Search Results (82)

Neurodegenerative and demyelinating diseases are often associated with impaired cholesterol homeostasis, glial dysfunction, neuroinflammation, and impaired myelin maintenance. Because myelin is highly enriched in cholesterol and other lipids, efficient lipid transport, recycling, and availability are essential for oligodendrocyte function and remyelination. Liver X receptors (LXRα and LXRβ) are lipid-sensitive nuclear receptors that connect cholesterol metabolism with glial responses and myelin regulation. In the CNS, the 24S-hydroxycholesterol (24S-OHC)-LXR-ABCA1/ABCG1-ApoE axis serves as an important regulatory pathway for cholesterol efflux, ApoE-mediated lipid redistribution, microglial handling of myelin-derived lipids, and maintenance of cholesterol availability required for oligodendrocyte maturation and myelin formation. The 24S-OHC generated from cholesterol by CYP46A1 acts as an endogenous LXR ligand and promotes transcription of cholesterol efflux genes such as ABCA1 and ABCG1, along with ApoE-mediated lipid transport. Although previous studies with LXR agonists have focused on oligodendrocyte health and remyelination via inflammatory regulation, translation of LXR agonists remains limited by poor CNS exposure, lack of isoform selectivity, and LXRα-mediated hepatic lipogenesis and metabolic toxicity. These limitations have shifted therapeutic development toward LXRβ-biased agonists, CNS-restricted delivery, partial agonism, and modulation of the CYP46A1/24S-OHC pathway. Overall, LXR signaling represents a mechanistic link among brain cholesterol homeostasis, glial lipid handling, and myelin integrity; therefore, the development of next-generation selective LXR agonists offers substantial potential to restore lipid homeostasis and enhance neuroprotection across neurodegenerative diseases. Full article

Peroxisome proliferator-activated receptors (PPARα, PPARβ/δ, and PPARγ) are ligand-regulated nuclear receptors that coordinate lipid metabolism, glucose homeostasis, inflammation, adipogenesis, differentiation, and disease-associated transcriptional programs. Although early structural models emphasized ligand-dependent stabilization of helix 12 (H12) and the activation function-2 surface (AF-2), evidence from molecular dynamics (MD) simulations, NMR, HDX-MS, crystallography, mutagenesis, and biochemical assays supports a more complex conformational-ensemble mechanism. Apo and ligand-bound PPARs populate multiple functional substates whose distributions are shifted by ligands, RXR heterodimerization, DNA binding, co-regulators, post-translational modifications, and disease-associated mutations. This review summarizes MD and integrative structural studies of PPAR conformational dynamics, isoform-specific behavior, PPAR-RXR and co-regulator interactions, ligand entry, graded activation, inverse agonism, disease-associated mutations, and phosphorylation-dependent regulation. PPARγ is the most extensively characterized isoform, whereas PPARα and particularly PPARβ/δ remain comparatively underexplored by atomistic and enhanced-sampling approaches. MD is most informative when it extends beyond post-docking pose stability and is integrated with long-timescale sampling, free-energy methods, dynamic-network analysis, and experimental validation. Future simulations should increasingly model biologically realistic assemblies containing RXR, DNA, coactivators or corepressors, disease mutations, and post-translational modifications to connect ligand chemistry with receptor allostery, transcriptional output, and disease biology. Full article

Acute elevation in circulating lipids induces reversible insulin resistance and alters triglyceride-rich lipoprotein flux. Whether insulin-regulated remodelling of high-density lipoprotein (HDL)-associated apolipoproteins is altered during defined lipid stress in women with polyendocrine metabolic ovarian syndrome (PMOS) remains unclear. In this exploratory, randomized, cross-over study, 10 healthy women and 12 women with PMOS underwent 5-h saline or lipid infusion, with a hyperinsulinemic–euglycemic clamp commencing at 180 min. Plasma proteomics were performed at baseline, 180 min and 300 min using linear modelling (limma). Lipid infusion induced the coordinated suppression of ApoA1 and ApoE isoforms at 180 min in both groups (FDR-adjusted p < 0.01), followed by partial recovery during hyperinsulinemia. Women with PMOS exhibited greater early suppression of ApoA1 (log₂ fold-change −2.20, p = 0.001) and more persistent suppression of ApoE isoforms at 300 min (ApoE3 log₂ −1.64, p = 0.001). ApoA1 suppression correlated inversely with NEFA exposure during lipid infusion (Spearman ρ = −0.54, p = 0.021). Controlled lipid challenge reveals amplified but reversible dysregulation of HDL-associated apolipoproteins in PMOS, with the preservation of the overall response pattern, but impaired recovery under hyperinsulinemic conditions. These findings suggest impaired adaptation to acute lipid stress in PMOS, with ApoA1 changes appearing to relate more closely to acute NEFA exposure than to clamp-derived insulin sensitivity. Full article

Lipoprotein(a) [Lp(a)] has emerged as a major genetically determined cardiovascular risk factor that extends beyond the traditional low-density lipoprotein cholesterol (LDL-C)-centred model of atherosclerotic disease. Despite optimal LDL-C lowering, a substantial proportion of patients continue to experience cardiovascular events, highlighting the clinical relevance of residual cardiovascular risk. This review summarizes current evidence regarding the epidemiology, genetics, pathophysiology and therapeutic implications of Lp(a) in cardiovascular disease. Epidemiological, genetic, and Mendelian randomization studies consistently demonstrate an independent and likely causal association between elevated Lp(a) and atherosclerotic cardiovascular disease, ischemic stroke, calcific aortic valve stenosis, heart failure, and recurrent cardiovascular events, even in patients with well-controlled LDL-C levels. Lp(a) promotes atherosclerosis through proatherogenic, proinflammatory, and prothrombotic mechanisms, largely mediated by oxidized phospholipids and the structural homology of apolipoprotein(a) with plasminogen. Current guidelines increasingly recognize Lp(a) as a risk-enhancing factor capable of refining cardiovascular risk stratification beyond traditional algorithms, thus recommending measuring Lp(a) at least once in a lifetime in all adults. Accurate measurement and standardization of Lp(a) remain essential in clinical practice due to apo(a) isoform size variability; reporting in molar concentrations (nmol/L) is preferred as it better reflects particle number being less affected by isoform size variations and improves the reliability of cardiovascular risk stratification. Collectively, these findings support the integration of Lp(a) into precision-based cardiovascular prevention strategies and suggest a paradigm shift from an exclusively LDL-centric approach toward genetically informed risk assessment and treatment. Full article

The human APOE gene is polymorphic with three major alleles that encode apolipoprotein (apo) E2, apoE3, and apoE4. Both apoE2 and apoE4 are associated with increased atherosclerosis risk. This study utilized human APOE2, APOE3, and APOE4 gene replacement mice and single-cell RNA sequencing approach to delineate the mechanisms underlying this association. The human APOE2, APOE3, and APOE4 mice were fed a Western-type high fat–cholesterol diet for 16 weeks. Hyperlipidemia and significant atherosclerosis were observed in APOE2 mice but not in APOE3 or APOE4 mice. However, increased vascular inflammation was observed in both APOE2 and APOE4 mice. Single-cell RNA sequencing followed by cluster analysis identified 25 major cell types in the aorta that include various immune cell types, endothelial cells, and various vascular mural cell subsets. Results showed that cells from the APOE2 mice were enriched with genes associated with intracellular lipid accumulation and inflammation, whereas cells from the APOE4 mice displayed elevated oxidative- and/or endoplasmic reticulum-stress and inflammatory response. Thus, apoE2 accelerates atherosclerosis by inducing diet-induced hyperlipidemia and inflammation, while apoE4 does not induce hyperlipidemia but enhances inflammation that may prime the vasculature for atherosclerosis development. The distinct mechanisms by which apoE2 and apoE4 promote atherosclerosis underscore the importance of including apoE genotype information in the design of therapeutics for atherosclerosis intervention. Full article

Backgrounds and Aim: Pancreatic cancer is frequently diagnosed at advanced stages, highlighting the need for biomarkers that are capable of detecting early-stage disease in asymptomatic individuals. Recently, apolipoprotein A2 isoforms (ApoA2-ATQ/AT) have been reported as a new blood biomarker for pancreatic cancer. We recently developed diagnostic models based on 100 highly expressed serum microRNAs (miRNAs) combined with CA19-9; these models achieved high accuracy in terms of distinguishing individuals with pancreatic cancer from healthy individuals. This study aimed to compare the diagnostic performance of these miRNA-based models with that of the ApoA2-ATQ/AT biomarker. Methods: Comprehensive sequencing of serum miRNAs was conducted using samples from 120 pancreatic cancer patients recruited across 14 hospitals, along with 93 healthy controls without cancer. Serum CA19-9 levels, miRNA index values, miRNA+CA19-9 index values, and ApoA2 index values were assessed. miRNA-based indices were derived from classification models built on an automated machine-learning platform. Results: The miRNA model (AUC 0.94; 95% CI 0.91–0.97) and the miRNA+CA19-9 model (AUC 0.99; 95% CI 0.98–1.00) outperformed ApoA2 (AUC 0.89; 95% CI 0.84–0.93) in terms of distinguishing individuals with pancreatic cancer from healthy controls across all stages. In early-stage disease (stages 0–I and 0–II), both miRNA-based models also demonstrated superior performance. Strong negative correlations were observed between the ApoA2 index and both the miRNA model index (r = −0.62) and the miRNA+CA19-9 index (r = −0.63). Conclusions: These findings suggest that miRNA-based diagnostic models, particularly when combined with CA19-9, could serve as powerful tools for the early detection of pancreatic cancer. Full article

Carotenoproteins from marine sponges represent an underexplored class of pigment–protein complexes with distinctive structural and functional properties. Here, we report the isolation and biophysical characterization of a blue carotenoprotein from the sponge Tedania ignis, termed Ti-CP. The protein was purified and shown to consist of two closely related isoforms with molecular masses of approximately 27–29 kDa. Reverse-phase chromatography enabled separation of the apoprotein (ApoTi-CP) and its associated carotenoids, which were identified as oxygenated carotenoids consistent with astaxanthin and mytiloxanthin. Circular dichroism analysis revealed that both Ti-CP and ApoTi-CP are dominated by β-sheet secondary structure and display highly similar conformational profiles. In contrast, dynamic light scattering demonstrated that carotenoid binding is critical for protein stability, as the native form exhibited a compact and monodisperse organization, whereas ApoTi-CP showed pronounced aggregation. Isothermal titration calorimetry revealed that Ti-CP, but not ApoTi-CP, interacts with tetracycline, oxacillin, and streptomycin, indicating that pigment-mediated stabilization modulates ligand binding. Both Ti-CP and ApoTi-CP reduced bacterial viability and biofilm formation in a strain-dependent manner and enhanced antibiotic activity, including synergistic effects against resistant bacteria. Together, these results provide a comprehensive description of a previously uncharacterized sponge carotenoprotein and highlight the dual role of carotenoids in structural stabilization and antimicrobial modulation, reinforcing the biotechnological relevance of marine pigment–protein complexes. Full article

Alzheimer’s Disease (AD) is a neurodegenerative disorder characterized by cognitive decline and memory loss. Among the genetic risk factors linked to AD, the Apolipoprotein E4 (ApoE4) remains the strongest. It is well known that carrying the ApoE4 isoform is associated with advanced AD pathology, blood–brain barrier (BBB) disruption, and changes in lipid metabolism. In this review, we provide an overview of the role of centrally and peripherally produced ApoE in AD. After this introduction, we focus on new findings regarding ApoE4’s effects on AD pathology and BBB function. We then discuss ApoE’s role in lipid metabolism in AD, highlighting examples of lipid changes caused by carrying the ApoE4 isoform. Next, the review explores the implications of ApoE4 isoforms for current treatments—whether they involve anti-amyloid therapy or other pharmacological agents used for AD—emphasizing the importance of personalized medicine approaches for patients with this high-risk allele. This review aims to provide an updated overview of ApoE4’s effects on AD pathology and treatment. By integrating recent discoveries, it underscores the critical need to consider ApoE4 status in both research and clinical settings to enhance therapeutic strategies and outcomes for individuals with AD. Full article

Background/Objectives: Apolipoprotein E (APOE) plays a central role in lipid transport and neuronal cholesterol metabolism. Among its three major isoforms (APOE2, APOE3, and APOE4), the APOE4 variant is the strongest genetic risk factor for late-onset Alzheimer’s disease (AD). However, the structural consequences of specific APOE mutations on protein stability remain poorly understood. Methods: Here, we performed computational saturation mutagenesis and molecular dynamics simulations on the non-lipidated N-terminal fragments of APOE3 and APOE4 to examine how missense mutations affect their structural stability. Results: Based on the folding energy (ΔΔG) calculations, mutations G165W and L155W were particularly destabilizing in APOE4. Molecular dynamics analyses showed that these mutations altered local flexibility and compactness, particularly within the helix 4 region, a key structural element for maintaining APOE’s structural integrity. Conclusions: Our findings, which are state dependent and hypothesis generating, highlight isoform-dependent differences in protein stability and identify regions of structural vulnerability within APOE. These insights enhance our understanding of APOE’s conformational dynamics and may inform future studies on its role in neurodegenerative disease mechanisms. Full article

The cellular prion protein (PrP^C) is studied in prion diseases, where its misfolded isoform (PrP^Sc) leads to neurodegeneration. PrP^C has also been implicated in several physiological functions. The protein is abundant in the nervous system, and it is critical for cell signaling in cellular communication, where it acts as a scaffold for various signaling molecules. The Reelin signaling pathway, implicated both in Alzheimer’s and prion diseases, engages Dab1, an adaptor protein influencing APP processing and amyloid beta deposition. Here, we show, using Prnp knockout models (Prnp^0/0), that PrP^C modulates Reelin signaling, affecting Dab1 activation and downstream phosphorylation in both neuronal cultures and mouse brains. Notably, Prnp^0/0 mice showed reduced responsiveness to Reelin, associated with altered Dab1 phosphorylation and Fyn kinase activity. Even though no direct interaction between PrP^C and Reelin/ApoER2 was found, Prnp^0/0 neurons showed lower NCAM levels, a well-established PrP^C interactor. Prion infection further disrupted the Reelin signaling pathway, thus downregulating Dab1 and Reelin receptors and altering Reelin processing, like Alzheimer’s disease pathology. These findings emphasize PrP^C indirect role in Dab1 signaling via the NCAM and Fyn pathways, which influence synaptic function and neurodegeneration in prion diseases. Full article

Following exposure to trauma, avoidance behavior can be protective but also contribute to severe symptoms and interfere with exposure-based therapy. Extinction of fear conditioning by exposure to the same environment or environmental cues that were present during the initial traumatic event but without including the aversive stimulus or stimuli is often used to study post-traumatic stress disorder (PTSD), a condition characterized by an inability to suppress conditioned fear responses. A limitation of this paradigm is that one cannot avoid the context or cues associated with the initial traumatic event. In contrast, in the passive avoidance test, one can escape the environment associated with the aversive stimulus. Genetic factors might modulate the ability to extinguish fear memory. In this study, we compared the effects of distinct human apoE isoforms on the extinction of contextual fear and passive avoidance memory, as well as on subsequent activity levels, depressive-like behavior, and hippocampal levels of tau, in targeted replacement mice. Full article

Lipid metabolism disorders represent a significant risk factor for the pathogenesis of Alzheimer’s disease (AD). Apolipoprotein E (APOE) has been regarded as a pivotal regulator of lipid homeostasis in the central nervous system (CNS), with polymorphic alleles identified as genetic risk factors for late-onset AD. Despite advances in APOE research and the development of numerous pharmaceutical approaches targeting distinct APOE isoforms, there remain limited treatment approaches for AD that focus on lipid metabolic homeostasis. Consequently, it is necessary to reevaluate the lipid metabolic process in the CNS. Apolipoprotein A1 (APOA-I), a major component of high-density lipoprotein (HDL), plays a crucial role in reverse cholesterol transport from tissues to the liver to maintain lipid homeostasis. Over the past few decades, numerous studies have suggested a connection between reduced APOA-I levels and a higher risk of AD. APOA-I is synthesized exclusively in the liver and intestines, and there is a lack of conclusive evidence supporting its functional significance within the central nervous system, in contrast to APOE, which is produced locally by glial cells and neurons within the CNS. Moreover, APOA-I’s ability to penetrate the blood-brain barrier (BBB) is still poorly understood, which causes its significance in central lipid metabolism and AD pathophysiology to be mainly disregarded. Recent advancements in tracing methodologies have underscored the essential role of APOA-I in regulating lipid metabolism in the CNS. This review aims to elucidate the physiological functions and metabolic pathways of APOA-I, integrating its associations with AD-related pathologies, risk factors, and potential therapeutic targets. Through this discourse, we aim to provide novel insights into the intricate relationship between AD and APOA-I, paving the way for future research in this field. Full article

Lipoprotein (a) [Lp(a)] has been recognized as an independent, inherited, causal risk factor for atherosclerotic cardiovascular disease (ASCVD) and aortic valve stenosis, thus representing a major target of residual CV risk. Currently, no drug has been officially approved for lowering Lp(a) levels, and in clinical practice, Lp(a) is mainly used to (re)define CV risk, particularly in individuals at borderline CV risk and people with a family history of premature coronary heart disease, according to various guidelines. Specific Lp(a)-targeted antisense oligonucleotides (ASOs) and small interfering RNA (siRNA) agents have been developed to produce substantial Lp(a) reductions via the inhibition of apo(a) synthesis in the liver. These drugs are conjugated to N-acetylgalactosamine (GalNAc) to ensure their binding to asialoglycoproteins, which are specifically expressed on the surface of the hepatocytes. Such drugs include pelacarsen (an injectable ASO) and olpasiran, zerlasiran, and lepodisiran (injectable siRNA agents). Muvalaplin represents another therapeutic option to lower Lp(a) levels, since it is an oral selective small molecule inhibitor of Lp(a) formation, thus potentially exerting certain advantages in terms of its clinical use. The present narrative review summarizes the available clinical data on the efficacy and safety of these investigational Lp(a)-lowering therapies, as reported in phase 1 and 2 trials. The effects of these drugs on other [aside from Lp(a)] lipid parameters are also discussed. The phase 3 CV trial outcomes are ongoing for some of these agents (i.e., pelacarsen, olpasiran, and lepodisiran) and are briefly mentioned. Overall, there is an urgent need for evidence-based guidelines on Lp(a) reduction in daily clinical practice, following the results of the phase 3 CV trials, as well as for establishing the ideal Lp(a) quantification method (i.e., using an apo(a) isoform-independent assay with appropriate calibrators, reporting the Lp(a) level in molar units). Full article

Atherosclerotic cardiovascular disease (ASCVD) has long been screened using the traditional lipid profile, mainly focusing on LDL cholesterol. However, despite growing evidence supporting lipoprotein(a) [Lp(a)] as an independent risk factor involved in atherosclerosis, its clinical use remains limited. This review examines the reasons behind the limited use of Lp(a) screening in clinical practice, assessing its role in cardiovascular risk, comparing it to traditional lipid markers and evaluating current assessment methods. It also explores existing and emerging treatments, including gene-silencing therapies, for managing elevated Lp(a) levels. One in four clinicians does not routinely check Lp(a) levels, which proves a lack of awareness amongst them. The reasons for that are implied to be that the cost is too high and that available treatments are scarce. The traditional lipid profile, including LDL, high-density lipoprotein (HDL) and triglycerides, continues to be the gold standard for CV risk assessment. One limitation of using Lp(a) in clinical practice is the significant variability in apo(a) sizes, which results from the presence of multiple isoforms determined by the number of kringle domains. This structural diversity poses challenges in standardizing measurement methods, affecting the accuracy and comparability of results. While statins have a minimal impact on Lp(a), PCSK9-i lowers its levels by 20–25%, although this class is not prescribed primarily for this reason. Lastly, gene-silencing therapies, which achieve the greatest reduction in Lp(a) levels, are still in phase III trials, and there is still a need to examine whether this reduction translates into CV benefits. These limitations should not discourage further research, because ASCVD’s complexity requires a more tailored approach. Current lipid-lowering therapy still fails in a minority of cases, as evidenced by new-onset cardiovascular events in patients with well-controlled LDL levels. There is a need for future interventional studies to assess whether a reduction in Lp(a) by PCSK9-i really translates into CV benefits, independent of LDL. Full article

An apparent “inverse” relationship exists between two seemingly unconnected conditions, Alzheimer’s disease (AD) and cancer, despite sharing similar risk factors, like increased age and obesity. AD is associated with amyloid beta (A$\mathsf{\beta }$) plaques and neurofibrillary tau tangles that cause neural degeneration; cancer, in contrast, is characterized by enhanced cell survival and proliferation. Apolipoprotein E (ApoE) is the main lipoprotein found in the central nervous system and via its high affinity with lipoprotein receptors plays a critical role in cholesterol transport and uptake. ApoE has 3 protein isoforms, ApoE E2, ApoE E3, and ApoE E4, respectively encoded for by 3 allelic variants of APOE ($\mathsf{\epsilon }$2, $\mathsf{\epsilon }$3, and $\mathsf{\epsilon }$4). This review examines the characteristics and function of ApoE described in both AD and cancer to assimilate evidence for its potential contribution to mechanisms that may underly the reported inverse association between the two conditions. Of the genetic risk factors relevant to most cases of AD, the most well-known with the strongest contribution to risk is APOE, specifically the $\mathsf{\epsilon }$4 variant, whereas for cancer risk, APOE has not featured as a significant genetic contributor to risk. However, at the protein level in both conditions, ApoE contributes to disease pathology via affecting lipid physiology and transport. In AD, A$\mathsf{\beta }$-dependent and -independent interactions have been suggested, whereas in cancer, ApoE plays a role in immunoregulation. Understanding the mechanism of action of ApoE in these diametrically opposed diseases may enable differential targeting of therapeutics to provide a beneficial outcome for both. Full article