Human Apo Research Articles

Quantitative and Kinetic Proteomics Reveal ApoE Isoform-dependent Proteostasis Adaptations in Mouse Brain.

Apolipoprotein E (ApoE) polymorphisms modify the risk of neurodegenerative disease with the ApoE4 isoform increasing and ApoE2 isoform decreasing risk relative to the 'wild-type control' ApoE3 isoform. To elucidate how ApoE isoforms alter the proteome, we measured relative protein abundance and turnover in transgenic mice expressing a human ApoE gene (isoform 2, 3, or 4). This data provides insight into how ApoE isoforms affect the in vivo synthesis and degradation of a wide variety of proteins. We identified 4849 proteins and tested for ApoE isoform-dependent changes in the homeostatic regulation of ~2700 ontologies. In the brain, we found that ApoE4 and ApoE2 both lead to modified regulation of mitochondrial membrane proteins relative to the wild-type control ApoE3. In ApoE4 mice, this regulation is not cohesive suggesting that aerobic respiration is impacted by proteasomal and autophagic dysregulation. ApoE2 mice exhibited a matching change in mitochondrial matrix proteins and the membrane which suggests coordinated maintenance of the entire organelle. In the liver, we did not observe these changes suggesting that the ApoE-effect on proteostasis is amplified in the brain relative to other tissues. Our findings underscore the utility of combining protein abundance and turnover rates to decipher proteome regulatory mechanisms and their potential role in biology.

Hypertriglyceridemia as a Key Contributor to Abdominal Aortic Aneurysm Development and Rupture: Insights from Genetic and Experimental Models.

Abdominal aortic aneurysm (AAA) is a life-threatening vascular disease without effective medications. This study integrated genetic, proteomic, and metabolomic data to identify causation between increased triglyceride (TG)-rich lipoproteins and AAA risk. Three hypertriglyceridemia mouse models were employed to test the hypothesis that increased plasma TG concentrations accelerate AAA development and rupture. In the angiotensin II-infusion AAA model, most Lpl -deficient mice with severely high plasma TG concentrations died of aortic rupture. Consistently, Apoa5 -deficient mice with moderately increased TG concentrations had accelerated AAA development, while human APOC3 transgenic mice with dramatically increased TG concentrations exhibited aortic dissection and rupture. Increased TG concentrations and palmitate inhibited lysyl oxidase maturation. Administration of antisense oligonucleotide targeting Angptl3 profoundly inhibited AAA progression in human APOC3 transgenic mice and Apoe -deficient mice. These results indicate that hypertriglyceridemia is a key contributor to AAA pathogenesis, highlighting the importance of triglyceride-rich lipoprotein management in treating AAA.

Foam fractionation studies of recombinant human apolipoprotein A-I

Apolipoprotein A-I (apoA-I), the primary protein component of plasma high-density lipoproteins (HDL), is comprised of two structural regions, an N-terminal amphipathic α-helix bundle domain (residues 1–184) and a hydrophobic C-terminal domain (residues 185–243). When a recombinant fusion protein construct [bacterial pelB leader sequence – human apoA-I (1–243)] was expressed in Escherichia coli shaker flask cultures, apoA-I was recovered in the cell lysate. By contrast, when the C-terminal domain was deleted from the construct, large amounts of the truncated protein, apoA-I (1–184), were recovered in the culture medium. Consequently, following pelB leader sequence cleavage in the E. coli periplasmic space, apoA-I (1–184) was secreted from the bacteria. When the pelB-apoA-I (1–184) fusion construct was expressed in a 5 L bioreactor, substantial foam production (~30 L) occurred. Upon foam collection and collapse into a liquid foamate, SDS-PAGE revealed that apoA-I (1–184) was the sole major protein present. Incubation of apoA-I (1–184) with phospholipid vesicles yielded reconstituted HDL (rHDL) particles that were similar in size and cholesterol efflux capacity to those generated with full-length apoA-I. Mass spectrometry analysis confirmed that pelB leader sequence cleavage occurred and that foam fractionation did not result in unwanted protein modifications. The facile nature and scalability of bioreactor-based apolipoprotein foam fractionation provide a novel means to generate a versatile rHDL scaffold protein.

An integration-free induced pluripotent stem cell line from a 42-year-old female donor with the APOE-ε2/ε2 allele

The APOE 4 allele remains the primary genetic risk factor for sporadic Alzheimer’s disease, whereas the APOE 2 allele emerges as a protective factor. Therapeutic approaches in murine models with human APOE alleles, such as modulating APOE levels and converting isoforms, show efficacy. However, there is a lack of in vitro APOE2-mutant human neuronal models. Hence, in this study, we generated human induced pluripotent stem cells (hiPSCs) from the peripheral blood mononuclear blood cells (PMBC) of a 42-year-old female donor carrying the APOE-ε2/ε2 allele. The newly generated hiPSC displayed normal karyotype and could differentiate into three germ layers. Besides, they retained their original genotype and expressed pluripotency markers.

Effect of Apolipoprotein E isoforms on the Abundance and Function of P-glycoprotein in Human Brain Microvascular Endothelial Cells

BackgroundIndividuals with Alzheimer’s disease (AD) often require many medications; however, these medications are dosed using regimens recommended for individuals without AD. This is despite reduced abundance and function of P-glycoprotein (P-gp) at the blood-brain barrier (BBB) in AD, which can impact brain exposure of drugs. The fundamental mechanisms leading to reduced P-gp abundance in sporadic AD remain unknown; however, it is known that the apolipoprotein E (apoE) gene has the strongest genetic link to sporadic AD development, and apoE isoforms can differentially alter BBB function. The aim of this study was to assess if apoE affects P-gp abundance and function in an isoform-dependent manner using a human cerebral microvascular endothelial cell (hCMEC/D3) model.MethodsThis study assessed the impact of apoE isoforms on P-gp abundance (by western blot) and function (by rhodamine 123 (R123) uptake) in hCMEC/D3 cells. Cells were exposed to recombinant apoE3 and apoE4 at 2 – 10 µg/mL over 24 – 72 hours. hCMEC/D3 cells were also exposed for 72 hours to astrocyte-conditioned media (ACM) from astrocytes expressing humanised apoE isoforms.ResultsP-gp abundance in hCMEC/D3 cells was not altered by recombinant apoE4 relative to recombinant apoE3, nor did ACM containing human apoE isoforms alter P-gp abundance. R123 accumulation in hCMEC/D3 cells was also unchanged with recombinant apoE isoform treatments, suggesting no change to P-gp function, despite both abundance and function being altered by positive controls SR12813 (5 µM) and PSC 833 (5 µM), respectively.ConclusionsDifferent apoE isoforms have no direct influence on P-gp abundance or function within this model, and further in vivo studies would be required to address whether P-gp abundance or function are reduced in sporadic AD in an apoE isoform-specific manner.

MTOR inhibition enhances synaptic and mitochondrial function in Alzheimer's disease in an APOE genotype-dependent manner.

Apolipoprotein ε4 (APOE4) carriers develop brain metabolic dysfunctions decades before the onset of Alzheimer's disease (AD). A goal of the study is to identify if rapamycin, an inhibitor for the mammalian target of rapamycin (mTOR) inhibitor, would enhance synaptic and mitochondrial function in asymptomatic mice with human APOE4 gene (E4FAD) before they showed metabolic deficits. A second goal is to determine whether there may be genetic-dependent responses to rapamycin when compared to mice with human APOE3 alleles (E3FAD), a neutral AD genetic risk factor. We fed asymptomatic E4FAD and E3FAD mice with control or rapamycin diets for 16 weeks from starting from 3 months of age. Neuronal mitochondrial oxidative metabolism and excitatory neurotransmission rates were measured using in vivo 1H-[13C] proton-observed carbon-edited magnetic resonance spectroscopy, and isolated mitochondrial bioenergetic measurements using Seahorse. We found that rapamycin enhanced neuronal mitochondrial function, glutamate-glutamine cycling, and TCA cycle rates in the asymptomatic E4FAD mice. In contrast, rapamycin enhances glycolysis, non-neuronal activities, and inhibitory neurotransmission of the E3FAD mice. These findings indicate that rapamycin might be able to mitigate the risk for AD by enhancing brain metabolic functions for cognitively intact APOE4 carriers, and the responses to rapamycin are varied by APOE genotypes. Consideration of precision medicine may be needed for future rapamycin therapeutics.

Risk factors for severe COVID-19 disease increase SARS-CoV-2 infectivity of endothelial cells and pericytes.

Coronavirus disease 2019 (COVID-19) was initially considered a primarily respiratory disease but is now known to affect other organs including the heart and brain. A major route by which COVID-19 impacts different organs is via the vascular system. We studied the impact of apolipoprotein E (APOE) genotype and inflammation on vascular infectivity by pseudo-typed severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) viruses in mouse and human cultured endothelial cells and pericytes. Possessing the APOE4 allele or having existing systemic inflammation is known to enhance the severity of COVID-19. Using targeted replacement human APOE3 and APOE4 mice and inflammation induced by bacterial lipopolysaccharide (LPS), we investigated infection by SARS-CoV-2. Here, we show that infectivity was higher in murine cerebrovascular pericytes compared to endothelial cells and higher in cultures expressing APOE4. Furthermore, increasing the inflammatory state of the cells by prior incubation with LPS increased infectivity into human and mouse pericytes and human endothelial cells. Our findings provide insights into the mechanisms underlying severe COVID-19 infection, highlighting how risk factors such as APOE4 genotype and prior inflammation may exacerbate disease severity by augmenting the virus's ability to infect vascular cells.

Apolipoprotein E4 interferes with lipid metabolism to exacerbate depression-like behaviors in 5xFAD mice.

Apolipoprotein E4 (ApoE4) allele is the strongest genetic risk factor for late-onset Alzheimer's disease, and it can aggravate depressive symptoms in non-AD patients. However, the impact of ApoE4 on AD-associated depression-like behaviors and its underlying pathogenic mechanisms remain unclear. This study developed a 5xFAD mouse model overexpressing human ApoE4 (E4FAD). Behavioral assessments and synaptic function tests were conducted to explore the effects of ApoE4 on cognition and depression in 5xFAD mice. Changes in peripheral and central lipid metabolism, as well as the levels of serotonin (5-HT) and γ-aminobutyric acid (GABA) neurotransmitters in the prefrontal cortex, were examined. In addition, the protein levels of 24-dehydrocholesterol reductase/glycogen synthase kinase-3 beta/mammalian target of rapamycin (DHCR24/GSK3β/mTOR) and postsynaptic density protein 95/calmodulin-dependent protein kinase II/brain-derived neurotrophic factor (PSD95/CaMK-II/BDNF) were measured to investigate the molecular mechanism underlying the effects of ApoE4 on AD mice. Compared with 5xFAD mice, E4FAD mice exhibited more severe depression-like behaviors and cognitive impairments. These mice also exhibited increased amyloid-beta deposition in the hippocampus, increased astrocyte numbers, and decreased expression of depression-related neurotransmitters 5-HT and GABA in the prefrontal cortex. Furthermore, lipid metabolism disorders were observed in E4FAD, manifesting as elevated low-density lipoprotein cholesterol and reduced high-density lipoprotein cholesterol in peripheral blood, decreased cholesterol level in the prefrontal cortex, and reduced expression of key enzymes and proteins related to cholesterol synthesis and homeostasis. Abnormal expression of proteins related to the DHCR24/GSK3β/mTOR and PSD95/CaMK-II/BDNF pathways was also observed. This study found that ApoE4 overexpression exacerbates depression-like behaviors in 5xFAD mice and confirmed that ApoE4 reduces cognitive function in these mice. The mechanism may involve the induction of central and peripheral lipid metabolism disorders. Therefore, modulating ApoE expression or function to restore cellular lipid homeostasis may be a promising therapeutic target for AD comorbid with depression. This study also provided a better animal model for studying AD comorbid with depression.

Temporal Characterization of the Amyloidogenic APPswe/PS1dE9;hAPOE4 Mouse Model of Alzheimer's Disease.

Alzheimer's disease (AD) is a devastating disorder with a global prevalence estimated at 55 million people. In clinical studies administering certain anti-beta-amyloid (Aβ) antibodies, amyloid-related imaging abnormalities (ARIAs) have emerged as major adverse events. The frequency of these events is higher among apolipoprotein ε4 allele carriers (APOE4) compared to non-carriers. To reflect patients most at risk for vascular complications of anti-Aβ immunotherapy, we selected an APPswe/PS1dE9 transgenic mouse model bearing the human APOE4 gene (APPPS1:E4) and compared it with the same APP/PS1 mouse model bearing the human APOE3 gene (APOE ε3 allele; APPPS1:E3). Using histological and biochemical analyses, we characterized mice at three ages: 8, 12, and 16 months. Female and male mice were assayed for general cerebral fibrillar and pyroglutamate (pGlu-3) Aβ deposition, cerebral amyloid angiopathy (CAA), microhemorrhages, apoE and cholesterol composition, astrocytes, microglia, inflammation, lysosomal dysfunction, and neuritic dystrophy. Amyloidosis, lipid deposition, and astrogliosis increased with age in APPPS1:E4 mice, while inflammation did not reveal significant changes with age. In general, APOE4 carriers showed elevated Aβ, apoE, reactive astrocytes, pro-inflammatory cytokines, microglial response, and neuritic dystrophy compared to APOE3 carriers at different ages. These results highlight the potential of the APPPS1:E4 mouse model as a valuable tool in investigating the vascular side effects associated with anti-amyloid immunotherapy.

The transcriptome profiling of diseased mouse aortas discloses a dysregulation of the sympathetic neurotransmission in atherosclerosis

Previous reports suggest an association between the development of atherosclerosis and alterations in the aortic sympathetic nervous system, but there is no agreement on whether atherosclerotic plaques are accompanied by increased or decreased sympathetic innervation in the arterial wall.In the present study, the aortic transcriptional profile of mice with different predisposition to atherosclerosis was investigated to clarify how the expression of genes involved in sympathetic neurotransmission varied.Eight-week-old C57Bl/6J control mice, Apoe knockout mice (EKO), EKO mice overexpressing human apoA-I (EKO/hA-I) and double Apoe/Apoa1 knockout mice (DKO) mice were fed either a standard rodent diet or a Western-type diet for 22 weeks. Atherosclerosis was quantified, and the aortic transcriptome was analyzed by RNAseq. Western-type diet administration deeply modified the aortic transcriptome. In the genetically modified atherosclerosis-prone mouse lines, an upregulated expression of genes associated with the immunomodulatory response was observed, paralleled by a downregulated expression of the genes related to sympathetic nervous system. Functional enrichment analysis indicated that the presence of advanced atherosclerosis was accompanied by reduced neuronal generation, modulation of synapse chemical transmission, and catecholamine biosynthesis, supporting a relationship between atherosclerosis, dyslipidemia, and sympathetic neurotransmission.

Engineering Biomimetic Protein Camouflage for Delivering Peptide/siRNA Nanocomplexes.

For cationic nanoparticles, the spontaneous nanoparticle-protein corona formation and aggregation in biofluids can trigger unexpected biological reactions. Herein, we present a biomimetic strategy for camouflaging the cationic peptide/siRNA nanocomplex (P/Si) with single or dual proteins, which exploits the unique properties of endogenous proteins and stabilizes the cationic P/Si complex for safe and targeted delivery. An in-depth study of the P/Si protein corona (P/Si-PC) formation and protein binding was conducted. The results provided insights into the biochemical and toxicological properties of cationic nanocomplexes and the rationales for engineering biomimetic protein camouflages. Based on this, the human serum albumin (HSA) and apolipoprotein AI (Apo-AI) ranked within the top 20 abundant protein species of P/Si-PC were selected to construct biomimetic HSA-dressed P/Si (P/Si@HSA) and dual protein (HSA and Apo-AI)-dressed P/Si (P/Si@HSA_Apo), given that the dual-protein camouflage plays complementary roles in efficient delivery. A branched cationic peptide (b-HKR) was tailored for siRNA delivery, and their nanocomplexes, including the cationic P/Si and biomimetic protein-dressed P/Si, were produced by a precise microfluidic technology. The biomimetic anionic protein camouflage greatly enhanced P/Si biostability and biocompatibility, which offers a reliable strategy for overcoming the limitation of applying cationic nanoparticles in biofluids and systemic delivery.

APOE Genotype Differentially Regulates Respiratory Motor Plasticity in the Active vs Rest phase

Acute intermittent hypoxia (AIH) elicits respiratory motor plasticity and is emerging as a promising strategy to improve breathing and other (non-respiratory) movements in clinical disorders that end life due to respiratory insuffciency ( e.g., spinal cord injury & ALS). AIH-induced phrenic long-term facilitation (pLTF) is the most commonly studied form of respiratory motor plasticity and presents as a persistent increase in phrenic nerve activity after AIH. Specific factors ( e.g. aging, inflammation, time of day) undermine AIH-induced pLTF. However, little information is available concerning the role of specific genes that regulate AIH-induced phrenic motor plasticity. Apolipoproteins (ApoE) are highly expressed in the central nervous system and function as lipid carriers. The APOE gene is tri-allelic ( E2, E3 and E4); ApoE2 and E3 proteins are associated with neuroprotective and neuro-neutral phenotypes, respectively. ApoE4 impairs synaptic plasticity and is implicated in neurodegeneration, particularly Alzheimer’s Disease. Indeed, we recently discovered that specific APOE alleles predict human expression of mAIH-induced plasticity in cortico-spinal pathways to the phrenic/diaphragm motor system. Initial experiments using human APOE4 knock-in rats demonstrate a causal effect in limiting phrenic motor plasticity (vs APOE3) during the active phase. However, the impact of APOE genotype on respiratory plasticity across the daily rest/active cycle is unknown. We tested the hypothesis that APOE4 undermines AIH-induced pLTF vsAPOE3 in a time-of-day-dependent manner. Anesthetized, vagotomized, paralyzed and ventilated adult (3-4 months) male Sprague-Dawley rats with knock-in humanized (h) APOE3 and h APOE4 were presented with AIH (15,1 min hypoxic episodes; arterial PO2 = 40-50mmHg). During the active phase, AIH-induced pLTF was significantly greater in h APOE3 (33±11%) vs h APOE4 rats (-26±7%; p<0.001; both n=6). In contrast, rest phase AIH-induced pLTF was similar in both h APOE3 and h APOE4 rats (121±12% and 122±5%, respectively; both n=7). These experiments demonstrate a causal relationship whereby APOE genotype and time-of-day interact to undermine AIH-induced pLTF in a manner that is unique to the active phase in rats. Since AIH has emerged as a promising neurotherapeutic to preserve/restore breathing in clinical disorders such as spinal cord injury and neuromuscular disease, understanding how genetic factors and time-of-day of AIH delivery impact phrenic motor plasticity will help identify individuals most/least likely to respond to treatment and reveal new targets for precision interventions of AIH. NIH R01HL148030 (GSM), NIH R01HL149800 (GSM), NIH T32HL134621-5 (ABM). This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Estradiol improves behavior in FAD transgenic mice that express APOE3 but not APOE4 after ovariectomy.

Increasing evidence suggests that female individuals have a higher Alzheimer's disease (AD) risk associated with post-menopausal loss of circulating estradiol (E2). However, clinical data are conflicting on whether E2 lowers AD risk. One potential contributing factor is APOE. The greatest genetic risk factor for AD is APOE4, a factor that is pronounced in female individuals post-menopause. Clinical data suggests that APOE impacts the response of AD patients to E2 replacement therapy. However, whether APOE4 prevents, is neutral, or promotes any positive effects of E2 is unclear. Therefore, our goal was to determine whether APOE modulates the impact of E2 on behavior and AD pathology in vivo. To that end, mice that express human APOE3 (E3FAD) or APOE4 (E4FAD) and overproduce Aβ42 were ovariectomized at either 4 months (early) or 8 months (late) and treated with vehicle or E2 for 4 months. In E3FAD mice, we found that E2 mitigated the detrimental effect of ovariectomy on memory, with no effect on Aβ in the early paradigm and only improved learning in the late paradigm. Although E2 lowered Aβ in E4FAD mice in the early paradigm, there was no impact on learning or memory, possibly due to higher Aβ pathology compared to E3FAD mice. In the late paradigm, there was no effect on learning/memory and Aβ pathology in E4FAD mice. Collectively, these data support the idea that, in the presence of Aβ pathology, APOE impacts the response to E2 supplementation post-menopause.

Metabolomics profiling reveals distinct, sex-specific signatures in serum and brain metabolomes in mouse models of Alzheimer's disease.

Increasing evidence suggests that metabolic impairments contribute to early Alzheimer's disease (AD) mechanisms and subsequent dementia. Signals in metabolic pathways conserved across species can facilitate translation. We investigated differences in serum and brain metabolites between the early-onset 5XFAD and late-onset LOAD1 (APOE4.Trem2*R47H) mouse models of AD to C57BL/6J controls at 6 months of age. We identified sex differences for several classes of metabolites, such as glycerophospholipids, sphingolipids, and amino acids. Metabolic signatures were notably different between brain and serum in both mouse models. The 5XFAD mice exhibited stronger differences in brain metabolites, whereas LOAD1 mice showed more pronounced differences in serum. Several of our findings were consistent with results in humans, showing glycerophospholipids reduction in serum of apolipoprotein E (apoE) ε4 carriers and replicating the serum metabolic imprint of the APOE ε4 genotype. Our work thus represents a significant step toward translating metabolic dysregulation from model organisms to human AD. This was a metabolomic assessment of two mouse models relevant to Alzheimer's disease. Mouse models exhibit broad sex-specific metabolic differences, similar to human study cohorts. The early-onset 5XFAD mouse model primarily alters brain metabolites while the late-onset LOAD1 model primarily changes serum metabolites. Apolipoprotein E (apoE) ε4 mice recapitulate glycerophospolipid signatures of human APOE ε4 carriers in both brain and serum.

KLF13 promotes VSMCs phenotypic dedifferentiation by directly binding to the SM22α promoter.

Krüppel-like factor 13 (KLF13), a zinc finger transcription factor, is considered as a potential regulator of cardiomyocyte differentiation and proliferation during heart morphogenesis. However, its precise role in the dedifferentiation of vascular smooth muscle cells (VSMCs) during atherosclerosis and neointimal formation after injury remains poorly understood. In this study, we investigated the relationship between KLF13 and SM22α expression in normal and atherosclerotic plaques by bioanalysis, and observed a significant increase in KLF13 levels in the atherosclerotic plaques of both human patients and ApoE-/- mice. Knockdown of KLF13 was found to ameliorate intimal hyperplasia following carotid artery injury. Furthermore, we discovered that KLF13 directly binds to the SM22α promoter, leading to the phenotypic dedifferentiation of VSMCs. Remarkably, we observed a significant inhibition of platelet-derived growth factor BB-induced VSMCs dedifferentiation, proliferation, and migration when knocked down KLF13 in VSMCs. This inhibitory effect of KLF13 knockdown on VCMC function was, at least in part, mediated by the inactivation of p-AKT signaling in VSMCs. Overall, our findings shed light on a potential therapeutic target for treating atherosclerotic lesions and restenosis after vascular injury.

Carboxyl-terminal sequences in APOA5 are important for suppressing ANGPTL3/8 activity

Apolipoprotein AV (APOA5) lowers plasma triglyceride (TG) levels by binding to the angiopoietin-like protein 3/8 complex (ANGPTL3/8) and suppressing its capacity to inhibit lipoprotein lipase (LPL) catalytic activity and its ability to detach LPL from binding sites within capillaries. However, the sequences in APOA5 that are required for suppressing ANGPTL3/8 activity have never been defined. A clue to the identity of those sequences was the presence of severe hypertriglyceridemia in two patients harboring an APOA5 mutation that truncates APOA5 by 35 residues ("APOA5Δ35"). We found that wild-type (WT) human APOA5, but not APOA5Δ35, suppressed ANGPTL3/8's ability to inhibit LPL catalytic activity. To pursue that finding, we prepared a mutant mouse APOA5 protein lacking 40 C-terminal amino acids ("APOA5Δ40"). Mouse WT-APOA5, but not APOA5Δ40, suppressed ANGPTL3/8's capacity to inhibit LPL catalytic activity and sharply reduced plasma TG levels in mice. WT-APOA5, but not APOA5Δ40, increased intracapillary LPL levels and reduced plasma TG levels in Apoa5-/- mice (where TG levels are high and intravascular LPL levels are low). Also, WT-APOA5, but not APOA5Δ40, blocked the ability of ANGPTL3/8 to detach LPL from cultured cells. Finally, an antibody against a synthetic peptide corresponding to the last 26 amino acids of mouse APOA5 reduced intracapillary LPL levels and increased plasma TG levels in WT mice. We conclude that C-terminal sequences in APOA5 are crucial for suppressing ANGPTL3/8 activity in vitro and for regulating intracapillary LPL levels and plasma TG levels in vivo.

Discovery of Small Molecule Glycolytic Stimulants for Enhanced ApoE Lipidation in Alzheimer's Disease Cell Model.

Alzheimer's disease (AD) is a progressive neurodegenerative disease characterized by pathophysiological deposits of extracellular amyloid beta (Aβ) peptides and intracellular neurofibrillary tangles of tau. The central role of Aβ in AD pathology is well-established, with its increased deposition attributed mainly to its decreased cerebral clearance. Here, it is noteworthy that apolipoprotein E (ApoE), the most significant risk factor for AD, has been shown to play an isoform-specific role in clearing Aβ deposits (ApoE2 > ApoE3 > ApoE4), owing mainly to its lipidation status. In addition to the pathophysiological Aβ deposits, AD is also characterized by abnormal glucose metabolism, which is a distinct event preceding Aβ deposition. The present study established, for the first time, a possible link between these two major AD etiologies, with glucose metabolism directly influencing ApoE lipidation and its secretion by astrocytes expressing human ApoE4. Specifically, glucose dose-dependently activated liver X receptor (LXR), leading to elevated ABCA1 and ABCG1 protein levels and enhanced ApoE lipidation. Moreover, co-treatment with a glycolytic inhibitor significantly inhibited this LXR activation and subsequent ApoE lipidation, further supporting a central role of glucose metabolism in LXR activation leading to enhanced ApoE lipidation, which may help against AD through potential Aβ clearance. Therefore, we hypothesized that pharmacological agents that can target cellular energy metabolism, specifically aerobic glycolysis, may hold significant therapeutic potential against AD. In this context, the present study also led to the discovery of novel, small-molecule stimulants of astrocytic glucose metabolism, leading to significantly enhanced lipidation status of ApoE4 in astrocytic cells. Three such newly discovered compounds (lonidamine, phenformin, and berberine), owing to their promising cellular effect on the glycolysis-ApoE nexus, warrant further investigation in suitable in vivo models of AD.

Effect of Reconstituted Human Apolipoprotein A-I on Recurrent Ischemic Events in Survivors of Acute MI

BackgroundThe AEGIS-II trial hypothesized that CSL112, an intravenous formulation of human apoA-I, would lower the risk of plaque disruption, decreasing the risk of recurrent events such as myocardial infarction (MI) among high-risk patients with MI. ObjectivesThis exploratory analysis evaluates the effect of CSL112 therapy on the incidence of cardiovascular (CV) death and recurrent MI. MethodsThe AEGIS-II trial was an international, multicenter, randomized, double-blind, placebo-controlled trial that randomized 18,219 high-risk acute MI patients to 4 weekly infusions of apoA-I (6 g CSL112) or placebo. ResultsThe incidence of the composite of CV death and type 1 MI was 11% to 16% lower in the CSL112 group over the study period (HR: 0.84; 95% CI: 0.7-1.0; P = 0.056 at day 90; HR: 0.86; 95% CI: 0.74-0.99; P = 0.048 at day 180; and HR: 0.89; 95% CI: 0.79-1.01; P = 0.07 at day 365). Similarly, the incidence of CV death or any MI was numerically lower in CSL112-treated patients throughout the follow-up period (HR: 0.92; 95% CI: 0.80-1.05 at day 90, HR: 0.89; 95% CI: 0.79-0.996 at day 180, HR: 0.91; 95% CI: 0.83-1.01 at day 365). The effect of CSL112 treatment on MI was predominantly observed for type 1 MI and type 4b (MI due to stent thrombosis). ConclusionsAlthough CSL112 did not significantly reduce the occurrence of the primary study endpoints, patients treated with CSL112 infusions had numerically lower rates of CV death and MI, type-1 MI, and stent thrombosis–related MI compared with placebo. These findings could suggest a role of apoA-I in reducing subsequent plaque disruption events via enhanced cholesterol efflux. Further prospective data would be needed to confirm these observations.

Antibody-mediated targeting of human microglial leukocyte Ig-like receptor B4 attenuates amyloid pathology in a mouse model.

Microglia help limit the progression of Alzheimer's disease (AD) by constraining amyloid-β (Aβ) pathology, effected through a balance of activating and inhibitory intracellular signals delivered by distinct cell surface receptors. Human leukocyte Ig-like receptor B4 (LILRB4) is an inhibitory receptor of the immunoglobulin (Ig) superfamily that is expressed on myeloid cells and recognizes apolipoprotein E (ApoE) among other ligands. Here, we find that LILRB4 is highly expressed in the microglia of patients with AD. Using mice that accumulate Aβ and carry a transgene encompassing a portion of the LILR region that includes LILRB4, we corroborated abundant LILRB4 expression in microglia wrapping around Aβ plaques. Systemic treatment of these mice with an anti-human LILRB4 monoclonal antibody (mAb) reduced Aβ load, mitigated some Aβ-related behavioral abnormalities, enhanced microglia activity, and attenuated expression of interferon-induced genes. In vitro binding experiments established that human LILRB4 binds both human and mouse ApoE and that anti-human LILRB4 mAb blocks such interaction. In silico modeling, biochemical, and mutagenesis analyses identified a loop between the two extracellular Ig domains of LILRB4 required for interaction with mouse ApoE and further indicated that anti-LILRB4 mAb may block LILRB4-mApoE by directly binding this loop. Thus, targeting LILRB4 may be a potential therapeutic avenue for AD.

The following article for this Special Issue was previously published and can be found in its respective issue online: "Detection of early Alzheimer's disease-like molecular alterations in a mouse model expressing human ApoE4".

Detection of early Alzheimer's disease-like molecular alterations in a mouse model expressing human ApoE4 (Published in JNC 166.3 issue) https://onlinelibrary.wiley.com/doi/10.1111/jnc.15904.