Sodium butyrate alleviates lead-induced neuroinflammation and improves cognitive and memory impairment through the ACSS2/H3K9ac/BDNF pathway

Archaea methanogens are associated with cognitive performance through the shaping of gut microbiota, butyrate and histidine metabolism

The relationship between bacteria, cognitive function and obesity is well established, yet the role of archaeal species remains underexplored. We used shotgun metagenomics and neuropsychological tests to identify microbial species associated with cognition in a discovery cohort (IRONMET, n = 125). Interestingly, methanogen archaeas exhibited the strongest positive associations with cognition, particularly Methanobrevibacter smithii (M. smithii). Stratifying individuals by median-centered log ratios (CLR) of M. smithii (low and high M. smithii groups: LMs and HMs) revealed that HMs exhibited better cognition and distinct gut bacterial profiles (PERMANOVA p = 0.001), characterized by increased levels of Verrucomicrobia, Synergistetes and Lentisphaerae species and reduced levels of Bacteroidetes and Proteobacteria. Several of these species were linked to the cognitive test scores. These findings were replicated in a large-scale validation cohort (Aging Imageomics, n = 942). Functional analyses revealed an enrichment of energy, butyrate, and bile acid metabolism in HMs in both cohorts. Global plasma metabolomics by CIL LC-MS in IRONMET identified an enrichment of methylhistidine, phenylacetate, alpha-linolenic and linoleic acid, and secondary bile acid metabolism associated with increased levels of 3-methylhistidine, phenylacetylgluamine, adrenic acid, and isolithocholic acid in the HMs group. Phenylacetate and linoleic acid metabolism also emerged in the Aging Imageomics cohort performing untargeted HPLC-ESI-MS/MS metabolic profiling, while a targeted bile acid profiling identified again isolithocholic acid as one of the most significant bile acid increased in the HMs. 3-Methylhistidine levels were also associated with intense physical activity in a second validation cohort (IRONMET-CGM, n = 116). Finally, FMT from HMs donors improved cognitive flexibility, reduced weight, and altered SCFAs, histidine-, linoleic acid- and phenylalanine-related metabolites in the dorsal striatum of recipient mice. M. smithii seems to interact with the bacterial ecosystem affecting butyrate, histidine, phenylalanine, and linoleic acid metabolism with a positive impact on cognition, constituting a promising therapeutic target to enhance cognitive performance, especially in subjects with obesity.

Emerging roles of histone modifications in environmental toxicants-induced neurotoxicity

Epigenetics describes itself as heritable modifications in gene function that eventually alter gene and protein expression levels without any alterations in the genome sequence. Epigenetic alterations are closely association with several neurological diseases and neurodevelopmental disorders. In recent years, growing shreds of evidences suggested the crucial role of epigenetic modifications especially histone modifications in environmental toxicants-induced neurotoxicity. This review will give an overview of the state of knowledge on histone alterations and the ways in which environmental pollutants bisphenol-A, heavy metals, pesticides, and phthalates affects post-translational modifications to alter gene transcription and cause neurological abnormalities. We provide a brief summary of the results of recent research on the effects of environmental toxins on each of the prior identified processes of histone modifications, including the neurological consequences and changes in histones. There is also discussion of the limitations of current research findings. Furthermore, this review aims to provide viewers a comprehensive knowledge regarding the role of histone modifications in various environmental toxicants-induced neurological diseases and offers insights for future research.

Gut microbiota regulate insomnia-like behaviors via gut-brain metabolic axis

Sleep interacts reciprocally with the gut microbiota. However, mechanisms of the gut microbe-brain metabolic axis that are responsible for sleep behavior have remained largely unknown. Here, we showed that the absence of the gut microbiota can alter sleep behavior. Sleep deprivation reduced butyrate levels in fecal content and the hypothalamus in specific pathogen-free mice but not in germ-free mice. The microbial metabolite butyrate can promote sleep by modulating orexin neuronal activity in the lateral hypothalamic area in mice. Insomnia patients had lower serum butyrate levels and a deficiency in butyrate-producing species within the gut microbiota. Transplantation of the gut microbiota from insomnia patients to germ-free mice conferred insomnia-like behaviors, accompanied by a decrease in serum butyrate levels. The oral administration of butyrate rescued sleep disturbances in recipient mice. Overall, these findings reveal the causal role of microbial metabolic pathways in modulating insomnia-like behaviors, suggesting potential therapeutic strategies for treating sleep disorders.

Elucidating the specific mechanisms of the gut-brain axis: the short-chain fatty acids-microglia pathway

In recent years, the gut microbiota has been increasingly recognized for its influence on various central nervous system diseases mediated by microglia, yet the underlying mechanisms remain unclear. As key metabolites of the gut microbiota, short-chain fatty acids (SCFAs) have emerged as a focal point in understanding microglia-related interactions. In this review, we further refine the connection between the gut microbiota and microglia by introducing the concept of the "SCFAs-microglia" pathway. We summarize current knowledge on this pathway, recent discoveries regarding its role in neurological diseases, and potential pharmacological strategies targeting it. Finally, we outlined the current challenges and limitations in this field of research. We hope this review provides new insights into the role of the gut microbiota in neuroimmune regulation.

Flavanones as Modulators of Gut Microbiota and Cognitive Function

Flavanones, a key subclass of flavonoids, exhibit a wide range of biological activities, including antioxidant, anti-inflammatory, and neuroprotective properties. Predominantly found in citrus fruits, they occur in both aglycone and glycosylated forms, undergoing extensive metabolic transformation upon ingestion. Recent evidence suggests that flavanones, such as naringenin and hesperidin, influence gut microbiota composition, fostering a balance between beneficial and pathogenic bacterial populations. The gut microbiota plays a pivotal role in regulating the gut-brain axis, impacting cognitive function through the production of short-chain fatty acids (SCFAs), neurotransmitters, and anti-inflammatory cytokines. The modulation of the gut microbiome by flavanones has been associated with improvements in cognitive performance and a reduced risk of neurodegenerative disorders. This review provides a comprehensive analysis of the characteristics of major flavanones, their metabolic pathways, and their impact on gut microbiota and cognitive function. It covers the fundamental mechanisms through which flavanones exert their effects, as well as their potential therapeutic applications for brain health and neuroprotection. Despite promising findings, further research is needed to determine optimal dosages, strategies to enhance bioavailability, and long-term safety profiles.

Changes of intestinal microbiome and its relationship with painful diabetic neuropathy in rats

OBJECTIVE

To analyze the gut bacterial microbiome in rats with painful diabetic neuropathy (PDN) compared to normal rats.

METHODS

Type 2 diabetes was induced in rats via a high-fat and high-sugar diet combined with a low dose of streptozotocin. Glucose metabolism and insulin sensitivity were evaluated using intraperitoneal glucose tolerance tests and insulin tolerance tests. The progression of peripheral neuropathy was assessed using the mechanical withdrawal threshold and thermal withdrawal latency. Histopathological analysis of rat colon tissues was performed using hematoxylin-eosin staining to observe morphological changes. The expression levels of pro-inflammatory cytokines TNF-α and IL-1β in spinal cord tissues were measured using enzyme-linked immunosorbent assay (ELISA). Fecal samples were then collected for metagenomic sequencing and analysis.

RESULT

Behavioral tests revealed reduced mechanical withdrawal threshold and thermal withdrawal latency in PDN rats. Histological analysis showed significant colonic mucosal damage and inflammatory cell infiltration, suggesting impaired intestinal barrier function. Elevated TNF-α and IL-1β levels in spinal cord tissues further highlight peripheral inflammation's role in PDN. Sequencing analysis revealed significant differences in gut microbiota composition between PDN and control rats, with altered Bacillota/Bacteroidota ratios and increased Lactobacillus abundance. Functional annotation analysis, based on the KEGG, EggNOG, and CAZy databases, indicated significant enrichment of metabolic pathways related to carbohydrate and amino acid metabolism, energy metabolism, and cell structure biogenesis in PDN rats. Cluster analysis identified higher functional clustering in Metabolism and Genetic Information Processing pathways in PDN rats.

CONCLUSION

This study demonstrates that PDN leads to altered gut microbiota composition, disrupted metabolic pathways, and increased inflammation, contributing to the pathological progression of diabetic neuropathy. This study provides new insights into the interplay between gut microbiota and diabetic neuropathy, offering potential avenues for therapeutic interventions targeting microbiome and metabolism.

Single-Nucleus Transcriptomics Reveals Prenatal and Postnatal Pb Exposure-Induced Cell-Specific Neurotoxicity and Dysregulated Microglia-Neuron Communication in Mice Brain

Lead (Pb) is an environmental pollutant that has lasting effects on neurodevelopment. Children exhibit heightened sensitivity to Pb exposure compared to adults, and prenatal Pb exposure can harm the developing fetal nervous system. However, the specific regulatory effects of Pb across various developmental stages are not well understood. This study employed single-nucleus RNA sequencing (snRNA-seq) to analyze mice brains at different ages (2 and 8 weeks) following prenatal and postnatal Pb exposure. Blood lead level in exposed mice is comparable to those detected in human samples, implying its environmental implication. A total of 43,303 brain cells were sequenced for cell-specific analysis. Pb exposure was found to elevate the proportion of immature neurons in the brains of 2 week-old mice and to perturb neurodevelopment- and neural structure-related pathways within neurons. In 8 week-old mice, Pb primarily influenced pathways implicated in synaptic transmission, signal transduction, and learning and memory in both neurons and glial cells. The communication involving neurotransmitters glutamate and γ-aminobutyric acid (GABA), along with their receptors, was disrupted between neuron and microglia. Through the application of snRNA-seq, this study has demonstrated that the Pb-induced neurotoxicity is characterized by cellular heterogeneity and the disruption of neurotransmitter-related communication between microglia and neurons could be a critical factor in Pb-induced neurotoxicity.

Short-Chain Fatty Acids Alleviate Perioperative Neurocognitive Disorders Through BDNF/PI3K/Akt Pathway in Middle-Aged Rats

Perioperative neurocognitive disorders (PND), characterized by persistent cognitive impairment lasting from days to years, present substantial clinical challenges in elderly surgical populations, profoundly compromising functional independence, quality of life, and long-term prognosis. We aimed to investigate the effects of short-chain fatty acids (SCFAs) treatment on PND via mediating Brain-derived neurotrophic factor (BDNF)/Phosphatidylinositol3-kinase (PI3K)/Protein kinase B (Akt) pathway. Using 16S rDNA sequencing targeting the V3-V4 hypervariable regions, we first demonstrated significant gut microbiota dysbiosis in PND model rats, accompanied by altered SCFAs profiles. Subsequent fecal microbiota transplantation (FMT) experiments established causal relationships between PND-associated microbial alterations and spatial cognitive deficits. Mechanistically, SCFAs supplementation attenuated neuronal damage and restored synaptic plasticity, as evidenced by Nissl staining quantification (reduced chromatolysis), TUNEL assay (decreased apoptosis rate), and immunohistochemical analysis (upregulated NeuN expression). Molecular investigations revealed that SCFAs-mediated cognitive improvement involved BDNF upregulation and subsequent PI3K/Akt pathway activation, ultimately enhancing neuronal survival and synaptic integrity. Notably, PND animals exhibited characteristic neuropathological features including synaptic density reduction (PSD-95 downregulation), neuroinflammation amplification (IL-6 elevation), and apoptosis activation-all significantly reversed by SCFA intervention. Our findings establish a novel gut-brain axis mechanism wherein microbiota-derived SCFAs may exert neuroprotection through BDNF-dependent PI3K/Akt signaling, and offer potential therapeutic strategies for PND management.

Honeybees fed D-galactose exhibit aging signs with changes in gut microbiota and metabolism

Honeybees (Apis mellifera), as social insects, exhibit complex social behaviors and cognitive functions. The short lifespan and stable gut microorganisms of honeybees provide certain availability as a rapid and high-flux animal model for aging research. This study explored the effect of D-galactose, a common aging inducer, on honeybees and investigated the associated effects and mechanisms, with particular focus on the potential protective role of sodium butyrate. Experimental cohorts were established as follows: conventional (CV) group, D-galactose-treated (DG) group, and sodium butyrate-treated (SB) group. The CV group was fed sucrose solution; the DG group was fed D-galactose solution; and the SB group was fed D-galactose and sodium butyrate solution. A comprehensive assessment was conducted on day 15 post-treatment, including survival analysis, starvation test, motor, learning and memory ability tests, malondialdehyde test, and Smurf test. Potential mechanisms through the microbiome and metabolome were investigated. Compared to the honeybees from the CV group, those in the DG group showed a shortened lifespan, a weaker energy storage ability, impaired motor, learning, and memory abilities, reduced weight, increased oxidation, and a disrupted gut barrier. These phenotypic changes were associated with microbial dysbiosis characterized by Lactobacillus enrichment and diminished butyrate levels. Notably, sodium butyrate supplementation extended the honeybees' lifespan and improved their learning and memory abilities damaged by D-galactose. Our findings establish honeybees as a valuable model system for aging research and highlight the crucial role of butyrate metabolism in senescence regulation.IMPORTANCEThis study presents a novel approach to investigating aging processes by establishing a D-galactose-induced aging model in honeybees. Our findings demonstrate that butyrate supplementation effectively attenuates D-galactose-induced senescence phenotypes, suggesting its potential as a therapeutic intervention for age-related decline. This research provides a unique model system for aging studies and highlights the significant role of butyrate in modulating senescence progression. The results contribute to our understanding of the molecular mechanisms underlying aging and offer new insights into potential anti-aging strategies.

Interplay of Neuroinflammation and Gut Microbiota Dysbiosis in Alzheimer's Disease Using Diffusion Kurtosis Imaging Biomarker in 3 × Tg-AD Mouse Models

The relationship between alterations in brain microstructure and dysbiosis of gut microbiota in Alzheimer's disease (AD) has garnered increasing attention, although the functional implications of these changes are not yet fully elucidated. This research examines how neuroinflammation, systemic inflammation, and gut microbiota interact in male 3 × Tg-AD and B6129SF1/J wild-type (WT) mice at 6 months-old (6-MO) and 12 months-old (12-MO). Employing a combination of behavioral assessments, diffusion kurtosis imaging (DKI), microbiota profiling, cytokine analysis, short-chain fatty acids (SCFAs), and immunohistochemistry, we explored the progression of AD-related pathology. Significant memory impairments in AD mice at both assessed ages were correlated with altered DKI parameters that suggest neuroinflammation and microstructural damage. We observed elevated levels of pro-inflammatory cytokines, such as IL-1β, IL-6, TNFα, and IFN-γ, in the serum, which were associated with increased activity of microglia and astrocytes in brain regions critical for memory. Although gut microbiota analysis did not reveal significant changes in alpha diversity, it did show notable differences in beta diversity and a diminished Firmicutes/Bacteroidetes (F/B) ratio in AD mice at 12-MO. Furthermore, a reduction in six kinds of SCFAs were identified at two time points of 6-MO and 12-MO, indicating widespread disruption in gut microbial metabolism. These findings underscore a complex bidirectional relationship between systemic inflammation and gut dysbiosis in AD, highlighting the gut-brain axis as a crucial factor in disease progression. This study emphasizes the potential of integrating DKI metrics, microbiota profiling, and SCFA analysis to enhance our understanding of AD pathology and to identify new therapeutic targets.

Higher dietary butyrate intake is associated with better cognitive function in older adults: evidence from a cross-sectional study

Background

Studies indicate that butyrate can enhance memory and cognitive functions in mice by inhibiting neuroinflammation and neuronal apoptosis. Elevated fecal butyrate levels in older individuals with mild cognitive impairment correlate with reduced levels of Aβ-42, an Alzheimer's disease biomarker. This study investigated the relationship between butyrate consumption and cognitive performance in older adults, which remains to be elucidated.

Methods

This study employed a cross-sectional, observational design to analyze data gathered from 2,078 participants enrolled in the 2011-2014 US National Health and Nutrition Examination Survey (NHANES). Butyrate intake was determined based on two 24-h dietary assessments. To evaluate cognitive function, three tests were administered: the Animal Fluency Test (AFT) to assess executive function, the Digit Symbol Substitution Test (DSST) for measuring processing speed, and the Consortium to Establish a Registry for Alzheimer's disease (CERAD) subtest for assessing memory. Z scores were computed for each test and overall cognitive performance. Multivariate linear regression models and a generalized additive model (GAM) were used to examine the correlation between butyrate consumption and mental functions. Finally, subgroup analyses and interaction tests were used to verify the robustness of the associations.

Results

The NHANES study encompasses two surveys conducted between 2011 and 2014 that involved 2,078 participants aged 60 years or older. Higher dietary butyrate consumption had a positive correlation between superior performance on DSST, AFT, CERAD-Immediate Recall Test, and Z scores. The participants in the upper quartile of butyrate intake had significantly higher DSST (β = 1.60, 95% CI: 0.04-3.17), AFT scores (β = 0.99, 95% CI: 0.37-1.60), and Z scores (β = 0.09, 95% CI: 0.01-0.17) than individuals in the lowest quartile even after adjusting for potential confounders. Finally, no notable interactions were observed within the groupings. Finally, in subgroup analyses, BMI was found to influence the positive association between butyrate and DSST with Z score, and hypertension also influenced the association between butyrate and DSST.

Conclusion

Higher butyrate intake in individuals aged ≥60 years was linked to better cognitive functioning. This could potentially contribute to maintaining brain function during aging.

Perturbations in the microbiota-gut-brain axis shaped by social status loss

Social status is closely linked to physiological and psychological states. Loss of social dominance can lead to brain disorders such as depression, but the underlying mechanisms remain unclear. The gut microbiota can sense stress and contribute to brain disorders via the microbiota-gut-brain axis (MGBA). Here, using a forced loss paradigm to demote dominant mice to subordinate ranks, we find that stress alters the composition and function of the gut microbiota, increasing Muribaculaceae abundance and enhancing butanoate metabolism, and gut microbial depletion resists forced loss-induced hierarchical demotion and behavioral alteration. Single-nucleus transcriptomic analysis of the prefrontal cortex (PFC) indicates that social status loss primarily affected interneurons, altering GABAergic synaptic transmission. Weighted gene co-expression network analysis (WGCNA) reveals modules linked to forced loss in the gut microbiota, colon, PFC, and PFC interneurons, suggesting changes in the PI3K-Akt signaling pathway and the glutamatergic synapse. Our findings provide evidence for MGBA perturbations induced by social status loss, offering potential intervention targets for related brain disorders.

Effects of Chlorpyrifos on gut dysbiosis and barriers integrity in women with a focus on pregnancy and prebiotic intervention: Insights from advanced in vitro human models

Chlorpyrifos (CPF), a commonly used organophosphate pesticide, poses potential risks to human health, particularly affecting the gut microbiota (GM), intestinal barrier (IB), and blood-brain barrier (BBB). CPF-induced gut dysbiosis compromises the integrity of both the IB and the BBB, leading to increased intestinal permeability, inflammation, and bacterial translocation, all of which may impact neurological health. Although CPF's effects on the GM are documented, limited research explores how these impacts differ in women, particularly during pregnancy. To address this gap, this study investigates CPF's effects using three advanced human in vitro models: the Simulator of the Human Intestinal Microbial Ecosystem (SHIME®) to mimic the gut environment of women of child-bearing age and pregnant women, a Caco-2 model for the IB, and a BBB model to assess CPF's effects and the protective role of the prebiotic inulin. Microbiological analyses of SHIME® supernatants, including bacterial culture and quantification of short-chain fatty acids (SCFAs) and CPF metabolites, were conducted to assess gut composition and pesticide degradation. We also examined the effects of CPF-induced dysbiosis on IB and BBB permeability to FITC-Dextran, focusing on bacterial translocation after 4 h of exposure to CPF-treated SHIME® supernatants. Our results revealed significant intestinal imbalance, marked by an increase in potentially pathogenic bacteria in the GM of both non-pregnant and pregnant women exposed to CPF. This dysbiosis led to a significant shift in SCFAs ratio and increased IB permeability and bacterial translocation across the IB, but not the BBB. Notably, inulin supplementation restored GM balance and prevented bacterial translocation, highlighting its potential as a preventive measure against CPF-induced dysbiosis. This study enhances our understanding of the health risks associated with CPF exposure in women, with implications for maternal and fetal health, and underscores the importance of considering physiological states such as pregnancy in toxicological research.

Gut-brain axis and brain health: modulating neuroinflammation, cognitive decline, and neurodegeneration

The microbiota-gut-brain axis is a pivotal medium of crosstalk between the central nervous system (CNS) and the gastrointestinal tract. It is an intricate network of synergistic molecular pathways that exert their effects far beyond their local vicinity and even affect the systemic functioning of the body. The current review explores the involvement of the gut-brain axis (GBA) in the functioning of the nervous system, with a special emphasis on the neurodegeneration, cognitive decline, and neuroinflammation that occur in Alzheimer's disease (AD) and Parkinson's disease (PD). Gut-derived microbial metabolites play an important role in facilitating this interaction. We also highlighted the complex interaction between gut-derived metabolites and CNS processes, demonstrating how microbial dysbiosis might result in clinical disorders. Short-chain fatty acids have neuroprotective properties, whereas branched-chain amino acids, trimethylamine-N-oxide (TMAO), and tryptophan derivatives such as indole have negative effects at high concentrations. Furthermore, we cover pharmaceutical and nonpharmacological approaches for restoring the gut microbial balance and promoting neurological health. We further expanded on nutritional therapies and lifestyle changes, such as the Mediterranean diet and exercise. Next, we focused on food-controlling habits such as caloric restriction and intermittent fasting. Moreover, interventional techniques such as prebiotics, probiotics, and pharmacological medications have also been utilized to modify the GBA. Historical microbiome research from early discoveries to recent studies linking gut health to cognitive and emotional well-being has increased our understanding of the GBA.

Mitigating lead-induced osteoporosis: The role of butyrate in gut-bone axis restoration

Lead (Pb) is an environmentally widespread bone toxic pollutant, contributes to the development of osteoporosis. Butyric acid, mainly produced by the fermentation of indigestible dietary fiber by gut microbiota, plays a pivotal role in the maintenance of bone homeostasis. However, the effects of butyric acids on the Pb induced osteoporosis have not yet been elucidated. In this study, our results showed that Pb exposure was negatively related to the abundance of butyric acid, in the Pb-exposed population and Pb-exposed mice. Pb exposure caused gut microbiota disorders, resulting in the decline of butyric acid-producing bacteria, such as Butyrivibrio_crossotus, Clostridium_sp._JN9, and the butyrate-producing enzymes through the acetyl-CoA pathway. Moreover, results from the NHANES data suggested that dietary intake of butyrate was associated with a reduced risk of osteoporosis in lead-burdened populations, particularly among men or participants aged 18-60 years. In addition, butyrate supplementation in mice with chronic Pb exposure improved the bone microarchitectures, repaired intestinal damage, upregulated the proportion of Treg cells. Taken together, these results demonstrated that chronic Pb exposure disturbs the gut-bone axis, which can be restored by butyric acid supplement. Our results suggest that butyrate supplementation is a possible therapeutic strategy for lead-induced bone toxicity.

Roles of Epigenetics and Glial Cells in Drug-Induced Autism Spectrum Disorder

Autism spectrum disorder (ASD) is a neurodevelopmental disorder characterized by severe deficits in social communication and interaction, repetitive movements, abnormal focusing on objects, or activity that can significantly affect the quality of life of the afflicted. Neuronal and glial cells have been implicated. It has a genetic component but can also be triggered by environmental factors or drugs. For example, prenatal exposure to valproic acid or acetaminophen, or ingestion of propionic acid, can increase the risk of ASD. Recently, epigenetic influences on ASD have come to the forefront of investigations on the etiology, prevention, and treatment of this disorder. Epigenetics refers to DNA modifications that alter gene expression without making any changes to the DNA sequence. Although an increasing number of pharmaceuticals and environmental chemicals are being implicated in the etiology of ASD, here, we specifically focus on the molecular influences of the abovementioned chemicals on epigenetic alterations in neuronal and glial cells and their potential connection to ASD. We conclude that a better understanding of these phenomena can lead to more effective interventions in ASD.