial soil of 10 porcine femurs within a 120-day period and analyzed the changes in soil microbial communities. Compared with the control soil, a higher Shannon index in the microbial diversity of burial soil containing bones was observed. Correlation analysis identified 61 time-related bacterial families and the best subset selection method obtained best subset, containing Thermomonosporaceae, Clostridiaceae, 0319-A21, and Oxalobacteraceae, which were used to construct a simplified multiple linear regression model with a mean absolute error (MAE) of 56.69 accumulated degree day (ADD). An additional random forest model was established based on indicators for the minimum cross-validation error of Thermomonosporaceae, Clostridiaceae, 0319-A21, Oxalobacteraceae, and Syntrophobacteraceae, with an MAE of 55.65 ADD. The produced empirical data in this pilot study provided the evidence of feasibility that the microbial successional changes of burial soil will predict the burial time of dismembered bones and may also expand the current knowledge of the effects of bone burial on soil bacterial communities.

Exploring Therapeutic Potential of Phytoconstituents as a Gut Microbiota Modulator in the Management of Neurological and Psychological Disorders

The functioning of the brain and its impact on behavior, emotions, and cognition can be affected by both neurological and psychiatric disorders that impose a significant burden on global health. Phytochemicals are helpful in the treatment of several neurological and psychological disorders, including anxiety, depression, Huntington's disease (HD), Parkinson's disease (PD), Alzheimer's disease (AD), and autism spectrum disorder (ASD), because they have symptomatic benefits with few adverse reactions. Changes in gut microbiota have been associated with many neurological and psychiatric conditions. This review focuses on the potential efficacy of phytochemicals such as flavonoids, terpenoids, and polyphenols in regulating gut flora and providing symptomatic relief for a range of neurological and psychological conditions. Evidence-based research has shown the medicinal potentials of these phytochemicals, but additional study is required to determine whether altering gut microbiota might slow the advancement of neurological and psychological problems.

The effects of different lung parts, age, and batches on the lung microbiota of healthy rats

BACKGROUND

Rat models are valuable tools to study the lung microbiota in diseases. Yet the impacts of different lung parts, young and mature adult stages, and the different batches of the same conditions on the healthy rat lung microbiome have not been investigated.

METHODS

The rat lung microbiome was analyzed to clarify the lung part-dependent and age-dependent differences and to evaluate the effects of several 'batch environmental factors' on normal rats, after eliminating potential contamination.

RESULTS

The results showed that the contamination could be identified and excluded. The lung microbiome from left and right lung parts was very similar so one representative part could be used in the microbiome study. There were significantly different lung microbial communities between the young and mature adult groups, and also between the different feeding batches groups of the same repetitive feeding conditions, but a common lung microbiota characterized by Firmicutes, Bacteroidetes, Proteobacteria, and Actinobacteria as the most dominant phyla were present in all adult rats. It indicated that the experiment under the same condition of the same rats batch was needed to compare the difference in the lung microbiota and repeated experiments were necessary to confirm the results.

CONCLUSION

These data represented that the lung bacterial communities were dynamic and rapidly susceptible to environmental influence, clustered strongly by age or different feeding batches but similar in the different lung tissue parts. This study improved the basic understanding of the potential effects on the lung microbiome of healthy rats.

Palmatine improves cognitive dysfunction in Alzheimer's disease model rats through autophagy pathway and regulation of gut microbiota

Alzheimer's disease (AD) is a primary degenerative encephalopathy that first appeared as a decline in memory and learning skills. Over time, the condition's severity grew. Palmatine (Pal) alleviates Alzheimer's disease symptoms, which has neuroprotective benefits. Numerous investigations have demonstrated a close relationship among AD and gut structure changes. The aim of the research was investigating whether the improvement of Pal on AD is linked to regulating gut flora and autophagy. First, we used Aβ1-40 to induce apoptosis in HT22 cells. After Pal treatment, apoptosis can be improved. Then, We used bilateral intracranial hippocampal injection of Aβ1-40 for establishing the AD model, after treatment with Pal, the morris water maze experiment and eight-arm maze test demonstrated that Pal enhanced the AD rats' capacity for learning and memory, HE staining illustrated that Pal improved the morphological abnormalities of brain cells and gut tissue damage. Pal reduced the death of hippocampus neurons, as shown by Nissl staining. Pal substantially reduced Tau hyperphosphorylation and Aβ accumulation in the brain, according to immunohistochemical labelling. Pal improved the expression of LC3, Beclin 1, AMPK, and suppressed the expression of mTOR and P62, as validated by RT-qPCR and immunofluorescence labelling. This suggests that Pal's treatment of AD may be associated with the control of the AMPK/mTOR autophagy signalling system. 16S rRNA sequencing and short-chain fatty acids (SCFAs) content detection analysis illustrated that Pal has the potential to enhance the content of SCFAs, reverse the alterations in gut microorganisms. It has been showed by the study that Pal could improve AD by activating autophagy signaling pathway and improving gut barrier changes.

Rapid Microbial Profiling through Multimodal Biosensors for Transversal Analysis

The intricate interactions between host and microbial communities hold significant implications for biology and medicine. However, traditional microbial profiling methods face limitations in processing time, measurement of absolute abundance, detection of low biomass, discrimination between live and dead cells, and functional analysis. This study introduces a rapid multimodal microbial characterization platform, Multimodal Biosensors for Transversal Analysis (MBioTA), for capturing the taxonomy, viability, and functional genes of the microbiota. The platform incorporates single cell biosensors, scalable microwell arrays, and automated image processing for rapid transversal analysis in as few as 2 h. The multimodal biosensors simultaneously characterize the taxon, viability, and functional gene expression of individual cells. By automating the image processing workflow, the single cell analysis techniques enable the quantification of bacteria with sensitivity down to 0.0075%, showcasing its capability in detecting low biomass samples. We illustrate the applicability of the MBioTA platform through the transversal analysis of the gut microbiota composition, viability, and functionality in a familial Alzheimer's disease mouse model. The effectiveness, rapid turnaround, and scalability of the MBioTA platform will facilitate its application from basic research to clinical diagnostics, potentially revolutionizing our understanding and management of diseases associated with microbe-host interactions.

The Brain, the Eating Plate, and the Gut Microbiome: Partners in Migraine Pathogenesis

This review summarizes the relationship between diet, the gut microbiome, and migraine. Key findings reveal that certain dietary factors, such as caffeine and alcohol, can trigger migraine, while nutrients like magnesium and riboflavin may help alleviate migraine symptoms. The gut microbiome, through its influence on neuroinflammation (e.g., vagus nerve and cytokines), gut-brain signaling (e.g., gamma-aminobutyric acid), and metabolic function (e.g., short-chain fatty acids), plays a crucial role in migraine susceptibility. Migraine can also alter eating behaviors, leading to poor nutritional choices and further exacerbating the condition. Individual variability in diet and microbiome composition highlights the need for personalized dietary and prebiotic interventions. Epidemiological and clinical data support the effectiveness of tailored nutritional approaches, such as elimination diets and the inclusion of beneficial nutrients, in managing migraine. More work is needed to confirm the role of prebiotics, probiotics, and potentially fecal microbiome translation in the management of migraine. Future research should focus on large-scale studies to elucidate the underlying mechanisms of bidirectional interaction between diet and migraine and develop evidence-based clinical guidelines. Integrating dietary management, gut health optimization, and lifestyle modifications can potentially offer a holistic approach to reducing migraine frequency and severity, ultimately improving patient outcomes and quality of life.

Bacteria-organelle communication in physiology and disease

Bacteria, omnipresent in our environment and coexisting within our body, exert dual beneficial and pathogenic influences. These microorganisms engage in intricate interactions with the human body, impacting both human health and disease. Simultaneously, certain organelles within our cells share an evolutionary relationship with bacteria, particularly mitochondria, best known for their energy production role and their dynamic interaction with each other and other organelles. In recent years, communication between bacteria and mitochondria has emerged as a new mechanism for regulating the host's physiology and pathology. In this review, we delve into the dynamic communications between bacteria and host mitochondria, shedding light on their collaborative regulation of host immune response, metabolism, aging, and longevity. Additionally, we discuss bacterial interactions with other organelles, including chloroplasts, lysosomes, and the endoplasmic reticulum (ER).

Modulation of gut microbiome in the treatment of neurodegenerative diseases: A systematic review

BACKGROUND AND AIMS

Microbiota plays an essential role in maintaining body health, through positive influences on metabolic, defensive, and trophic processes and on intercellular communication. Imbalance in intestinal flora, with the proliferation of harmful bacterial species (dysbiosis) is consistently reported in chronic illnesses, including neurodegenerative diseases (ND). Correcting dysbiosis can have a beneficial impact on the symptoms and evolution of ND. This review examines the effects of microbiota modulation through administration of probiotics, prebiotics, symbiotics, or prebiotics' metabolites (postbiotics) in patients with ND like multiple sclerosis (MS), Alzheimer's disease (AD), Parkinson's disease (PD) and amyotrophic lateral sclerosis (ALS).

METHODS

PubMed, Web of Science, Medline databases and ClinicalTrials.gov registry searches were performed using pre-/pro-/postbiotics and ND-related terms. Further references were obtained by checking relevant articles.

RESULTS

Although few compared to animal studies, the human studies generally show positive effects on disease-specific symptoms, overall health, metabolic parameters, on oxidative stress and immunological markers. Therapy with probiotics in various forms (mixtures of bacterial strains, fecal microbiota transplant, diets rich in fermented foods) exert favorable effects on patients' mental health, cognition, and quality of life, targeting pathogenetic ND mechanisms and inducing reparatory mechanisms at the cellular level. More encouraging results have been observed in prebiotic/postbiotic therapy in some ND.

CONCLUSIONS

The effects of probiotic-related interventions depend on the patients' ND stage and pre-existing allopathic medication. Further studies on larger cohorts and long term comprehensive neuropsychiatric, metabolic, biochemical testing, and neuroimaging monitoring are necessary to optimize therapeutic protocols in ND.

Exploring environmental exposomes and the gut-brain nexus: Unveiling the impact of pesticide exposure

This review delves into the escalating concern of environmental pollutants and their profound impact on human health in the context of the modern surge in global diseases. The utilisation of chemicals in food production, which results in residues in food, has emerged as a major concern nowadays. By exploring the intricate relationship between environmental pollutants and gut microbiota, the study reveals a dynamic bidirectional interplay, as modifying microbiota profile influences metabolic pathways and subsequent brain functions. This review will first provide an overview of potential exposomes and their effect to gut health. This paper is then emphasis the connection of gut brain function by analysing microbiome markers with neurotoxicity responses. We then take pesticide as example of exposome to elucidate their influence to biomarkers biosynthesis pathways and subsequent brain functions. The interconnection between neuroendocrine and neuromodulators elements and the gut-brain axis emerges as a pivotal factor in regulating mental health and brain development. Thus, manipulation of gut microbiota function at the onset of stress may offer a potential avenue for the prevention and treatment for mental disorder and other neurodegenerative illness.

Butyrate as a potential therapeutic agent for neurodegenerative disorders

Maintaining an optimum microbial community within the gastrointestinal tract is intricately linked to human metabolic, immune and brain health. Disturbance to these microbial populations perturbs the production of vital bioactive compounds synthesised by the gut microbiome, such as short-chain fatty acids (SCFAs). Of the SCFAs, butyrate is known to be a major source of energy for colonocytes and has valuable effects on the maintenance of intestinal epithelium and blood brain barrier integrity, gut motility and transit, anti-inflammatory effects, and autophagy induction. Inducing endogenous butyrate production is likely to be beneficial for gut-brain homeostasis and for optimal neuronal function. For these reasons, butyrate has gained interest as a potential therapy for not only metabolic and immunological disorders, but also conditions related to the brain, including neurodegenerative diseases. While direct and indirect sources of butyrate, including prebiotics, probiotics, butyrate pro-drugs and glucosidase inhibitors, offer a promising therapeutic avenue, their efficacy and dosage in neurodegenerative conditions remain largely unknown. Here, we review current literature on effects of butyrate relevant to neuronal function, the impact of butyrate in a range of neurodegenerative diseases and related treatments that may have potential for the treatment of neurodegenerative diseases.

Short-chain fatty acids: Important components of the gut-brain axis against AD

Alzheimer's disease (AD) comprises a group of neurodegenerative disorders with some changes in the brain, which could lead to the deposition of certain proteins and result in the degeneration and death of brain cells. Patients with AD manifest primarily as cognitive decline, psychiatric symptoms, and behavioural disorders. Short-chain fatty acids (SCFAs) are a class of saturated fatty acids (SFAs) produced by gut microorganisms through the fermentation of dietary fibre ingested. SCFAs, as a significant mediator of signalling, can have diverse physiological and pathological roles in the brain through the gut-brain axis, and play a positive effect on AD via multiple pathways. Firstly, differences in SCFAs and microbial changes have been stated in AD cases of humans and mice in this paper. And then, mechanisms of three main SCFAs in treating with AD have been summarized, as well as differences of gut bacteria. Finally, functions of SCFAs played in regulating intestinal flora homeostasis, modulating the immune system, and the metabolic system, which were considered to be beneficial for the treatment of AD, have been elucidated, and the key roles of gut bacteria and SCFAs were pointed out. All in all, this paper provides an overview of SCFAs and gut bacteria in AD, and can help people to understand the importance of gut-brain axis in AD.

Gut Microbiome Multi-Omics and Cognitive Function in the Hispanic Community Health Study/Study of Latinos- Investigation of Neurocognitive Aging

INTRODUCTION

We conducted a study within the Hispanic Community Health Study/Study of Latinos- Investigation of Neurocognitive Aging (HCHS/SOL-INCA) cohort to examine the association between gut microbiome and cognitive function.

METHODS

We analyzed the fecal metagenomes of 2,471 HCHS/SOL-INCA participants to, cross-sectionally, identify microbial taxonomic and functional features associated with global cognitive function. Omnibus (PERMANOVA) and feature-wise analyses (MaAsLin2) were conducted to identify microbiome-cognition associations, and specific microbial species and pathways (Kyoto Encyclopedia of Genes and Genomes (KEGG modules) associated with cognition.

RESULTS

Eubacterium species( E. siraeum and E. eligens ), were associated with better cognition. Several KEGG modules, most strongly Ornithine, Serine biosynthesis and Urea Cycle, were associated with worse cognition.

DISCUSSION

In a large Hispanic/Latino cohort, we identified several microbial taxa and KEGG pathways associated with cognition.

An altered gut microbiome in pre-eclampsia: cause or consequence

Hypertensive disorders of pregnancy, including pre-eclampsia, are a leading cause of serious and debilitating complications that affect both the mother and the fetus. Despite the occurrence and the health implications of these disorders there is still relatively limited evidence on the molecular underpinnings of the pathophysiology. An area that has come to the fore with regard to its influence on health and disease is the microbiome. While there are several microbiome niches on and within the body, the distal end of the gut harbors the largest of these impacting on many different systems of the body including the central nervous system, the immune system, and the reproductive system. While the role of the microbiome in hypertensive disorders, including pre-eclampsia, has not been fully elucidated some studies have indicated that several of the symptoms of these disorders are linked to an altered gut microbiome. In this review, we examine both pre-eclampsia and microbiome literature to summarize the current knowledge on whether the microbiome drives the symptoms of pre-eclampsia or if the aberrant microbiome is a consequence of this condition. Despite the paucity of studies, obvious gut microbiome changes have been noted in women with pre-eclampsia and the individual symptoms associated with the condition. Yet further research is required to fully elucidate the role of the microbiome and the significance it plays in the development of the symptoms. Regardless of this, the literature highlights the potential for a microbiome targeted intervention such as dietary changes or prebiotic and probiotics to reduce the impact of some aspects of these disorders.