Brain cholesterol and Alzheimer's disease: challenges and opportunities in probe and drug development

Exosomes in Regulating miRNAs for Biomarkers of Neurodegenerative Disorders

Exosomal proteins and miRNAs, including α-synuclein, Aβ, tau, CXCL12, miR-24, and miR-23b-3p, are emerging as valuable biomarkers for Parkinson's disease and prenatal diagnostics, with significant potential for personalized therapies. Advances in MRI and chitosan-based drug delivery systems are creating new opportunities for diagnosing and treating neurodegenerative disorders. Exosomes regulate miRNAs and proteins, presenting theranostic potential for Alzheimer's and Huntington's diseases, yet facing delivery and targeting challenges. Exosomal miRNAs, such as miR-1234, miR-5678, and miR-29a, are crucial for the early detection and monitoring of the progression of neurodegenerative diseases. Additionally, novel biomarkers such as SCA27B and FGF14 gene mutations and serum miR-455-3p offer promising noninvasive diagnostic methods for Alzheimer's disease. The expanding role of exosome-derived miRNAs in targeting oncogenes and regulating the cell cycle enhances therapeutic strategies for neurological disorders, opening doors to more personalized and effective disease management.

Peripheral Choroid/RPE/Sclera as a Shared Pathogenic Hub: Multi-Tissue Transcriptomic Profiling Identifies Common Differentially Expressed Genes in Age-Related Macular Degeneration and Alzheimer's Disease

BACKGROUND

Age-related macular degeneration (AMD) and Alzheimer's disease (AD), two prevalent neurodegenerative disorders, share overlapping pathophysiological features yet lack cross-disease therapeutic strategies. This study systematically investigates their parallel genes and shared molecular mechanisms to identify potential therapeutic targets for dry AMD, a condition with limited treatment options.

METHODS

Transcriptomic datasets for AMD (GSE155154) and AD (GSE95587) were retrieved from the GEO database. AMD tissues were stratified into four subgroups: macular retina (MR), macular choroid/RPE/sclera (MCRS), peripheral retina (PR), and peripheral choroid/RPE/sclera (PCRS). Common differentially expressed genes (DEGs) were identified and analyzed via functional enrichment (GO, KEGG), gene set enrichment analysis (GSEA), and protein-protein interaction (PPI) networks. Drug-gene interactions and competing endogenous RNA (ceRNA) networks were constructed to prioritize therapeutic targets. Key hub genes were experimentally validated in a sodium iodate-induced AMD murine model using RT-qPCR.

RESULTS

Comparative analysis revealed 89, 56, 4, and 130 common DEGs between AD and MR, MCRS, PR, and PCRS subgroups, respectively. Neuroactive ligand-receptor interactions were prioritized in MR/MCRS-AD analyses, while extracellular matrix organization emerged as the dominant pathway in PCRS-AD comparisons. GSEA identified conserved the TNFα signaling pathway via NF-κB across both diseases. PCRS exhibited consistent expression trends for shared genes and pathways with AD. Computational screening prioritized seven druggable targets (COL1A1, COL1A2, COL3A1, MMP2, MMP9, VCAN, ITGA5) with dual therapeutic potential, along with a reconstructed circRNA (circRNA_002179)-miRNA (miR-124)-mRNA (VCAN) regulatory axis. Experimental validation in a sodium iodate-induced AMD murine model confirmed region-specific dysregulation: hub genes were significantly downregulated in MCRS but upregulated in PCRS.

CONCLUSIONS

Our study delineates both convergent and divergent molecular landscapes of AMD and AD, with PCRS emerging as a critical locus for shared pathophysiology. These findings bridge a critical gap in understanding AMD-AD comorbidity, offering actionable strategies for targeted drug development.

MicroRNA signature of lymphoblasts from amyotrophic lateral sclerosis patients as potential clinical biomarkers

MicroRNAs (miRNAs) are a class of small, non-coding RNAs involved in different cellular functions that have emerged as key regulators of neurodegenerative diseases such as amyotrophic lateral sclerosis (ALS). ALS is a fatal disease that lacks of not only effective treatments, but also presents delays in its diagnosis, since reliable clinical biomarkers are unavailable. In recent years, advancements in high-throughput sequencing strategies have led to the identification of novel ALS biomarkers, facilitating earlier diagnosis and assessment of treatment efficacy. Since immortalized lymphocytes obtained from peripheral blood are a suitable model to study pathological features of ALS, we employed these samples with the aim of characterize the dysregulated miRNAs in ALS patients. Next-generation sequencing (NGS) was utilized in order to analyze the expression profiles of miRNAs in immortalized lymphocytes from healthy controls, sporadic ALS (sALS), and familial ALS with mutations in superoxide dismutase 1 (SOD1-ALS). The screening analysis of the NGS data identified a set of dysregulated miRNAs, of which nine candidates were selected for qRT-PCR validation, identifying for the first time the possible importance of hsa-miR-6821-5p as a potential ALS biomarker. Furthermore, the up-regulated miRNAs identified are predicted to have direct or indirect interactions with genes closely related to ALS, such as SIGMAR1, HNRNPA1 and TARDBP. Additionally, by Metascape enrichment analysis, we found the VEGFA/VEGFR2 signaling pathway, previously implicated in neuroprotective effects in ALS, as a candidate pathway for further analyses.

Brain Cytochrome P450: Navigating Neurological Health and Metabolic Regulation

Human cytochrome P450 (CYP) enzymes in the brain represent a crucial frontier in neuroscience, with far-reaching implications for drug detoxification, cellular metabolism, and the progression of neurodegenerative diseases. The brain's complex architecture, composed of interconnected cell types and receptors, drives unique neuronal signaling pathways, modulates enzyme functions, and leads to distinct CYP gene expression and regulation patterns compared to the liver. Despite their relatively low levels of expression, brain CYPs exert significant influence on drug responses, neurotoxin susceptibility, behavior, and neurological disease risk. These enzymes are essential for maintaining brain homeostasis, mediating cholesterol turnover, and synthesizing and metabolizing neurochemicals, neurosteroids, and neurotransmitters. Moreover, they are key participants in oxidative stress responses, neuroprotection, and the regulation of inflammation. In addition to their roles in metabolizing psychotropic drugs, substances of abuse, and endogenous compounds, brain CYPs impact drug efficacy, safety, and resistance, underscoring their importance beyond traditional drug metabolism. Their involvement in critical physiological processes also links them to neuroprotection, with significant implications for the onset and progression of neurodegenerative diseases. Understanding the roles of cerebral CYP enzymes is vital for advancing neuroprotective strategies, personalizing treatments for brain disorders, and developing CNS-targeting therapeutics. This review explores the emerging roles of CYP enzymes, particularly those within the CYP1-3 and CYP46 families, highlighting their functional diversity and the pathological consequences of their dysregulation on neurological health. It also examines the potential of cerebral CYP-based biomarkers to improve the diagnosis and treatment of neurodegenerative disorders, offering new avenues for therapeutic innovation.

Lipidome disruption in Alzheimer's disease brain: detection, pathological mechanisms, and therapeutic implications

Alzheimer's disease (AD) is among the most devastating neurodegenerative disorders with limited treatment options. Emerging evidence points to the involvement of lipid dysregulation in the development of AD. Nevertheless, the precise lipidomic landscape and the mechanistic roles of lipids in disease pathology remain poorly understood. This review aims to highlight the significance of lipidomics and lipid-targeting approaches in the diagnosis and treatment of AD. We summarized the connection between lipid dysregulation in the human brain and AD at both genetic and lipid species levels. We briefly introduced lipidomics technologies and discussed potential challenges and areas of future advancements in the lipidomics field for AD research. To elucidate the central role of lipids in converging multiple pathological aspects of AD, we reviewed the current knowledge on the interplay between lipids and major AD features, including amyloid beta, tau, and neuroinflammation. Finally, we assessed the progresses and obstacles in lipid-based therapeutics and proposed potential strategies for leveraging lipidomics in the treatment of AD.

Association between calculated remnant cholesterol levels and incident risks of Alzheimer's disease among elderly patients with type 2 diabetes: a real-world study

Objective

Alzheimer's disease (AD) is a leading cause of dementia, with a rising global burden. Remnant cholesterol (RC), a component of triglyceride-rich lipoproteins, has been implicated in cardiovascular diseases and metabolic disorders, but its role in AD remains unclear. This study investigated the association between RC levels and the risk of AD among elderly patients with type 2 diabetes (T2D) in a real-world clinical setting.

Methods

We conducted a retrospective cohort study using electronic medical records from Gongli Hospital of Shanghai Pudong New Area, covering the period from 2013 to 2023. The study included 15,364 elderly patients aged 65-80 years with T2D. RC levels were calculated using the equation. The primary outcome was the diagnosis of AD, validated by neurologists using ICD-10-CM code G30. Cox proportional hazards models were employed to estimate hazard ratios (HRs) for AD across quartiles of RC levels, adjusting for potential confounders.

Results

Over a mean follow-up of 3.69 ± 1.33 years, 312 new cases of AD were identified. A U-shaped relationship was observed between RC levels and AD risk, with the lowest risk associated with RC levels between 0.58-0.64 mmol/L. Both lower (<0.52 mmol/L) and higher (≥0.77 mmol/L) RC levels were linked to increased AD risk. Compared to the reference group (Q2: 0.52-0.64 mmol/L), the adjusted HRs (95% CI) for the lowest and highest quartiles were 1.891 (1.368-2.613) and 1.891 (1.363-2.622), respectively. Each 1 mmol/L increase in RC was associated with a 3.47-fold higher risk of AD (HR=4.474, 95% CI 2.330-8.592).

Conclusion

RC levels may serve as a predictive biomarker for AD risk, with both extremes posing a higher risk. Future studies should explore the mechanistic pathways and potential interventions targeting RC to prevent AD in high-risk populations.

Do Statins Affect Cognitive Health? A Narrative Review and Critical Analysis of the Evidence

PURPOSE OF REVIEW

Statins are the first-line treatment for hypercholesterolemia and play a key role in the prevention of cardiovascular disease (CVD). Current studies report mixed effects of statins on cognitive health, including harmful, neutral, and protective outcomes. However, these ongoing controversies about the potential cognitive adverse effects of statins may compromise their use in CVD prevention. Several factors may influence how statins affect cognition, including the unique cholesterol homeostasis in the brain, the limited permeability of the blood-brain barrier to lipoproteins, and the varying lipophilicity of different statins. This review examines the evidence linking statins to cognitive function and considers the effect of different dosages and treatment durations.

RECENT FINDINGS

Earlier studies suggested cognitive disturbances with statins, but recent evidence does not strongly support a link between statins and cognitive impairment. In fact, observational studies suggest potential neuroprotective benefits, though biases like selection bias, confounding and reverse causation limit definitive conclusions. Two large randomized controlled trials, STAREE and PREVENTABLE, are underway, and their results are expected to address some of these gaps in the literature. Due to insufficient evidence in the current literature, well-designed randomized controlled trials are needed for a better understanding of statins' effects on cognition. More data is needed regarding statin type, dose intensity, and treatment duration, which may affect cognitive outcomes. Future studies are also needed to examine how statins may affect cognition in specific high-risk groups, such as individuals with mild cognitive impairment, diabetes, cardiovascular disease, or chronic kidney disease.

Exposure to lipid mixture induces intracellular lipid droplet formation and impairs mitochondrial functions in astrocytes

Astrocytes, the predominant glial cells in the central nervous system (CNS), play diverse roles including metabolic support for neurons, provision of neurotrophic factors, facilitation of synaptic neurotransmitter uptake, regulation of ion balance, and involvement in synaptic formation. The accumulation of lipids has been noted in various neurological conditions, yet the response of astrocytes to lipid-rich environments remains unclear. In this study, primary astrocytes isolated from the neonatal rat cortex were exposed to a lipid mixture (LM) comprising cholesterol and various fatty acids to explore their reaction. Our results showed that astrocyte viability remained unchanged following 24 h of 5% or 10% LM treatment. However, exposure to LM for 96 h resulted in reduced cell viability. In addition, LM treatment led to the accumulation of lipid droplets (LDs) in astrocytes, with LD size increasing over prolonged exposure periods. Following 24 h of LM treatment and then 48 h in fresh medium, a significant reduction in intracellular LD size was observed in cultures treated with 5% LM, while no change occurred in cultures exposed to 10% LM. Yet, exposure to 10% LM for 24 h significantly increased the expression of the cholesterol efflux regulatory protein/ATP-binding cassette transporter (ABCA1) gene, responsible for intracellular cholesterol efflux, resulting in reduced cholesterol content within astrocytes. Moreover, LM exposure led to decreased mitochondrial membrane potential (MMP) and increased levels of mature apoptosis-inducing factor (AIF). The smaller LDs were observed to co-localize with microtubule-associated protein 1A/1 B light chain 3 B (LC3) and lysosomal-associated membrane protein-1 (LAMP-1) in LM-treated astrocytes, coinciding with lysosomal acidification. These results indicate that the continuous buildup of LDs in astrocytes residing in lipid-enriched environments may be attributed to disruptions caused by LM in mitochondrial and lysosomal functions. Such disruptions could potentially impede the supportive role of astrocytes in neuronal function.

Recent advances in Alzheimer's disease: Mechanisms, clinical trials and new drug development strategies

Alzheimer's disease (AD) stands as the predominant form of dementia, presenting significant and escalating global challenges. Its etiology is intricate and diverse, stemming from a combination of factors such as aging, genetics, and environment. Our current understanding of AD pathologies involves various hypotheses, such as the cholinergic, amyloid, tau protein, inflammatory, oxidative stress, metal ion, glutamate excitotoxicity, microbiota-gut-brain axis, and abnormal autophagy. Nonetheless, unraveling the interplay among these pathological aspects and pinpointing the primary initiators of AD require further elucidation and validation. In the past decades, most clinical drugs have been discontinued due to limited effectiveness or adverse effects. Presently, available drugs primarily offer symptomatic relief and often accompanied by undesirable side effects. However, recent approvals of aducanumab (1) and lecanemab (2) by the Food and Drug Administration (FDA) present the potential in disrease-modifying effects. Nevertheless, the long-term efficacy and safety of these drugs need further validation. Consequently, the quest for safer and more effective AD drugs persists as a formidable and pressing task. This review discusses the current understanding of AD pathogenesis, advances in diagnostic biomarkers, the latest updates of clinical trials, and emerging technologies for AD drug development. We highlight recent progress in the discovery of selective inhibitors, dual-target inhibitors, allosteric modulators, covalent inhibitors, proteolysis-targeting chimeras (PROTACs), and protein-protein interaction (PPI) modulators. Our goal is to provide insights into the prospective development and clinical application of novel AD drugs.

Lipids and α-Synuclein: adding further variables to the equation

Aggregation of alpha-Synuclein (αSyn) has been connected to several neurodegenerative diseases, such as Parkinson's disease (PD), dementia with Lewy Bodies (DLB), and multiple system atrophy (MSA), that are collected under the umbrella term synucleinopathies. The membrane binding abilities of αSyn to negatively charged phospholipids have been well described and are connected to putative physiological functions of αSyn. Consequently, αSyn-related neurodegeneration has been increasingly connected to changes in lipid metabolism and membrane lipid composition. Indeed, αSyn aggregation has been shown to be triggered by the presence of membranes in vitro, and some genetic risk factors for PD and DLB are associated with genes coding for proteins directly involved in lipid metabolism. At the same time, αSyn aggregation itself can cause alterations of cellular lipid composition and brain samples of patients also show altered lipid compositions. Thus, it is likely that there is a reciprocal influence between cellular lipid composition and αSyn aggregation, which can be further affected by environmental or genetic factors and ageing. Little is known about lipid changes during physiological ageing and regional differences of the lipid composition of the aged brain. In this review, we aim to summarise our current understanding of lipid changes in connection to αSyn and discuss open questions that need to be answered to further our knowledge of αSyn related neurodegeneration.

Investigating cocaine- and abstinence-induced effects on astrocyte gene expression in the nucleus accumbens

In recent years, astrocytes have been increasingly implicated in cellular mechanisms of substance use disorders (SUD). Astrocytes are structurally altered following exposure to drugs of abuse; specifically, astrocytes within the nucleus accumbens (NAc) exhibit significantly decreased surface area, volume, and synaptic colocalization after operant self-administration of cocaine and extinction or protracted abstinence (45 days). However, the mechanisms that elicit these morphological modifications are unknown. The current study aims to elucidate the molecular modifications that lead to observed astrocyte structural changes in rats across cocaine abstinence using astrocyte-specific RiboTag and RNA-seq, as an unbiased, comprehensive approach to identify genes whose transcription or translation change within NAc astrocytes following cocaine self-administration and extended abstinence. Using this method, our data reveal cellular processes including cholesterol biosynthesis that are altered specifically by cocaine self-administration and abstinence, suggesting that astrocyte involvement in these processes is changed in cocaine-abstinent rats. Overall, the results of this study provide insight into astrocyte functional adaptations that occur due to cocaine exposure or during cocaine withdrawal, which may pinpoint further mechanisms that contribute to cocaine-seeking behavior.

Navigating the metabolic maze: anomalies in fatty acid and cholesterol processes in Alzheimer's astrocytes

Alzheimer's disease (AD) is the most common cause of dementia, and its underlying mechanisms have been a subject of great interest. The mainstream theory of AD pathology suggests that the disease is primarily associated with tau protein and amyloid-beta (Aβ). However, an increasing body of research has revealed that abnormalities in lipid metabolism may be an important event throughout the pathophysiology of AD. Astrocytes, as important members of the lipid metabolism network in the brain, play a significant role in this event. The study of abnormal lipid metabolism in astrocytes provides a new perspective for understanding the pathogenesis of AD. This review focuses on the abnormal metabolism of fatty acids (FAs) and cholesterol in astrocytes in AD, and discusses it from three perspectives: lipid uptake, intracellular breakdown or synthesis metabolism, and efflux transport. We found that, despite the accumulation of their own fatty acids, astrocytes cannot efficiently uptake fatty acids from neurons, leading to fatty acid accumulation within neurons and resulting in lipotoxicity. In terms of cholesterol metabolism, astrocytes exhibit a decrease in endogenous synthesis due to the accumulation of exogenous cholesterol. Through a thorough investigation of these metabolic abnormalities, we can provide new insights for future therapeutic strategies by literature review to navigate this complex metabolic maze and bring hope to patients with Alzheimer's disease.