Microbiota-derived lysophosphatidylcholine alleviates Alzheimer's disease pathology via suppressing ferroptosis

Causal relationship between gut microbiota, lipids, and neuropsychiatric disorders: A Mendelian randomization mediation study

BACKGROUND

Numerous studies have shown an interconnection between the gut microbiota and the brain via the "gut-brain" axis. However, the causal relationships between gut microbiota, lipids, and neuropsychiatric disorders remain unclear. This study aimed to analyze potential associations among gut microbiota, lipids, and neuropsychiatric disorders-including AD, PD, ALS, MS, SCZ, MDD, and BD-using summary data from large-scale GWAS.

METHODS

Bidirectional Mendelian randomization (MR) with inverse variance weighting (IVW) was the primary method. Supplementary analyses included sensitivity analyses, Steiger tests, and Bayesian weighted MR (BWMR). Mediation analyses used two-step MR (TSMR) and multivariable MR (MVMR).

RESULTS

The analyses revealed 51 positive correlations (risk factors) (β > 0, P < 0.05) and 47 negative correlations (protective factors) (β < 0, P < 0.05) between gut microbiota and neuropsychiatric disorders. In addition, 35 positive correlations (β > 0, P < 0.05) and 22 negative correlations (β < 0, P < 0.05) between lipids and neuropsychiatric disorders were observed. Assessment of reverse causality with the seven neuropsychiatric disorders as exposures and the identified gut microbiota and lipids as outcomes revealed no evidence of reverse causality (P > 0.05). Mediation analysis indicated that the effect of the species Bacteroides plebeius on MDD is partially mediated through the regulation of phosphatidylcholine (16:0_20:4) levels (mediation proportion = 10.9 % [95 % CI = 0.0110-0.2073]).

CONCLUSION

This study provides evidence of a causal relationship between gut microbiota and neuropsychiatric disorders, suggesting lipids as mediators. These findings offer new insights into the mechanisms by which gut microbiota may influence neuropsychiatric disorders.

Compositional and functional gut microbiota alterations in mild cognitive impairment: links to Alzheimer's disease pathology

BACKGROUND

Emerging evidence highlights the bidirectional communication between the gut microbiota and the brain, suggesting a potential role for gut dysbiosis in Alzheimer's disease (AD) pathology and cognitive decline. Existing literature on gut microbiota lacks species-level insights. This study investigates gut microbiota alterations in mild cognitive impairment (MCI), focusing on their association with comprehensive AD biomarkers, including amyloid burden, tau pathology, neurodegeneration, and cognitive performance.

METHODS

We analyzed fecal samples from 119 individuals with MCI and 320 cognitively normal controls enrolled in the Taiwan Precision Medicine Initiative on Cognitive Impairment and Dementia cohort. Shotgun metagenomic sequencing was conducted with taxonomic profiling using MetaPhlAn4. Amyloid burden and plasma pTau181 were quantified via PET imaging and Simoa assays, respectively, while APOE genotyping was performed using TaqMan assays. Microbial diversity, differential abundance analysis, and correlation mapping with neuropsychological and neuroimaging measures were conducted to identify gut microbiota species signatures associated with MCI and AD biomarkers.

RESULTS

We identified 59 key microbial species linked to MCI and AD biomarkers. Notably, species within the same genera, such as Bacteroides and Ruminococcus, showed opposing effects, while Akkermansia muciniphila correlated with reduced amyloid burden, suggesting a protective role. Functional profiling revealed microbial pathways contributing to energy metabolism and neuroinflammation, mediating the relationship between gut microbes and brain health. Co-occurrence network analyses demonstrated complex microbial interactions, indicating that the collective influence of gut microbiota on neurodegeneration.

CONCLUSIONS

Our findings challenge genus-level microbiome analyses, revealing species-specific modulators of AD pathology. This study highlights gut microbial activity as a potential therapeutic target to mitigate cognitive decline and neurodegeneration.

The Role of G Protein-Coupled Receptors in the Regulation of Orthopaedic Diseases by Gut Microbiota

Exercise and diet modulate the gut microbiota, which is involved in the regulation of orthopaedic diseases and synthesises a wide range of metabolites that modulate cellular function and play an important role in bone development, remodelling and disease. G protein-coupled receptors (GPCRs), the largest family of transmembrane receptors in the human body, interact with gut microbial metabolites to regulate relevant pathological processes. This paper provides a review of different dietary and exercise effects on the pathogenic gut microbiota and their metabolites associated with GPCRs in orthopaedic diseases. RESULTS: Generally, metabolites produced by gut microbiota contribute to the maintenance of bone health by activating the corresponding GPCRs, which are involved in bone metabolism, regulation of immune response, and maintenance of gut flora homeostasis. Exercise and diet can influence gut microbiota, and an imbalance in gut microbiota homeostasis can trigger a series of adverse immune and metabolic responses by affecting GPCR function, ultimately leading to the onset and progression of various orthopaedic diseases. Understanding these relationships is crucial for elucidating the pathogenesis of orthopaedic diseases and developing personalised probiotic-based therapeutic strategies. In the future, we should further explore how to prevent and treat orthopaedic diseases through GPCR-based modulation of gut microbes and their interactions. The development of substances that precisely modulate gut microbes through different exercises and diets will provide more effective interventions to improve bone health in patients.

Tea Polyphenols Mitigate Radiation-Induced Ferroptosis and Intestinal Injury by Targeting the Nrf2/HO-1/GPX4 Signaling Pathway

Radiation-induced intestinal injury (RIII) is a significant concern for cancer patients receiving radiation therapy, as it can lead to complications such as radiation enteropathy. Presently, there are limited options for preventing or treating RIII. Tea polyphenols (TP), found in tea, provide various health benefits, but their antiradiation mechanisms are not fully understood. C57BL/6 mice pre-treated with TP for five days showed a significant improvement in survival rates after being exposed to 10 Gy of 60Co radiation. In the same way, abdominal exposure to 15 Gy of 60Co radiation effectively mitigated radiation-induced colon shortening, damage to intestinal tissues, oxidative stress, the release of inflammatory factors, and disruptions in intestinal microbial balance. In addition, TP treatment lowered the elevation of reactive oxygen species (ROS), iron imbalance, mitochondrial damage, and ferroptosis in IEC-6 cells post-irradiation. Utilizing network pharmacology, molecular docking, and affinity testing, we identified that TP has the capability to target the Nrf2/HO-1/GPX4 signaling pathway, while EGCG, a principal constituent of TP, interacts with HSP90 and mitigates radiation-induced ferroptosis. These findings suggest that TP may serve as a promising therapeutic agent to alleviate radiation-induced intestinal injury (RII).

Enhanced Microglial Engulfment of Dopaminergic Synapses Induces Parkinson's Disease-Related Executive Dysfunction in an Acute LPC Infusion Targeting the mPFC

The dysfunction of the dopaminergic projection from the ventral tegmental area (VTA) to the medial prefrontal cortex (mPFC) is believed to play a key role in the pathophysiology of Parkinson's disease (PD) accompanied by executive dysfunction (EDF). In this study, we identified an abnormal increase in lysophosphatidylcholine (LPC) levels in PD patients, which closely correlates with the severity of cognitive impairment. LPC disrupts the miR-2885/TDP-43 signaling pathway in microglia, driving dopaminergic presynaptic engulfment. In LPC-exposed mice, microglial activation via miR-2885/TDP-43/p65 signaling led to inflammatory cytokine and complement release, marking dopaminergic synapses for phagocytosis with a "PS/C1q" signal. Following the inhibition of LPC-induced microglial activation through chemogenetic methods, we observed a significant reduction in the phagocytosis of dopaminergic synapses, resulting in improved executive function. The miR-2885 disrupted LPC-induced dopaminergic phagocytosis and alleviated EDF. Furthermore, the accumulation of excessive TDP-43 due to the loss of miR-2885 promoted the engulfment of dopaminergic synapses by facilitating the entry of p65 into the nucleus. Inhibiting TDP-43 levels effectively mitigated LPC-induced EDF. Additionally, supplementing dopamine receptor agonists enhanced the excitability of regional glutamatergic neurons, leading to improved executive function. In summary, LPC exposure in the mPFC impairs microglial regulation, leading to dopaminergic synaptic loss and underactivity of glutamatergic neurons. These changes drive the development of executive dysfunction in PD.

Poria cocos Polysaccharide Reshapes Gut Microbiota to Regulate Short-Chain Fatty Acids and Alleviate Neuroinflammation-Related Cognitive Impairment in Alzheimer's Disease

Evidence indicates that Poria cocos polysaccharide (PCP) improves cognitive impairment in Alzheimer's disease (AD); however, its underlying mechanism, particularly its relationship with the gut microbiota, remains unclear. In the current study, we aimed to investigate the mechanism of PCP in improving cognitive impairment in AD. The results demonstrated that PCP markedly enhanced cognitive function and mitigated AD-related pathological alterations in 3 × Tg-AD mice. PCP treatment reversed the age-dependent gut microbiota dysbiosis in 3 × Tg-AD mice by 16S rDNA sequencing. The contents of propanoic acid, butanoic acid and isohexanoic acid were increased by short-chain fatty acid determination. In addition, PCP could restore both the intestinal barrier and the blood-brain barrier, as demonstrated by immunofluorescence staining of tight junction proteins. Furthermore, PCP alleviated systemic inflammation and neuroinflammation, as evidenced by reduced LPS levels in circulation and decreased IL-6 levels in the brain, likely by inhibiting the TLR4/NF-κB signaling pathway. In conclusion, PCP can reshape gut microbiota to regulate short-chain fatty acids and alleviate neuroinflammation-related cognitive impairment in AD mice.

Ferroptosis and Iron Homeostasis: Molecular Mechanisms and Neurodegenerative Disease Implications

Iron dysregulation has emerged as a pivotal factor in neurodegenerative pathologies, especially through its capacity to promote ferroptosis, a unique form of regulated cell death driven by iron-catalyzed lipid peroxidation. This review synthesizes current evidence on the molecular underpinnings of ferroptosis, focusing on how disruptions in iron homeostasis interact with key antioxidant defenses, such as the system Xc--glutathione-GPX4 axis, to tip neurons toward lethal oxidative damage. Building on these mechanistic foundations, we explore how ferroptosis intersects with hallmark pathologies in Alzheimer's disease (AD) and Parkinson's disease (PD) and examine how iron accumulation in vulnerable brain regions may fuel disease-specific protein aggregation and neurodegeneration. We further surveyed the distinct components of ferroptosis, highlighting the role of lipid peroxidation enzymes, mitochondrial dysfunction, and recently discovered parallel pathways that either exacerbate or mitigate neuronal death. Finally, we discuss how these insights open new avenues for neuroprotective strategies, including iron chelation and lipid peroxidation inhibitors. By highlighting open questions, this review seeks to clarify the current state of knowledge and proposes directions to harness ferroptosis modulation for disease intervention.

Lysophosphatidylcholine promoting α-Synuclein aggregation in Parkinson's disease: disrupting GCase glycosylation and lysosomal α-Synuclein degradation

In Parkinson's Disease (PD), elevated serum lysophosphatidylcholine (LPC) levels correlate with disease progression. However, the mechanisms by which abnormal LPC elevation contributes to PD-related neurotoxicity remain poorly understood. This study aims to investigate the pathogenic role of LPC in dopaminergic neuronal damage and elucidates its underlying mechanisms. Our results showed LPC induces α-synuclein aggregation, exacerbating cognitive dysfunction. LPC activates Cleaved-Caspase3 via the orphan receptor GPR35-ERK signaling pathway, inhibits GRASP65 expression, and disrupts the polarized structure of the Golgi apparatus. This disruption impairs glycosylation and function of glucocerebrosidase (GCase), preventing its transport to lysosomes and leading to glucosylceramide (GlcCer) accumulation, a scaffold for α-synuclein aggregation. LPC also disrupts the autophagolysosomal pathway and lysosomal acidification, exacerbating toxic α-synuclein accumulation. Restoring GCase glycosylation, limiting GlcCer synthesis, or blocking ERK signaling mitigates these effects. This study highlights LPC's role in promoting α-synuclein aggregation and autophagolysosomal dysfunction, advancing our understanding of PD pathology.

Radiation-Induced Brain Injury: Mechanistic Insights and the Promise of Gut-Brain Axis Therapies

Radiation therapy is widely recognized as an efficacious modality for treating neoplasms located within the craniofacial region. Nevertheless, this approach is not devoid of risks, predominantly concerning potential harm to the neural structures. Adverse effects may encompass focal cerebral necrosis, cognitive function compromise, cerebrovascular pathology, spinal cord injury, and detriment to the neural fibers constituting the brachial plexus. With increasing survival rates among oncology patients, evaluating post-treatment quality of life has become crucial in assessing the benefits of radiation therapy. Consequently, it is imperative to investigate therapeutic strategies to mitigate cerebral complications from radiation exposure. Current management of radiation-induced cerebral damage involves corticosteroids and bevacizumab, with preclinical research on antioxidants and thalidomide. Despite these efforts, an optimal treatment remains elusive. Recent studies suggest the gut microbiota's involvement in neurologic pathologies. This review aims to discuss the causes and existing treatments for radiation-induced cerebral injury and explore gut microbiota modulation as a potential therapeutic strategy.

Targeting Ferroptosis in Parkinson's Disease: Mechanisms and Emerging Therapeutic Strategies

Parkinson's disease (PD) is a common neurodegenerative disorder characterized by the loss of dopaminergic neurons in the substantia nigra and the accumulation of α-synuclein in the brain. Ferroptosis, a recently identified form of regulated cell death, is critical in PD pathogenesis due to its association with iron deposition, overproduction of reactive oxygen species, iron-dependent lipid peroxidation and impaired lipid peroxidation clearance. This cell death mechanism is closely linked to several pathogenic processes in PD, including α-synuclein aggregation, oxidative stress, mitochondrial dysfunction, microglia-induced neuroinflammation, and neuromelanin accumulation. Given the significant role of ferroptosis in these mechanisms, there is increasing interest in targeting ferroptosis for PD treatment. Several drugs have shown potential in alleviating PD symptoms by inhibiting ferroptosis. This review aims to consolidate current knowledge on ferroptosis in PD and assess the therapeutic potential of anti-ferroptosis drugs, highlighting promising directions for future research and clinical applications.