Cholesterol Metabolism in Aging and Age-Related Disorders

Silencing of the plant-derived horizontally transferred gene BtSC5DL effectively controls Bemisia tabaci MED

BACKGROUND

The whitefly Bemisia tabaci is a notorious agricultural pest known for its ability to cause significant crop damage through direct feeding and virus transmission. Its remarkable adaptability and reproductive capacity are linked to its ability to acquire and integrate horizontally transferred genes (HTGs) into its genome. These HTGs increase the physiological and metabolic capacities of this pest, including cholesterol synthesis, which is critical for its survival and reproductive success. Among these genes, we identified a plant-derived B. tabaci Δ7-sterol C5-desaturase-like gene (BtSC5DL), which plays a pivotal role in B. tabaci cholesterol metabolism and reproductive biology.

RESULTS

In this study, we cloned and identified the BtSC5DL gene from B. tabaci Mediterranean (MED). Bioinformatics and molecular analyses revealed that BtSC5DL was transferred from plants to B. tabaci millions of years ago and is now stably expressed in this species. Silencing BtSC5DL through dsRNA feeding resulted in significant reductions in egg production and cholesterol content in B. tabaci MED. Furthermore, virus-induced gene silencing (VIGS) experiments confirmed that long-term suppression of BtSC5DL had a notable ability to control whitefly populations.

CONCLUSION

Our results demonstrate the crucial role of BtSC5DL in cholesterol biosynthesis in B. tabaci MED and suggest that the acquisition of this gene significantly enhances the reproductive capacity of this species. These findings provide a theoretical basis for the development of RNA interference (RNAi)-based pest control strategies targeting BtSC5DL, offering a potential new approach for the effective management of whitefly populations in agricultural settings. © 2025 Society of Chemical Industry.

Cordycepin extends the longevity of Caenorhabditis elegans via antioxidation and regulation of fatty acid metabolism

Aging can cause age-related diseases such as cancer, cardiovascular and neurodegenerative diseases. Cordycepin exerts anti-oxidation, anti-inflammatory and neuroprotective effects. However, the anti-aging effect of cordycepin is still unclear. This study aimed to investigate the anti-aging effect of cordycepin and unravel the underlying mechanism. Cordycepin prolonged the lifespan of C. elegans under normal and heat stress conditions, without effects on the normal growth and reproduction of C. elegans. Cordycepin also improved the locomotion ability, inhibited the deposition of aging pigment lipofuscin and alleviated the oxidative stress damage by decreasing the excessive accumulation of ROS and raising the antioxidant enzyme activities in C. elegans. The metabolomics study showed that cordycepin changed 19 metabolites including citric acid, linoleic acid, oleic acid, glutamic acid, pyruvic acid and so on. Transcriptomics study revealed that cordycepin up-regulated the gene expression of acox-1.2, acox-1.3, acox-1.4, acs-1, acs-15, acdh-1, acdh-4 and acdh-8 in C. elegans, suggesting that cordycepin prolonged its lifespan via regulating fatty acid degradation, fatty acid metabolism and so on. In summary, the current study demonstrated that cordycepin exerted the anti-aging effect on C. elegans by improving the antioxidant system and regulating the genes involved in fatty acid metabolism to inhibit the accumulation of linoleic acid and oleic acid. Therefore, cordycepin might be a promising agent for aging and age-related diseases.

Cholesterol-modifying strategies for Alzheimer disease: promise or fallacy?

INTRODUCTION

As the world population ages, Alzheimer disease (AD) prevalence increases. However, understanding of AD etiology continues to evolve, and the pathophysiological processes involved are only partially elucidated. One compound suspected to play a role in the development and progression of AD is cholesterol. Several lines of evidence support this connection, yet it remains unclear whether cholesterol-modifying strategies have potential applications in the clinical management of AD.

AREAS COVERED

A deep literature search using PubMed was performed to prepare this narrative review. The literature search, performed in early 2024, was inclusive of literature from 1990 to 2024. After providing an overview of cholesterol metabolism, this study summarizes key preclinical studies that have investigated cholesterol-modifying therapies in laboratory models of AD. It also summarizes past and current clinical trials testing specific targets modulated by anti-cholesterol therapies in AD patients.

EXPERT OPINION

Based on current epidemiological and mechanistic studies, cholesterol likely plays a role in AD etiology. The use of cholesterol-modifying therapies could be a promising treatment approach if administered at presymptomatic to early AD phases, but it is unlikely to be efficient in mild, moderate, and late AD stages. Several recommendations are provided for hypercholesterolemia management in AD patients.

Neuroinflammation in Alzheimer disease

Increasing evidence points to a pivotal role of immune processes in the pathogenesis of Alzheimer disease, which is the most prevalent neurodegenerative and dementia-causing disease of our time. Multiple lines of information provided by experimental, epidemiological, neuropathological and genetic studies suggest a pathological role for innate and adaptive immune activation in this disease. Here, we review the cell types and pathological mechanisms involved in disease development as well as the influence of genetics and lifestyle factors. Given the decade-long preclinical stage of Alzheimer disease, these mechanisms and their interactions are driving forces behind the spread and progression of the disease. The identification of treatment opportunities will require a precise understanding of the cells and mechanisms involved as well as a clear definition of their temporal and topographical nature. We will also discuss new therapeutic strategies for targeting neuroinflammation, which are now entering the clinic and showing promise for patients.

The roles of enhancer, especially super-enhancer-driven genes in tumor metabolism and immunity

Abnormal metabolism is a characteristic of malignant tumors. Numerous factors play roles in the regulation of tumor metabolism. As epigenetic regulators, enhancers, especially the super-enhancers (SEs), serve as platforms for transcription factors that regulate the expression of metabolism-related enzymes or transporters at the gene level. In this study, we review the effects of enhancer/ SE-driven genes on tumor metabolism and immunity. Enhancers/SEs play regulatory roles in glucose metabolism (glycolysis, gluconeogenesis, tricarboxylic acid (TCA) cycle, pyruvate, and pentose phosphate pathway, lipid metabolism (cholesterol, fatty acid, phosphatide, and sphingolipid), and amino acid metabolism (glutamine, tryptophan, arginine, and cystine). By regulating tumor metabolism, enhancers and SEs can reprogram tumor microenvironment, especially the status of various immune cells. Therefore, interfering enhancers/SEs that regulate the tumor metabolism is likely to enhance the effectiveness of immunotherapy.

Cholesterol´s role in membrane organization and nicotinic acetylcholine receptor function: Implications for aging and Alzheimer's disease

Biological membranes are complex entities composed of various molecules exhibiting lateral and transbilayer lipid asymmetries, along with a selective spatial distribution of different membrane proteins. This dynamic orchestration is crucial for proper physiological functions, undergoes changes with aging, and is disturbed in several neurological disorders. In this review, we analyze the impact of disruption in this equilibrium on physiological aging and the onset of pathological conditions. Alzheimer´s disease (AD) is a multifactorial neurodegenerative disorder in the elderly, characterized by the increased presence of the Aβ peptide, which supports the amyloid hypothesis of the disease. However, AD also involves a progressive loss of cholinergic innervation, leading to the cholinergic hypothesis of the disease. Nicotinic acetylcholine receptors (nAChRs) are transmembrane proteins, and Aβ peptides, their oligomeric and fibrillar species, which increase in hydrophobicity as they develop, interact with membranes. Therefore, a membrane hypothesis of the disease emerges as a bridge between the other two. Here, we discuss the impact of the membrane environment, through direct or indirect mechanisms, on cholinergic signaling and Aβ formation and subsequent incorporation into the membrane, with a special focus on the crucial role of cholesterol in these processes.

Regulation of CNS Lipids by Protease Activated Receptor 1

Disruptions in the metabolism of cholesterol and other lipids are strongly implicated in the pathogenesis of neurological disease. The CNS is highly enriched in cholesterol, which is primarily synthesized de novo. Cholesterol synthesis is also rate limiting for myelin regeneration. Given that knockout of the thrombin receptor (Protease Activated Receptor 1 (PAR1)) accelerates myelin regeneration, here we sought to determine the potential regulatory actions of PAR1 in CNS cholesterol and lipid metabolism in the intact adult CNS and during myelin regeneration. We present quantitative PCR and RNAseq evidence from murine spinal cords at the peak of myelination and in adulthood showing PAR1 knockout is associated with increased gene expression for cholesterol biosynthesis (Hmgcs1, Hmgcr, Sqle, and Dhcr7), lipid transport (ApoE, Abca1, and Ldlr), and intracellular processing (Lcat, Npc1, and Npc2) at one or more time points examined. An upregulation of genes involved in the synthesis of other lipids enriched in the myelin membrane, specifically Fa2h, Ugt8a, and Gal3st1, was also observed in PAR1 knockouts. Transcription factors essential for lipid and cholesterol production (Srebf1 and Srebf2) were also increased in PAR1 knockout spinal cords at the postnatal day 21 peak of myelination and at day 45. GC-MS and LC-MS quantification of lipids demonstrated coordinate increases in the abundance of select cholesterol and lipid species in the spinal cords of PAR1 knockout mice, including enrichment of esterified cholesterol, together with sphingomyelins and sphingolipids. Co-localization of the SREBP1 and SREBP2 transcription factors, as well as HMGCS1, a rate-limiting enzyme in cholesterol biosynthesis, to glia during remyelination post-lysolecithin or cuprizone-mediated demyelination showed a prominent regulatory role for PAR1 in Olig2+ oligodendrocytes. PAR1 knockouts also demonstrated elevated levels of SREBP2 in more mature GST3+ oligodendrocytes and SREBP1 in GFAP+ astrocytes during remyelination post-lysolecithin. These findings demonstrate novel roles for PAR1 as a regulator of CNS cholesterol and lipid metabolism and its potential as a therapeutic target to increase cholesterol availability to improve myelin regeneration.

ABCA6 Regulates Chondrogenesis and Inhibits Joint Degeneration via Orchestrated Cholesterol Efflux and Cellular Senescence

Patellar dysplasia (PD) can cause patellar dislocation and subsequent osteoarthritis (OA) development. Herein, a novel ABCA6 mutation contributing to a four-generation family with familiar patellar dysplasia (FPD) is identified. In this study, whole exome sequencing (WES) and genetic linkage analysis across a four-generation lineage presenting with six cases of FPD are conducted. A disease-causing mutation in ABCA6 is identified for FPD. Further analyses reveal a consistent correlation between ABCA6 expression downregulation and PD occurrence, chondrocyte degeneration, and OA onset. Moreover, ABCA6-KO mice demonstrate severe knee joint degeneration and accelerated OA progression. Besides, synovial mesenchymal stem cells (SMSCs) are extracted from WT, ABCA6-/+, and ABCA6-/- mice to create chondrogenic organoids in vitro, confirming ABCA6 deficiency can lead to chondrocyte degeneration via modulating cell cycle and activating cellular senescence. Moreover, transcriptome and metabolomic sequencing analysis on ABCA6-KO chondrocytes unveils that the ABCA6 deficiency inhibits cholesterol efflux, leading to intracellular cholesterol accumulation and subsequent cellular senescence and impaired chondrogenesis.A disease-causing mutation of ABCA6 is identified for FPD. ABCA6 is correlated with PD occurrence and subsequent OA progression. ABCA6 can serve as a potential target in chondrogenesis and OA treatment by orchestrated intracellular cholesterol efflux and delayed cellular senescence.

How Can Early Stress Influence Later Alzheimer's Disease Risk? Possible Mediators and Underlying Mechanisms

Alzheimer's disease (AD) is a progressive, age-related neurodegenerative disorder to which genetic mutations and risk factors contribute. Evidence is increasing that environmental and lifestyle-related factors, such as exercise, nutrition, education, and exposure to (early-life) stress modify the onset, incidence, and progression of AD. Here, we discuss recent preclinical findings on putative substrates that can explain or contribute to the effects of stress early in life on the risk of developing AD. We focus in particular on stress hormones, neural networks, synapses, mitochondria, nutrient and lipid metabolism, adult neurogenesis, engram cell ensembles, and neuroinflammation. We discuss the idea that stress exposure early in life can alter these processes, either combined or in isolation, thereby reducing the capacity of the brain to resist deleterious consequences of, for example, amyloid-β accumulation, thereby accelerating cognitive decline and progression of Alzheimer-related changes in model systems of the disease. A better understanding of whether experiences early in life also modify trajectories of cognitive decline and pathology in AD and how the substrates discussed translate to humans may help develop novel preventive and/or therapeutic strategies to mitigate the consequences of stressors early in life and increase resilience to developing dementia.

Effect of cholesterol metabolism on hepatolithiasis

Surgical intervention is currently the primary treatment for hepatolithiasis; however, some patients still experience residual stones and high recurrence rates after surgery. Cholesterol metabolism seems to play an important role in hepatolithiasis pathogenesis. A high cholesterol diet is one of the significant reasons for the increasing incidence of hepatolithiasis. Therefore, regular diet and appropriate medical intervention are crucial measures to prevent hepatolithiasis and reduce recurrence rate after surgery. Reducing dietary cholesterol and drugs that increase cholesterol stone solubility are key therapeutic approaches in treating hepatolithiasis. This article discusses the cholesterol metabolic pathways related to the pathogenesis of hepatolithiasis, as well as food intake and targeted therapeutic drugs.

The Effect of Statin Treatment on Synaptogenesis in the Hippocampus

Deranged lipid homeostasis has been implicated in neurodegenerative diseases. Cholesterol reducing compounds such as statins have received special attention for the possibility that they may be able to ameliorate or prevent cognitive loss associated with neurodegeneration. However, there is much dissension concerning the actual effect of statins on cognitive function. The aim of this study is to investigate the effects of pitavastatin on hippocampal synaptogenesis because the hippocampus is crucial for memory formation. We also evaluated the effects of pitavastatin on local hippocampal estrogen synthesized in the hippocampus itself and its effect on Brain-Derived Neurotrophic Factor (BDNF). Using a hippocampal cell line, H19-7, we found that hippocampal neurons exposed to pitavastatin demonstrate a significant reduction in the synaptic marker postsynaptic density protein 95 (psd-95). The pitavastatin treated neurons also exhibited decreased production of local estrogen and their expression of BDNF mRNA was decreased. These results suggest that statins reduce the ability of hippocampal neurons to form synapses by restricting the production of local estrogen. Because neural connections in the hippocampus are crucial for memory formation, our findings implicate statins as medications that may compromise cognitive function.

Pathophysiologic abnormalities in transgenic mice carrying the Alzheimer disease PSEN1 Δ440 mutation

Mutations in PSEN1 were first discovered as a cause of Alzheimer's disease (AD) in 1995, yet the mechanism(s) by which the mutations cause disease still remains unknown. The generation of novel mouse models assessing the effects of different mutations could aid in this endeavor. Here we report on transgenic mouse lines made with the Δ440 PSEN1 mutation that causes AD with parkinsonism:- two expressing the un-tagged human protein and two expressing a HA-tagged version. Detailed characterization of these lines showed that Line 305 in particular, which expresses the untagged protein, develops age-dependent memory deficits and pathologic features, many of which are consistent with features found in AD. Key behavioral and physiological alterations found in the novel 305 line included an age-dependent deficit in spontaneous alternations in the Y-maze, a decrease in exploration of the center of an open field box, a decrease in the latency to fall on a rotarod, a reduction in synaptic strength and pair-pulse facilitation by electrophysiology, and profound alterations to cerebral blood flow regulation. The pathologic alterations found in the line included, significant neuronal loss in the hippocampus and cortex, astrogliosis, and changes in several proteins involved in synaptic and mitochondrial function, Ca2+ regulation, and autophagy. Taken together, these findings suggest that the transgenic lines will be useful for the investigation of AD pathogenesis.

Exploring the Dynamic Changes of Brain Lipids, Lipid Rafts, and Lipid Droplets in Aging and Alzheimer's Disease

Aging induces complex changes in the lipid profiles across different areas of the brain. These changes can affect the function of brain cells and may contribute to neurodegenerative diseases such as Alzheimer's disease. Research shows that while the overall lipid profile in the human brain remains quite steady throughout adulthood, specific changes occur with age, especially after the age of 50. These changes include a slow decline in total lipid content and shifts in the composition of fatty acids, particularly in glycerophospholipids and cholesterol levels, which can vary depending on the brain region. Lipid rafts play a crucial role in maintaining membrane integrity and facilitating cellular signaling. In the context of Alzheimer's disease, changes in the composition of lipid rafts have been associated with the development of the disease. For example, alterations in lipid raft composition can lead to increased accumulation of amyloid β (Aβ) peptides, contributing to neurotoxic effects. Lipid droplets store neutral lipids and are key for cellular energy metabolism. As organisms age, the dynamics of lipid droplets in the brain change, with evidence suggesting a decline in metabolic activity over time. This reduced activity may lead to an imbalance in lipid synthesis and mobilization, contributing to neurodegenerative processes. In model organisms like Drosophila, studies have shown that lipid metabolism in the brain can be influenced by diet and insulin signaling pathways, crucial for maintaining metabolic balance. The interplay between lipid metabolism, oxidative stress, and inflammation is critical in the context of aging and Alzheimer's disease. Lipid peroxidation, a consequence of oxidative stress, can lead to the formation of reactive aldehydes that further damage neurons. Inflammatory processes can also disrupt lipid metabolism, contributing to the pathology of AD. Consequently, the accumulation of oxidized lipids can affect lipid raft integrity, influencing signaling pathways involved in neuronal survival and function.

Relationship between aging and excess body fat with markers of inflammation, skeletal muscle mass and strength in Mexican community-dwelling people

INTRODUCTION

Aging is accompanied by changes in body composition, such as an increase in fat mass (FM), a decrease in skeletal muscle mass index (SMMI) and muscle strength, combined with a chronic inflammatory process (CI).

OBJECTIVE

Determine the relationship between age and excess body fat with markers of chronic inflammation, skeletal muscle mass and strength.

METHODS

A cross-sectional alitical study was carried out in a convenience sample of adults 45 to 59 years old (n = 100) and older adults 60 to 74 years old (n = 133). All participants had their body composition measured with an impedance meter. They were subsequently divided into two groups: (i) with excess fat (WEF), (ii) without excess fat (NEF), in order to relate excess fat and age with inflammation, muscle mass and strength.

RESULTS

NEF adults and older adults had similar values of SMMI (9.1 ± 1.5 vs. 8.8 ± 1.3, p > 0.05) and strength (28 ± 8 vs. 27 ± 8.6, p > 0.05). Likewise, WEF adults showed significantly lower values than NEF adults in the SMMI (7.9 ± 0.8 vs. 9.1 ± 1.5, p < 0.05) and strength (28 ± 8 vs. 22 ± 5, p < 0.001). Also, WEF older adults presented significantly lower values in the SMMI (15.9 ± 1.8 vs. 22.8 ± 5.1, p < 0.05) and strength (17.9 ± 4.8 vs. 27 ± 8.6, p < 0.001).

CONCLUSIONS

Our findings suggest that excess fat mass is a risk factor that has a significantly greater influence than aging per se on the index of skeletal muscle mass and strength.

AIBP controls TLR4 inflammarafts and mitochondrial dysfunction in a mouse model of Alzheimer's disease

Microglia-driven neuroinflammation plays an important role in the development of Alzheimer's disease. Microglia activation is accompanied by the formation and chronic expression of TLR4 inflammarafts, defined as enlarged and cholesterol-rich lipid rafts serving as an assembly platform for TLR4 dimers and complexes of other inflammatory receptors. The secreted apoA-I binding protein (APOA1BP or AIBP) binds TLR4 and selectively targets cholesterol depletion machinery to TLR4 inflammaraft-expressing inflammatory, but not homeostatic microglia. Here we demonstrated that amyloid-beta (Aβ) induced formation of TLR4 inflammarafts in microglia in vitro and in the brain of APP/PS1 mice. Mitochondria in Apoa1bp-/- APP/PS1 microglia were hyperbranched and cupped, which was accompanied by increased reactive oxygen species and the dilated endoplasmic reticulum. The size and number of Aβ plaques and neuronal cell death were significantly increased, and the animal survival was decreased in Apoa1bp-/-APP/PS1 compared to APP/PS1 female mice. These results suggest that AIBP exerts control of TLR4 inflammarafts and mitochondrial dynamics in microglia and plays a protective role in Alzheimer's disease associated oxidative stress and neurodegeneration.

Strategic Design of Tryptophan-Aspartic Acid-Containing Peptide Inhibitors Using Coronin 1 as a Template: Inhibition of Fusion by Enhancing Acyl Chain Order

Enveloped viruses enter the host cell by fusing at the cell membrane or entering the cell via endocytosis and fusing at the endosome. Conventional inhibitors target the viral fusion protein to inactivate it for inducing fusion. These target-specific vis-à-vis virus-specific inhibitors fail to display their inhibitory efficacy against emerging and remerging viral infections. This necessitates the need to develop broad-spectrum entry inhibitors that are effective irrespective of the virus. Using a broad range of targeting techniques, the fusion inhibitors can modify the physical characteristics of the viral membrane, making it less prone to fusion. We have previously shown that two tryptophan-aspartic acid (WD)-containing hydrophobic peptides, TG-23 and GG-21, from coronin 1, a phagosomal protein, inhibit membrane fusion by modulating membrane organization and dynamics. In the present work, we designed two WD-containing hydrophilic peptides, QG-22 and AG-22, using coronin 1 as a template and evaluated their fusion inhibitory efficacies in the absence and presence of membrane cholesterol. Our results demonstrate that QG-22 and AG-22 inhibit membrane fusion irrespective of the concentration of membrane cholesterol. Our measurements of depth-dependent membrane organization and dynamics reveal that they impede fusion by enhancing the acyl chain order. Overall, our results validate the hypothesis of designing fusion inhibitors by modulating the membrane's physical properties. In addition, it demonstrates that chain hydrophobicity might not be a critical determinant for the development of peptide-based fusion inhibitors.

White matter lipid alterations during aging in the rhesus monkey brain

The brain of higher organisms, such as nonhuman primates, is particularly rich in lipids, with a gray to white matter ratio of approximately 40 to 60%. White matter primarily consists of lipids, and during normal aging, it undergoes significant degeneration due to myelin pathology, which includes structural abnormalities, like sheath splitting, and local inflammation. Cognitive decline in normal aging, without neurodegenerative diseases, is strongly linked to myelin pathology. Although the exact cause of myelin damage is unclear, older myelin differs from younger myelin, as shown by electron microscopy and altered expression of myelin-related RNAs. However, changes in lipid composition during brain aging remain poorly understood. This study assessed lipid profiles from the frontal lobe corpus callosum, an area where age-related myelin pathology is linked to cognitive decline. Results showed significant changes in lipids with age, revealing distinct age-related profiles. Some lipids that are enriched in myelin sheaths become more saturated, while important structural components, like ceramides, decrease. Disease-associated biomarkers such as cholesterol ester Che (22:6) and sulfatide ST (42:2) also change in older monkeys. Additionally, gene expression of lipid biosynthetic enzymes declines with age, while lipid peroxidation remains stable in the same brain region. This suggests that changes in lipid biosynthesis, rather than oxidative damage, likely account for the differences in lipid composition. Our findings indicate that myelin in the normal aging monkey brain shows diverse lipid changes, which may relate to age-related myelin pathology and could constitute targets for designing nutrient supplements or drugs to rejuvenate the brain's lipidome.

A Facile LC-MS Method for Profiling Cholesterol and Cholesteryl Esters in Mammalian Cells and Tissues

Cholesterol is central to mammalian lipid metabolism and serves many critical functions in the regulation of diverse physiological processes. Dysregulation in cholesterol metabolism is causally linked to numerous human diseases, and therefore, in vivo, the concentrations and flux of cholesterol and cholesteryl esters (fatty acid esters of cholesterol) are tightly regulated. While mass spectrometry has been an analytical method of choice for detecting cholesterol and cholesteryl esters in biological samples, the hydrophobicity, chemically inert nature, and poor ionization of these neutral lipids have often proved a challenge in developing lipidomics compatible liquid chromatography-mass spectrometry (LC-MS) methods to study them. To overcome this problem, here, we report a reverse-phase LC-MS method that is compatible with existing high-throughput lipidomics strategies and capable of identifying and quantifying cholesterol and cholesteryl esters from mammalian cells and tissues. Using this sensitive yet robust LC-MS method, we profiled different mammalian cell lines and tissues and provide a comprehensive picture of cholesterol and cholesteryl esters content in them. Specifically, among cholesteryl esters, we find that mammalian cells and tissues largely possess monounsaturated and polyunsaturated variants. Taken together, our lipidomics compatible LC-MS method to study this lipid class opens new avenues in understanding systemic and tissue-level cholesterol metabolism under various physiological conditions.

Aging, sex, metabolic and life experience factors: Contributions to neuro-inflammaging in Alzheimer's disease research

Alzheimer's disease (AD) is prevalent around the world, yet our understanding of the disease is still very limited. Recent work suggests that the cornerstone of AD may include the inflammation that accompanies it. Failure of a normal pro-inflammatory immune response to resolve may lead to persistent central inflammation that contributes to unsuccessful clearance of amyloid-beta plaques as they form, neuronal death, and ultimately cognitive decline. Individual metabolic, and dietary (lipid) profiles can differentially regulate this inflammatory process with aging, obesity, poor diet, early life stress and other inflammatory factors contributing to a greater risk of developing AD. Here, we integrate evidence for the interface between these factors, and how they contribute to a pro-inflammatory brain milieu. In particular, we discuss the importance of appropriate polyunsaturated fatty acids (PUFA) in the diet for the metabolism of specialised pro-resolving mediators (SPMs); raising the possibility for dietary strategies to improve AD outlook.

Lanosterol regulates abnormal amyloid accumulation in LECs through the mediation of cholesterol pathway metabolism

Age-related cataract (ARC) is the predominant cause of global blindness, linked to the progressive aging of the lens, oxidative stress, perturbed calcium homeostasis, hydration irregularities, and modifications in crystallin proteins. Currently, surgical intervention remains the sole efficacious remedy, albeit carrying inherent risks of complications that may culminate in irreversible blindness. It is urgent to explore alternative, cost-effective, and uncomplicated treatment modalities for cataracts. Lanosterol has been widely reported to reverse cataracts, but the mechanism of action is not yet clear. In this study, we elucidated the mechanism through which lanosterol operates in the context of cataract reversal. Through the targeted suppression of sterol regulatory element-binding protein 2 (SREBP2) followed by lanosterol treatment, we observed the restoration of lipid metabolism disorders induced by SREBP2 knockdown in lens epithelial cells (LECs). Notably, lanosterol exhibited the ability to effectively counteract amyloid accumulation and cellular apoptosis triggered by lipid metabolism disorders. In summary, our findings suggest that lanosterol, a pivotal intermediate in lipid metabolism, may exert its therapeutic effects on cataracts by influencing lipid metabolism. This study shed light on the treatment and pharmaceutical development targeting Age-related Cataracts (ARC).

Chemical Inhibition of Sterol Biosynthesis

Cholesterol is an essential molecule of life, and its synthesis can be inhibited by both genetic and nongenetic mechanisms. Hundreds of chemicals that we are exposed to in our daily lives can alter sterol biosynthesis. These also encompass various classes of FDA-approved medications, including (but not limited to) commonly used antipsychotic, antidepressant, antifungal, and cardiovascular medications. These medications can interfere with various enzymes of the post-lanosterol biosynthetic pathway, giving rise to complex biochemical changes throughout the body. The consequences of these short- and long-term homeostatic disruptions are mostly unknown. We performed a comprehensive review of the literature and built a catalogue of chemical agents capable of inhibiting post-lanosterol biosynthesis. This process identified significant gaps in existing knowledge, which fall into two main areas: mechanisms by which sterol biosynthesis is altered and consequences that arise from the inhibitions of the different steps in the sterol biosynthesis pathway. The outcome of our review also reinforced that sterol inhibition is an often-overlooked mechanism that can result in adverse consequences and that there is a need to develop new safety guidelines for the use of (novel and already approved) medications with sterol biosynthesis inhibiting side effects, especially during pregnancy.

AIBP controls TLR4 inflammarafts and mitochondrial dysfunction in a mouse model of Alzheimer's disease

Microglia-driven neuroinflammation plays an important role in the development of Alzheimer's disease (AD). Microglia activation is accompanied by the formation and chronic maintenance of TLR4 inflammarafts, defined as enlarged and cholesterol-rich lipid rafts serving as an assembly platform for TLR4 dimers and complexes of other inflammatory receptors. The secreted apoA-I binding protein (APOA1BP or AIBP) binds TLR4 and selectively targets cholesterol depletion machinery to TLR4 inflammaraft expressing inflammatory, but not homeostatic microglia. Here we demonstrated that amyloid-beta (Aβ) induced formation of TLR4 inflammarafts in microglia in vitro and in the brain of APP/PS1 mice. Mitochondria in Apoa1bp-/- APP/PS1 microglia were hyperbranched and cupped, which was accompanied by increased ROS and the dilated ER. The size and number of Aβ plaques and neuronal cell death were significantly increased, and the animal survival was decreased in Apoa1bp-/- APP/PS1 compared to APP/PS1 female mice. These results suggest that AIBP exerts control of TLR4 inflammarafts and mitochondrial dynamics in microglia and plays a protective role in AD associated oxidative stress and neurodegeneration.

Cholesterol-metabolism, plant sterols, and long-term cognitive decline in older people - Effects of sex and APOEe4

Neurodegenerative, vascular, and dementia diseases are linked to dysregulations in cholesterol metabolism. Dietary plant sterols, or phytosterols, may interfere to neurodegeneration and cognitive decline, and have cholesterol-lowering, anti-inflammatory, and antioxidant qualities. Here, we investigated the potential associations between circulating cholesterol precursors and metabolites, triglycerides, and phytosterols with cognitive decline in older people by performing multivariate analysis on 246 participants engaged in a population-based prospective study. In our analysis we considered the potential effect of sex and APOEe4. We reveal particular dysregulations of diet-derived phytosterols and endogenous cholesterol synthesis and metabolism, and their variations over time linked to cognitive decline in the general population. These results are significant to the development of interventions to avoid cognitive decline in older adults and suggest that levels of circulating sterols should be taken into account when evaluating risk.

Microbial metabolites as modulators of host physiology

The gut microbiota is increasingly recognised as a key player in influencing human health and changes in the gut microbiota have been strongly linked with many non-communicable conditions in humans such as type 2 diabetes, obesity and cardiovascular disease. However, characterising the molecular mechanisms that underpin these associations remains an important challenge for researchers. The gut microbiota is a complex microbial community that acts as a metabolic interface to transform ingested food (and other xenobiotics) into metabolites that are detected in the host faeces, urine and blood. Many of these metabolites are only produced by microbes and there is accumulating evidence to suggest that these microbe-specific metabolites do act as effectors to influence human physiology. For example, the gut microbiota can digest dietary complex polysaccharides (such as fibre) into short-chain fatty acids (SCFA) such as acetate, propionate and butyrate that have a pervasive role in host physiology from nutrition to immune function. In this review we will outline our current understanding of the role of some key microbial metabolites, such as SCFA, indole and bile acids, in human health. Whilst many studies linking microbial metabolites with human health are correlative we will try to highlight examples where genetic evidence is available to support a specific role for a microbial metabolite in host health and well-being.

Cholesterol and oxysterols in retinal neuron-glia interactions: relevance for glaucoma

Cholesterol is an essential component of cellular membranes, crucial for maintaining their structural and functional integrity. It is especially important for nervous tissues, including the retina, which rely on high amounts of plasma membranes for the transmission of the nervous signal. While cholesterol is by far the most abundant sterol, the retina also contains cholesterol precursors and metabolites, especially oxysterols, which are bioactive molecules. Cholesterol lack or excess is deleterious and some oxysterols are known for their effect on neuron survival. Cholesterol homeostasis must therefore be maintained. Retinal glial cells, especially Müller cells, the principal glial cells of the vertebrate retina, provide mechanical, nutritional, and metabolic support for the neighboring neurons. Several pieces of evidence indicate that Müller cells are major actors of cholesterol homeostasis in the retina, as it is known for other glial cells in the brain. This process is based on a close cooperation with neurons, and sterols can be signaling molecules participating in glia-neuron interactions. While some implication of cholesterol in age-related macular degeneration is now recognized, based on epidemiological and laboratory data, evidence for its role in glaucoma is still scarce. The association between cholesterolemia and glaucoma is controversial, but experimental data suggest that sterols could take part in the pathological processes. It has been demonstrated that Müller glial cells are implicated in the development of glaucoma through an ambivalent reactive retinal gliosis process. The early steps contribute to maintaining retinal homeostasis and favor the survival of ganglion cells, which are targeted during glaucoma. If gliosis persists, dysregulation of the neuroprotective functions, cytotoxic effects of gliotic Müller cells and disruption of glia-neuron interactions lead to an acceleration of ganglion cell death. Sterols could play a role in the glial cell response to glaucomatous injury. This represents an understudied but attractive topic to better understand glaucoma and conceive novel preventive or curative strategies. The present review describes the current knowledge on i) sterol metabolism in retinal glial cells, ii) the potential role of cholesterol in glaucoma, and iii) the possible relationships between cholesterol and oxysterols, glial cells and glaucoma. Focus is put on glia-neuron interactions.

Neuroproteomic Analysis after SARS-CoV-2 Infection Reveals Overrepresented Neurodegeneration Pathways and Disrupted Metabolic Pathways

Besides respiratory illness, SARS-CoV-2, the causative agent of COVID-19, leads to neurological symptoms. The molecular mechanisms leading to neuropathology after SARS-CoV-2 infection are sparsely explored. SARS-CoV-2 enters human cells via different receptors, including ACE-2, TMPRSS2, and TMEM106B. In this study, we used a human-induced pluripotent stem cell-derived neuronal model, which expresses ACE-2, TMPRSS2, TMEM106B, and other possible SARS-CoV-2 receptors, to evaluate its susceptibility to SARS-CoV-2 infection. The neurons were exposed to SARS-CoV-2, followed by RT-qPCR, immunocytochemistry, and proteomic analyses of the infected neurons. Our findings showed that SARS-CoV-2 infects neurons at a lower rate than other human cells; however, the virus could not replicate or produce infectious virions in this neuronal model. Despite the aborted SARS-CoV-2 replication, the infected neuronal nuclei showed irregular morphology compared to other human cells. Since cytokine storm is a significant effect of SARS-CoV-2 infection in COVID-19 patients, in addition to the direct neuronal infection, the neurons were treated with pre-conditioned media from SARS-CoV-2-infected lung cells, and the neuroproteomic changes were investigated. The limited SARS-CoV-2 infection in the neurons and the neurons treated with the pre-conditioned media showed changes in the neuroproteomic profile, particularly affecting mitochondrial proteins and apoptotic and metabolic pathways, which may lead to the development of neurological complications. The findings from our study uncover a possible mechanism behind SARS-CoV-2-mediated neuropathology that might contribute to the lingering effects of the virus on the human brain.

The translational potential of cholesterol-based therapies for neurological disease

Cholesterol is an important metabolite and membrane component and is enriched in the brain owing to its role in neuronal maturation and function. In the adult brain, cholesterol is produced locally, predominantly by astrocytes. When cholesterol has been used, recycled and catabolized, the derivatives are excreted across the blood-brain barrier. Abnormalities in any of these steps can lead to neurological dysfunction. Here, we examine how precise interactions between cholesterol production and its use and catabolism in neurons ensures cholesterol homeostasis to support brain function. As an example of a neurological disease associated with cholesterol dyshomeostasis, we summarize evidence from animal models of Huntington disease (HD), which demonstrate a marked reduction in cholesterol biosynthesis with clinically relevant consequences for synaptic activity and cognition. In addition, we examine the relationship between cholesterol loss in the brain and cognitive decline in ageing. We then present emerging therapeutic strategies to restore cholesterol homeostasis, focusing on evidence from HD mouse models.

Cholesterol-dependent amyloid β production: space for multifarious interactions between amyloid precursor protein, secretases, and cholesterol

Amyloid β is considered a key player in the development and progression of Alzheimer's disease (AD). Many studies investigating the effect of statins on lowering cholesterol suggest that there may be a link between cholesterol levels and AD pathology. Since cholesterol is one of the most abundant lipid molecules, especially in brain tissue, it affects most membrane-related processes, including the formation of the most dangerous form of amyloid β, Aβ42. The entire Aβ production system, which includes the amyloid precursor protein (APP), β-secretase, and the complex of γ-secretase, is highly dependent on membrane cholesterol content. Moreover, cholesterol can affect amyloidogenesis in many ways. Cholesterol influences the stability and activity of secretases, but also dictates their partitioning into specific cellular compartments and cholesterol-enriched lipid rafts, where the amyloidogenic machinery is predominantly localized. The most complicated relationships have been found in the interaction between cholesterol and APP, where cholesterol affects not only APP localization but also the precise character of APP dimerization and APP processing by γ-secretase, which is important for the production of Aβ of different lengths. In this review, we describe the intricate web of interdependence between cellular cholesterol levels, cholesterol membrane distribution, and cholesterol-dependent production of Aβ, the major player in AD.