Tryptophan Metabolism in Alzheimer's Disease with the Involvement of Microglia and Astrocyte Crosstalk and Gut-Brain Axis

Therapeutic Mechanism of Kynurenine, a Metabolite of Probiotics, on Atopic Dermatitis in Mice

Atopic Dermatitis (AD) is a common inflammatory skin disease characterized primarily by its chronic and recurrent nature. This has a significant impact on productivity and human longevity. Dysbiosis of gut flora has been demonstrated to be significantly associated with the progression of AD. In our previous research, it was shown that Lactobacillus rhamnosus RL5-H3-005 (RL) and Pediococcus acidilactici RP-H3-006 (RP) have the ability to reduce the risk of disease in AD mice through the gut-mammary axis. Based on our previous work, this study aims to further investigate the effects of kynurenine (KYN), a metabolite of RL and RP, on AD mice induced by 2, 4-dinitrofluorobenzene (DNFB). In this study, we found that supplementing KYN in AD mice effectively alleviates the pathological symptoms of atopic dermatitis and further improves the levels of SCFAs in their intestines. Further research indicates that KYN's therapeutic effects on AD are primarily manifested in the reduction of secretory immunoglobulin A (sIgA), immunoglobulin E (IgE), interleukin-4 (IL-4), IL-5, IL-13, and thymic stromal lymphopoietin (TSLP) levels in mice, while also repairing the intestinal barrier function of AD mice. Overall, the metabolites KYN of probiotics RL and RP can regulate the levels of SCFAs of mice, potentially improving the symptoms of AD mice through the gut-skin axis.

Transcriptome analysis reveals that the injection of mesenchymal stem cells remodels extracellular matrix and complement components of the brain through PI3K/AKT/FOXO1 signaling pathway in a neuroinflammation mouse model

Neurological disorders are often accompanied by neuroinflammatory responses. Our previous research indicated that mesenchymal stem cells (MSCs) suppressed neuroinflammation in the brain. The mechanism of action remains not fully understood. In this study, we analyzed the impact of injected MSCs on the transcriptome in the brains of neuroinflammatory mouse model (NIM) with bioinformatical methods and conducted experimental validation with qPCR and Western blot. The results showed that the expression of extracellular matrix components changed, and the complement cascade was activated in the NIM brains. Injection of MSCs reversed the expression of ECM components and inhibited complement activation. MSCs may promote the improvement of neuronal synaptic function and alter the infiltration of immune cells into the brain. MSCs regulated the PI3K/AKT/Foxo1 signaling pathway. These findings will be very helpful for the development of MSCs-based therapy and the treatment of neuroinflammation-related diseases.

Could a Mediterranean Diet Modulate Alzheimer's Disease Progression? The Role of Gut Microbiota and Metabolite Signatures in Neurodegeneration

Neurodegenerative disorders such as Alzheimer's disease (AD), the most common form of dementia, represent a growing global health crisis, yet current treatment strategies remain primarily palliative. Recent studies have shown that neurodegeneration through complex interactions within the gut-brain axis largely depends on the gut microbiota and its metabolites. This review explores the intricate molecular mechanisms linking gut microbiota dysbiosis to cognitive decline, emphasizing the impact of microbial metabolites, including short-chain fatty acids (SCFAs), bile acids, and tryptophan metabolites, on neuroinflammation, blood-brain barrier (BBB) integrity, and amyloid-β and tau pathology. The paper highlights major microbiome signatures associated with Alzheimer's disease, detailing their metabolic pathways and inflammatory crosstalk. Dietary interventions have shown promise in modulating gut microbiota composition, potentially mitigating neurodegenerative processes. This review critically examines the influence of dietary patterns, such as the Mediterranean and Western diets, on microbiota-mediated neuroprotection. Bioactive compounds like prebiotics, omega-3 fatty acids, and polyphenols exhibit neuroprotective effects by modulating gut microbiota and reducing neuroinflammation. Furthermore, it discusses emerging microbiome-based therapeutic strategies, including probiotics, prebiotics, postbiotics, and fecal microbiota transplantation (FMT), as potential interventions for slowing Alzheimer's progression. Despite these advances, several knowledge gaps remain, including interindividual variability in microbiome responses to dietary interventions and the need for large-scale, longitudinal studies. The study proposes an integrative, precision medicine approach, incorporating microbiome science into Alzheimer's treatment paradigms. Ultimately, cognizance of the gut-brain axis at a mechanistic level could unlock novel therapeutic avenues, offering a non-invasive, diet-based strategy for managing neurodegeneration and improving cognitive health.

Gut-lung Axis mediates asthma pathogenesis: Roles of dietary patterns and their impact on the gut microbiota

The gut-lung axis, a vital signaling network linking the gastrointestinal and pulmonary systems, regulates immune responses and the progression of respiratory diseases. Nutritional components can modulate the gut microbiome and regulate the synthesis of critical intestinal microbial metabolites, which are essential for maintaining immune homeostasis and supporting respiratory health. Conversely, poor dietary habits exacerbate asthma and other respiratory conditions through the modulation of systemic inflammation and immune responses. Dietary interventions, such as the Mediterranean diet, are reported to restore microbial balance and improve respiratory health by increasing the production of anti-inflammatory metabolites, potentiating immune responses, and preserving epithelial barrier integrity. In contrast, Western dietary patterns, which are characterized by high fat and low fiber intake, disrupt microbial diversity, resulting in increased levels of pro-inflammatory metabolites that aggravate airway inflammation and asthma severity. This review aimed to elucidate the mechanisms underlying the regulatory effects of gut microbes and their metabolites on asthma. Additionally, previous findings related to the gut-lung axis have been summarized, providing insights into potential therapeutic strategies for asthma management.

Neutrophil extracellular traps (NETs) and NETosis in alcohol-associated diseases: A systematic review

Heavy alcohol consumption is implicated in the alteration of the antimicrobial function of neutrophils, such as phagocytosis, chemotaxis, the formation of neutrophil extracellular traps (NETs), and the occurrence of NETosis. NETosis is an endogenous process of elimination of invading microbes, autoantibodies, and inflammatory elements such as danger-associated molecular patterns (DAMPs) and pathogen-associated patterns (PAMPs). However, both exaggeration and suppression of NETosis modulate normal physiological and metabolic processes by influencing events at the molecular and cellular levels. Recent research shows that binge alcohol consumption induces NETosis, leading to tissue damage and inflammation. Binge alcohol consumption, chronic alcohol intake, and alcohol use disorder (AUD) can affect immunity and often lead to alcohol-associated liver disease (ALD) and/or other organ damage. Alcohol can lead to detrimental consequences in multiple organs, including the brain, liver, pancreas, and gut. Gut-derived microbial substances, such as endotoxins in the circulation, induce systemic inflammation. Sterile danger signals from damaged cells, cytokines, and prostaglandins act as proinflammatory stimuli and are involved in multiple signaling pathways. The alcohol-induced proinflammatory cytokines chemoattract neutrophils, which interact and coordinate with other immune cells to exaggerate or suppress inflammation within the inflammatory milieu, depending on the alcohol effects. Several proteins, including different receptors, play important roles in the activation and formation of NETs as well as the initiation and execution of NETosis. This review article specifically gathers the current information on NETosis, its biological components, and signaling pathways relating to the formation of NETs and the occurrence of NETosis associated with ALD and AUD in multiorgans, specifically in the brain, liver, and gut. We also briefly describe various therapeutic strategies against AUD-associated NETosis in experimental models and human disease states.

Postbiotics as a therapeutic tool in Alzheimer's disease: Insights into molecular pathways and neuroprotective effects

Alzheimer's disease (AD) is a progressive neurodegenerative disease, characterized by oxidative stress, neuroinflammation, mitochondrial dysfunction, neurotransmitter imbalance, tau hyperphosphorylation, and amyloid beta (Aβ) accumulation in brain regions. The gut microbiota (GM) has a major impact on brain function due to its bidirectional interaction with the gut through the gut-brain axis. The gut dysbiosis has been associated with neurological disorders, emphasizing the importance of gut homeostasis in maintaining appropriate brain function. The changes in the composition of microbiomes influence neuroinflammation and Aβ accumulation by releasing pro-inflammatory cytokines, decreasing gut and blood-brain barrier (BBB) integrity, and microglial activation in the brain. Postbiotics, are bioactive compounds produced after fermentation, have been shown to provide several health benefits, particularly in terms of neuroinflammation and cognitive alterations associated with AD. Several research studies on animal models and human have successfully proven the effects of postbiotics on enhancing cognition and memory in experimental animals. This article explores the protective effects of postbiotics on cellular mechanisms responsible for AD pathogenesis and studies highlighting the influence of postbiotics as a total combination and specific compounds, including short-chain fatty acids (SCFAs). In addition, postbiotics act as a promising option for future research to deal with AD's progressive nature and improve an individual's life quality using microbiota modulation.

Foods for Sleep Improvement: A Review of the Potential and Mechanisms Involved

Insomnia affects one-third of the world's population; the negative effects of insomnia are significant, and traditional insomnia medications have numerous side effects and cause considerable suffering. This has aroused interest in obtaining sleep-improving substances from foods. This study conducted a comprehensive literature review using Web of Science and PubMed with keywords like "sleep", "insomnia", and "food". A subsequent summary of the literature revealed that certain foods, including milk, Ziziphus jujuba, Lactuca sativa, ginseng, Schisandra chinensis, and Juglans regia, etc., are purported to enhance sleep quality by prolonging sleep duration, reducing sleep latency, and alleviating anxiety. The mechanisms of these foods' effects mainly occur via the central nervous system, particularly the gamma-aminobutyric acid (GABA)ergic and 5-hydroxytryptamine (5-HT)ergic systems. Although this review supports the fact that they have potential, further research is needed. There are also issues such as more limited foods, fewer mechanisms, fewer pharmacokinetic studies, and more traditional research models being involved. These need to be addressed in the future to adequately address the problem of insomnia. It is hoped that this study will contribute to research into foods with sleep-improving properties and, in the future, provide an effective natural alternative for those seeking medication.

Psychedelics in neuroinflammation: Mechanisms and therapeutic potential

Neuroinflammation is a critical factor in the pathogenesis of various neurodegenerative and psychiatric disorders, including Alzheimer's disease, Parkinson's disease, and major depressive disorder. Psychedelics, such as psilocybin, lysergic acid diethylamide (LSD), and dimethyltryptamine (DMT), have demonstrated promising therapeutic effects on neuroinflammation, primarily through interactions with serotonin (5-HT) receptors, particularly the 5-HT2A receptor. Activation of these receptors by psychedelics modulates the production of pro-inflammatory cytokines, regulates microglial activity, and shifts the balance between neurotoxic and neuroprotective metabolites. Additionally, psychedelics affect critical signaling pathways, including the nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB), phosphatidylinositol-3-kinase/protein kinase B (PI3K/Akt), and mechanistic target of rapamycin (mTOR) pathways, promoting neuroplasticity and exerting anti-inflammatory effects. Beyond the serotonergic system, other neurotransmitter systems-including the glutamatergic, dopaminergic, noradrenergic, gamma-aminobutyric acid (GABAergic), and cholinergic systems-also play significant roles in mediating the effects of psychedelics. This review examines the intricate mechanisms by which psychedelics modulate neuroinflammation and underscores their potential as innovative therapeutic agents for treating neuroinflammatory and neuropsychiatric disorders.

Differences in plasma metabolome between non-Hispanic White and non-Hispanic Black women

BACKGROUND

To understand potential racial differences in disease susceptibility and develop targeted prevention strategies, it is essential to establish biological differences between racial groups in healthy individuals. However, knowledge about how race impacts metabolites is limited. We therefore performed a cross-sectional study using comprehensive metabolomics analysis to investigate racial differences in metabolites among 506 non-Hispanic White (NHW) women and 163 non-Hispanic Black (NHB) women.

METHODS

We performed untargeted plasma metabolomic profiling using Metabolon's platform (Durham, NC®) and identified 1074 metabolites in 9 super-pathways. We used multivariable linear regression models, adjusted for confounders, to identify associations between race and metabolites. We applied a Bonferroni correction (p-value < 10-5) to account for multiple testing.

RESULTS

We identified 26 metabolites that differed significantly between NHW and NHB women. Seven, 10, 17, and 23 metabolites showed absolute percentage differences ≥ 50, ≥ 40%, ≥ 30%, and ≥ 20%, respectively. Xenobiotics (n = 5) and amino acids (n = 2) exhibited the largest absolute percentage differences (≥ 50%) between NHB and NHW women. In the xenobiotics super-pathway, NHB women had higher thymol sulfate, 2-naphthol sulfate, and 2-hydroxyfluorene sulfate, derived from the exposure to polycyclic aromatic hydrocarbons, while NHW women had higher xanthine metabolites. In the amino acid super-pathway, lysine and tryptophan metabolites were lower in NHB women.

CONCLUSIONS

We report differences in several metabolites between NHW and NHB women. These findings require validation in a different study and could provide insight into investigating how racial differences in metabolites may impact disease burden across diverse populations.

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.

Neuroprotective Effect of 1α,25-Dihydroxyvitamin D3 Against Cognitive Impairment in d-Galactose-Induced Aging Mice

Aging and age-related cognitive impairment have emerged as a growing global public health concern, yet there are no effective preventive strategies. Excessive oxidative stress and neuroinflammation have been proven to contribute to cognitive decline. Vitamin D maintains the redox balance and exerts immunomodulatory effects, but the specific role of vitamin D in aging and age-related cognitive impairment remains elusive. This study explored the neuroprotective effects and the potential molecular mechanisms of 1α,25-dihydroxyvitamin D3 in the aging model. An aging model was established by the treatment of d-galactose for 14 weeks in male KM mice. 0.1, 0.5, or 1 μg/kg 1α,25-dihydroxyvitamin D3 were used in the intervention group for 8 weeks. Cognitive performance was evaluated using the Morris water maze test, and the levels of oxidative stress and neuroinflammation in the hippocampus were further analyzed. d-galactose induced memory impairment, whereas 1α,25-dihydroxyvitamin D3 intervention prevented cognitive decline, accompanied by a reduction in neuronal apoptosis, an enhancement of synaptic plasticity, and a decrease in Aβ deposition. Meanwhile, 1α,25-dihydroxyvitamin D3 dramatically attenuated oxidative stress, mitigated microglial cell activation, and ameliorated neuroinflammation by activating the nuclear factor erythroid 2-related factor 2 (Nrf2)/antioxidant response elements (AREs) axis and inhibiting the NF-κB signaling pathway. This study provides evidence that 1α,25-dihydroxyvitamin D3 might be a promising nutritional strategy for preventing cognitive decline in aging, thereby facilitating the clinical application and expanding the insight of vitamin D.

Can consumption of finger millet diet improve mental health status in athletes: a possible link with modulation of cortisol levels

PURPOSE

Despite the promising health benefits of finger millet, there is a notable lack of research specifically examining its effects on athletes' mental health. Therefore, the present narrative review aimed to explore the potential of finger millet (Eleusine coracana) in enhancing the mental health status of athletes.

METHODS

For this narrative review databases like "PubMed," "SPORTDiscus," "Scopus," "ProQuest" and "Google Scholar" were referred to identify and analyze the studies to determine their relevance and findings.

RESULTS

Studies have shown that nutritional intervention has a significant impact on mental health through improved mood, cognitive function, and overall well-being. Finger millet is a valuable reservoir of vital nutrients , including amino acids, vitamins, minerals, and antioxidants, which play crucial roles in reducing oxidative stress and cortisol levels, which are key factors in mental health disorders. Furthermore, low glycemic index and high dietary fiber content of finger millet contribute to stable blood sugar levels, which are crucial for maintaining mental stability and preventing stress-induced cortisol spikes. Dietary fiber in finger millet also helps in boosting the gut microbiota, which helps in stimulating mental and cognitive health through the gut-brain axis.

CONCLUSION

Given the physical and psychological demands on athletes, incorporating finger millet into their diets could offer a holistic approach for improving both performance and mental well-being. Despite these promising findings, the specific effect of finger millet on athletes' mental health remains unclear. This review highlights the need for more focused research on this topic, emphasizing the potential of finger millet as a na-t ural dietary intervention to enhance mental health and stress management in athletes. We conclude by calling for more comprehensive studies to fully understand the mechanisms and benefits of finger millet in athletic populations, aiming to bridge the current gap in the literature and pave the way for evidence-based dietary recommendations.

Caveolae with serotonin and NMDA receptors as promising targets for the treatment of Alzheimer's disease

Alzheimer's disease is the most general type of cognitive impairments. Until recently, strategies that prevent its clinical progression have remained more elusive. Consequently, research direction should be for finding effective neuroprotective agents. It has been suggested oxidative stress, mitochondrial injury, and inflammation level might lead to brain cell death in many neurological disorders. Therefore, several autophagy-targeted bioactive compounds may be promising candidate therapeutics for the prevention of brain cell damage. Interestingly, some risk genes to Alzheimer's disease are expressed within brain cells, which may be linked to cholesterol metabolism, lipid transport, endocytosis, exocytosis and/or caveolae formation, suggesting that caveolae may be a fruitful therapeutic target to improve cognitive impairments. This review would highlight the latest advances in therapeutic technologies to improve the treatment of Alzheimer's disease. In particular, a paradigm that serotonin and N-methyl-d-aspartate (NMDA) receptors agonist/antagonist within caveolae structure might possibly improve the cognitive impairment. Consequently, cellular membrane biophysics should improve our understanding of the pathology of the cognitive dysfunction associated with Alzheimer's disease. Here, this research direction for the purpose of therapy may open the potential to move a clinical care toward disease-modifying treatment strategies with certain benefits for patients.

Tryptophan Metabolism Disorder-Triggered Diseases, Mechanisms, and Therapeutic Strategies: A Scientometric Review

BACKGROUND

Tryptophan is widely present in foods such as peanuts, milk, and bananas, playing a crucial role in maintaining metabolic homeostasis in health and disease. Tryptophan metabolism is involved in the development and progression of immune, nervous, and digestive system diseases. Although some excellent reviews on tryptophan metabolism exist, there has been no systematic scientometric study as of yet.

METHODS

This review provides and summarizes research hotspots and potential future directions by analyzing annual publications, topics, keywords, and highly cited papers sourced from Web of Science spanning 1964 to 2022.

RESULTS

This review provides a scientometric overview of tryptophan metabolism disorder-triggered diseases, mechanisms, and therapeutic strategies.

CONCLUSIONS

The gut microbiota regulates gut permeability, inflammation, and host immunity by directly converting tryptophan to indole and its derivatives. Gut microbial metabolites regulate tryptophan metabolism by activating specific receptors or enzymes. Additionally, the kynurenine (KYN) pathway, activated by indoleamine-2, 3-dioxygenase (IDO) and tryptophan 2, 3-dioxygenase, affects the migration and invasion of glioma cells and the development of COVID-19 and depression. The research and development of IDO inhibitors help to improve the effectiveness of immunotherapy. Tryptophan metabolites as potential markers are used for disease therapy, guiding clinical decision-making. Tryptophan metabolites serve as targets to provide a new promising strategy for neuroprotective/neurotoxic imbalance affecting brain structure and function. In summary, this review provides valuable guidance for the basic research and clinical application of tryptophan metabolism.