apoE Expression Research Articles

TOMM40 regulates hepatocellular and plasma lipid metabolism via an LXR-dependent pathway

The gene encoding TOMM40 (Transporter of Outer Mitochondrial Membrane 40) is adjacent to that encoding APOE, which has a central role in lipid and lipoprotein metabolism. Human genetic variants near APOE and TOMM40 are strongly associated with plasma lipid levels, but a specific role for TOMM40 in lipid metabolism has not been established. We show here that suppression of TOMM40 in human hepatoma cells upregulates expression of APOE and LDLR in part via activation of LXRB (NR1H2) by oxysterols, with consequent increased uptake of VLDL and LDL. This is in part due to disruption of mitochondria-endoplasmic reticulum contact sites, with resulting accrual of reactive oxygen species and non-enzymatically derived oxysterols. With TOMM40 knockdown, cellular triglyceride and lipid droplet content are increased, effects attributable in part to receptor-mediated VLDL uptake, since lipid staining is significantly reduced by concomitant suppression of either LDLR or APOE. In contrast, cellular cholesterol content is reduced due to LXRB-mediated upregulation of the ABCA1 transporter as well as increased production and secretion of oxysterol-derived cholic acid. Consistent with the findings in hepatoma cells, in vivo knockdown of TOMM40 in mice results in significant reductions of plasma triglyceride and cholesterol concentrations, reduced hepatic cholesterol and increased triglyceride content, and accumulation of lipid droplets leading to development of steatosis. These findings demonstrate a role for TOMM40 in regulating hepatic lipid and plasma lipoprotein levels and identify mechanisms linking mitochondrial function with lipid metabolism.

Small hepatitis B virus surface antigen (SHBs) induces dyslipidemia by suppressing apolipoprotein-AII expression through ER stress-mediated modulation of HNF4α and C/EBPγ.

Persistent infection with hepatitis B virus (HBV) often leads to disruptions in lipid metabolism. Apolipoprotein AII (apoAII) plays a crucial role in lipid metabolism and is implicated in various metabolic disorders. However, whether HBV could regulate apoAII and contribute to HBV-related dyslipidemia and the underlying mechanism remain unclear. This study revealed significant reductions in apoAII expression in HBV-expressing cell lines, the serum, and liver tissues of HBV-transgenic mice. The impact of HBV on apoAII is related to small hepatitis B virus surface antigen (SHBs). Overexpression of SHBs decreased apoAII levels in SHBs-expressing hepatoma cells, transgenic mice, and the serum of HBV-infected patients, whereas suppression of SHBs increased apoAII expression. Mechanistic investigations demonstrated that SHBs repressed the apoAII promoter activity through a HNF4α- and C/EBPγ-dependent manner; SHBs simultaneously upregulated C/EBPγ and downregulated HNF4α by inhibiting the PI3K/AKT signaling pathway through activating endoplasmic reticulum (ER) stress. Serum lipid profile assessments revealed notable decreases in high-density lipoprotein cholesterol (HDL-C), total cholesterol (TC), and triglycerides (TG) in SHBs-transgenic mice compared to control mice. However, concurrent overexpression of apoAII in these mice effectively counteracted these reductions in lipid levels. In HBV patients, SHBs levels were negatively correlated with serum levels of HDL-C, LDL-C, TC, and TG, whereas apoAII levels positively correlated with lipid content. This study underscores that SHBs contributes to dyslipidemia by suppressing the PI3K/AKT pathway via inducing ER stress, leading to altered expression of HNF4α and C/EBPγ, and subsequently reducing apoAII expression.IMPORTANCEThe significance of this study lies in its comprehensive examination of how the hepatitis B virus (HBV), specifically through its small hepatitis B virus surface antigen (SHBs), impacts lipid metabolism-a key aspect often disrupted by chronic HBV infection. By elucidating the role of SHBs in regulating apolipoprotein AII (apoAII), a critical player in lipid processes and associated metabolic disorders, this research provides insights into the molecular pathways contributing to HBV-related dyslipidemia. Discovering that SHBs downregulates apoAII through mechanisms involving the repression of the apoAII promoter via HNF4α and C/EBPγ, and the modulation of the PI3K/AKT signaling pathway via endoplasmic reticulum (ER) stress, adds critical knowledge to HBV pathogenesis. The research also shows an inverse correlation between SHBs expression and key lipid markers in HBV-infected individuals, suggesting that apoAII overexpression could counteract the lipid-altering effects of SHBs, offering new avenues for understanding and managing the metabolic implications of HBV infection.

Evaluation of Selected Plant Phenolics via Beta-Secretase-1 Inhibition, Molecular Docking, and Gene Expression Related to Alzheimer’s Disease

Background: The goal of the current study was to investigate the inhibitory activity of six phenolic compounds, i.e., rosmarinic acid, gallic acid, oleuropein, epigallocatechin gallate (EGCG), 3-hydroxytyrosol, and quercetin, against β-site amyloid precursor protein cleaving enzyme-1 (BACE1), also known as β-secretase or memapsin 2, which is implicated in the pathogenesis of Alzheimer’s disease (AD). Methods and Results: The inhibitory potential against BACE1, molecular docking simulations, as well as neurotoxicity and the effect on the AD-related gene expression of the selected phenolics were tested. BACE1 inhibitory activity was carried out using the ELISA microplate assay via fluorescence resonance energy transfer (FRET) technology. Molecular docking experiments were performed in the human BACE1 active site (PDB code: 2WJO). Neurotoxicity of the compounds was carried out in SH-SY5Y, a human neuroblastoma cell line, by the Alamar Blue method. A gene expression analysis of the compounds on fourteen genes linked to AD was conducted using the real-time polymerase chain reaction (RT-PCR) method. Rosmarinic acid, EGCG, oleuropein, and quercetin (also used as the reference) were able to inhibit BACE1 with their respective IC50 values 4.06 ± 0.68, 1.62 ± 0.12, 9.87 ± 1.01, and 3.16 ± 0.30 mM. The inhibitory compounds were observed to occupy the non-catalytic site of the BACE1. However, hydrogen bonds were found to be present between rosmarinic acid and EGCG and aspartic amino acid D228 in the catalytic site. Oleuropein and quercetin effectively suppressed the expression of PSEN, APOE, and CLU, which are recognized to be linked to the pathogenesis of AD. Conclusions: The outcomes of the work bring quercetin, EGCG, and rosmarinic acid to the forefront as promising BACE1 inhibitors.

Secreted Apoe rewires melanoma cell state vulnerability to ferroptosis.

A major therapeutic barrier in melanoma is the coexistence of diverse cellular states marked by distinct metabolic traits. Transitioning from a proliferative to an invasive melanoma phenotype is coupled with increased ferroptosis vulnerability. However, the regulatory circuits controlling ferroptosis susceptibility across melanoma cell states are unknown. In this work, we identified Apolipoprotein E (APOE) as the top lipid-metabolism gene segregating the melanoma MITFhigh/AXLlow proliferative/ferroptosis-resistant from MITFlow/AXLhigh invasive/ferroptosis-sensitive state. Mechanistically, ApoE secreted by the MITFhigh/AXLlow cells protects the invasive phenotype from ferroptosis-inducing agents by reducing the content of peroxidation-prone polyunsaturated fatty acids and boosting GPX4 levels both in vitro and in vivo. Whole-exome sequencing indicates that APOEhigh expression in patients with melanoma is associated with resistance to ferroptosis, regardless of APOE germline status. In aggregate, we found a ferroptosis-resistance mechanism between melanoma cell states relying on secreted ApoE and APOEhigh expression as a potential biomarker for poor ferroptosis response in melanoma.

Eucommia ulmoides Oliv. leaf extract: Effects on growth, antioxidant capacity, and lipid metabolism in Red swamp crayfish (Procambarus clarkii)

The addition of Eucommia ulmoides Oliv. leaf extract (ELE) enhances growth, immunity and antioxidant capacity in crustaceans, which has not been studied on the red swamp crayfish (Procambarus clarkii). Hence, this study aimed to investigate the effect of ELE on the growth, antioxidant capacity, digestive enzymes activities, and lipid metabolism of red swamp crayfish. A total of 240 individuals of red swamp crayfish were randomly assigned to four groups. Each group was fed with feed a diet supplemented with varying doses of ELE: 0 g/kg (CK), 0.5 g/kg (T2), 1.0 g/kg (T3), and 1.5 g/kg (T4). After 30 days, the results indicated that T2 group exhibited a significantly higher final average weight, weight gain rate, and specific growth rate compared to the CK (P<0.05). Significantly lower feed conversion ratios than the CK (P<0.05) were observed in the T2 and T3 groups. For antioxidant indicators, hepatopancreas superoxide dismutase (SOD) activity was observed to significantly increased in the T3 and T4 groups, while levels of malondialdehyde (MDA) in which were significantly reduced in hepatopancreas and hemolymph (P<0.05). Regarding biochemical indicators and intestinal function, significant enhancement of lipase (LPS) activity was observed in the T2 group, which decreased in the T4, compared to the CK (P<0.05). Moreover, significant decrease of the glucose (GLU), total triglyceride (TG), and total cholesterol (TC) content of the hemolymph (P<0.05) were observed in the T4 group. Transcriptome analysis revealed that differentially expressed genes in the T4 group were primarily enriched in peroxisome proliferator-activated receptor (PPAR), and lipid metabolism pathways. Furthermore, it seems that ELE supplements significantly upregulated the expression of apoa-II, acaox1, acox3, me1, and plin1 in the PPAR signaling pathway to regulate lipid metabolism. In conclusion, 0.5 g/kg and 1.5 g/kg ELL addition amount can enhance growth performance, antioxidant capacity, and lipid metabolism of red swamp crayfish.

Propionate Decreases Microglial Activation but Impairs Phagocytic Capacity in Response to Aggregated Fibrillar Amyloid Beta Protein.

Microglia, the innate immune cell of the brain, are a principal player in Alzheimer's disease (AD) pathogenesis. Their surveillance of the brain leads to interaction with the protein aggregates that drive AD pathogenesis, most notably Amyloid Beta (Aβ). Microglia attempt to clear and degrade Aβ using phagocytic machinery, spurring damaging neuroinflammation in the process. Thus, modulation of the microglial response to Aβ is crucial in mitigating AD pathophysiology. SCFAs, microbial byproducts of dietary fiber fermentation, are blood-brain barrier permeable molecules that have recently been shown to modulate microglial function. It is unclear whether propionate, one representative SCFA, has beneficial or detrimental effects on microglia in AD. Thus, we investigated its impact on microglial Aβ response in vitro. Using a multiomics approach, we characterized the transcriptomic, metabolomic, and lipidomic responses of immortalized murine microglia following 1 h of Aβ stimulation, as well as characterizing Aβ phagocytosis and secretion of reactive nitrogen species. Propionate blunted the early inflammatory response driven by Aβ, downregulating the expression of many Aβ-stimulated immune genes, including those regulating inflammation, the immune complement system, and chemotaxis. Further, it reduced the expression of Apoe and inflammation-promoting Aβ-binding scavenger receptors such as Cd36 and Msr1 in favor of inflammation-dampening Lpl, although this led to impaired phagocytosis. Finally, propionate shifted microglial metabolism, altering phospholipid composition and diverting arginine metabolism, resulting in decreased nitric oxide production. Altogether, our data demonstrate a modulatory role of propionate on microglia that may dampen immune activation in response to Aβ, although at the expense of phagocytic capacity.

Suppression of CNS APOE4 Expression by miRNAs Delivered by the S2 AAVrh.10 Capsid-modified AAV Vector.

The homozygous APOE4 genotype is the major risk factor for the development of early Alzheimer's disease. Genome engineering studies in mouse models of human APOE4-dependent pathology have established that reduction of APOE4 expression can rescue the phenotype. We hypothesized that APOE4 could be suppressed in the CNS of APOE4 homozygotes using adeno-associated virus (AAV) expression of microRNAs (miRNA) designed to hybridize to APOE mRNA. We screened 9 different miRNAs targeting APOE following transfection in HEK293T and Huh7 cells. Optimal APOE suppression was obtained with mir2A (targeting coding region nt330-351) and mirN4 (3' untranslated region nt1142-1162). miRNA expression cassettes were designed with two copies of each of these two miRNAs co-expressed with a mCherry transgene. To optimize delivery of these miRNAs, an engineered AAVrh.10 variant was identified from a screen of multiple peptide insertions into capsid loop IV and substitutions in loop VIII. This led to identifying the AAV.S2 capsid with enhanced transduction of both neurons and glia and enhanced distribution in the brain. The engineered capsid was used to deliver the APOE miRNA suppression cassette to the hippocampus of TRE4 mice (human APOE4 knock-in replacement of the murine apoE locus). Two weeks after intra-hippocampus administration, regional expression of miRNA at the injection site was quantified at the mRNA level relative to an endogenous reference. The AAV.S2 capsid provided 2.31 ± 0.37-fold higher expression of miRNA over that provided by AAVrh.10 (p<0.05). In the targeted region, a single intra-hippocampus AAV.S2 administration suppressed hippocampal APOE4 mRNA levels by 76.5 ± 3.9% compared to 41.3 ± 3.3% with the same cassette delivered by the wildtype AAVrh.10 capsid (p<0.0001). We conclude that an expression cassette with two different miRNAs targeting APOE4 delivered by the AAV.S2 capsid will generate highly significant suppression of APOE4 in the CNS.

Correlation of APOE polymorphism, expression, and plasma levels with cardiac comorbidities among lipodystrophy in HIV-infected patients

Lipodystrophy in HIV-infected patients (LDHIV) includes morphological and metabolic abnormalities, including lipid and glucose metabolism. ApoE plays a role in the transport and clearance of lipoprotein. In the general population, ApoE 112 (rs429358) and 158 (rs7412) polymorphisms were linked to severe dyslipidemia. Therefore, we investigated ApoE polymorphism using PCR-RFLP in 200 HIV patients (100 with HIV-associated lipodystrophy (HIVLD), 100 without HIVLD), as well as 100 healthy controls. We also assessed ApoE expression using qRT-PCR and measured its level using ELISA. The APOE 4/4, 3/4, and 2/4 genotypes have been associated with a decreased risk of HIV-1 infection. (P = 0.0001, OR = 0.18; P = 0.006, OR = 0.87; P = 0.006, OR = 0.09) when compared between HIV-positive individuals and healthy controls. Conversely, APOE allele 2 was linked to a higher risk of acquiring HIV-1 (P = 0.03, OR = 3.02). APOE allele 2 was linked to a higher likelihood of HIVLD severity when compared between patients with and without HIVLD (P = 0.05, OR = 2.82). When comparing patients with HIVLD to healthy controls, the APOE 4/4 and 2/4 genotypes as well as allele 4 were linked with the reduced risk of LDHIV (P = 0.0006, OR = 0.21; P = 0.01, OR = 0.18; P = 0.0002, OR = 0.40). When compared to patients without HIVLD from healthy controls, the ApoE 4/4 genotype, 2 and 4 alleles, were linked to a reduced risk of developing HIVLD (P = 0.0009, OR = 0.14; P = 0.0001, OR = 0.17; P = 0.00001, OR = 0.39). When comparing impaired to normal cholesterol levels in patients without HIVLD, the ApoE 3/4 genotype was linked with the increased risk of impaired cholesterol levels (P = 0.02, OR = 3.37). When comparing impaired and normal glucose levels in patients without HIVLD, the ApoE 4/4 genotype was associated to an elevated risk of impaired glucose levels (P = 0.03, OR = 8.27). In multivariate analysis, independent impaired cholesterol, LDL, and glucose levels were associated with a higher risk of lipodystrophy severity (P = 0.04, OR = 2.33; P = 0.001, OR = 4.05; P = 0.05, OR = 2.63). ApoE expression was up-regulated in LDHIV with a fold change value of 4.02 compared to those without HIVLD. ApoE protein level was found to be higher in patients of the HIVLD group (3.01 mg/dL) compared to those without HIVLD group (2.83 mg/dL). In conclusion, individuals with ApoE allele 2 were at higher risk for HIV-1 acquisition and severity of HIVLD, whereas those with ApoE allele 4 were at reduced HIVLD severity and development risk. It’s possible that ApoE’s increased level and its overexpression are related to the ApoE allele 2 in HIVLD patients. The development of LDHIV may be facilitated by the APOE 3/4 and 4/4 genotypes as well as abnormal glucose and cholesterol levels.

Heterogeneity of tumor microenvironment cell groups in inflammatory and adenomatous polyposis coli mutant colorectal cancer based on single cell sequencing.

The prognosis of colorectal cancer (CRC) is known to vary across different etiologies. Inflammatory bowel disease (IBD) is often identified as a factor contributing to poorer outcomes. However, the mechanisms that link IBD to a worse CRC prognosis remain to be elucidated. We aim to reveal the complex tumor microenvironment of inflammatory CRC and provide a weak theoretical basis for the treatment of different subtypes of CRC. We conducted a bioinformatics analysis using single-cell RNA sequencing (scRNA-seq) data from 8,494 individual CRC cells derived from azoxymethane (AOM)/dextran sodium sulfate (DSS) and adenomatous polyposis coli (APC) mutant datasets. The expression of implicated genes in both tumor and adjacent normal tissues was examined via immunohistochemistry and immunofluorescence. CRC from AOM/DSS treatment contained fewer immune cells relative to APC-mutant CRC. However, a macrophage subcluster enriched for inflammatory factors was more prevalent in AOM/DSS datasets. This subcluster exhibited elevated expression of APOE and BNIP3. Immunofluorescence and immunohistochemistry of patient samples confirmed that the expression of APOE and BNIP3 was higher in adjacent normal tissues compared to tumors. Our findings shed light on the heterogeneous microenvironments in IBD and APC-mutant CRC. Furthermore, we identify APOE as a potential biomarker for CRC recurrence.

Thyroid Hormone and Alzheimer's: Bridging Epidemiology to Mechanism.

The identification of critical factors that can worsen the mechanisms contributing to the pathophysiology of Alzheimer's is paramount. Thyroid hormones (TH) fit this criterion. Epidemiological studies have identified an association between altered circulating TH levels and Alzheimer's. The study of human and animal models indicates that TH can affect all the main cellular, molecular, and genetic mechanisms known as hallmarks of Alzheimer's. This is true not only for the excessive production in the brain of protein aggregates leading to amyloid plaques and neurofibrillary tangles but also for the clearance of these molecules from the brain parenchyma via the blood-brain barrier and for the escalated process of neuroinflammation-and even for the effects of carrying Alzheimer's-associated genetic variants. Suboptimal TH levels result in a greater accumulation of protein aggregates in the brain. The direct TH regulation of critical genes involved in amyloid beta production and clearance is remarkable, affecting the expression of multiple genes, including APP (related to amyloid beta production), APOE, LRP1, TREM2, AQP4, and ABCB1 (related to amyloid beta clearance). TH also affects microglia by increasing their migration and function and directly regulating the immunosuppressor gene CD73, impacting the immune response of these cells. Studies aiming to understand the mechanisms that could explain how changes in TH levels can contribute to the brain alterations seen in patients with Alzheimer's are ongoing. These studies have potential implications for the management of patients with Alzheimer's and ultimately can contribute to devising new interventions for these conditions.

The enhancer RNA, AANCR, regulates APOE expression in astrocytes and microglia.

Enhancers, critical regulatory elements within the human genome, are often transcribed into enhancer RNAs. The dysregulation of enhancers leads to diseases collectively termed enhanceropathies. While it is known that enhancers play a role in diseases by regulating gene expression, the specific mechanisms by which individual enhancers cause diseases are not well understood. Studies of individual enhancers are needed to fill this gap. This study delves into the role of APOE-activating noncoding RNA, AANCR, in the central nervous system, elucidating its function as a genetic modifier in Alzheimer's Disease. We employed RNA interference, RNaseH-mediated degradation, and single-molecule RNA fluorescence in situ hybridization to demonstrate that mere transcription of AANCR is insufficient; rather, its transcripts are crucial for promoting APOE expression. Our findings revealed that AANCR is induced by ATM-mediated ERK phosphorylation and subsequent AP-1 transcription factor activation. Once activated, AANCR enhances APOE expression, which in turn imparts an inflammatory phenotype to astrocytes. These findings demonstrate that AANCR is a key enhancer RNA in some cell types within the nervous system, pivotal for regulating APOE expression and influencing inflammatory responses, underscoring its potential as a therapeutic target in neurodegenerative diseases.

Retinal debris triggers cytotoxic damage in cocultivated primary porcine RPE cells.

One of the most common causes of vision loss in the elderly population worldwide is age-related macular degeneration (AMD). Subsequently, the number of people affected by AMD is estimated to reach approximately 288 million by the year 2040. The aim of this study was to develop an ex vivo model that simulates various aspects of the complex AMD pathogenesis. For this purpose, primary porcine retinal pigment epithelial cells (ppRPE) were isolated and cultured. One group was exposed to medium containing sodium iodate (NaIO3) to induce degeneration. The others were exposed to different supplemented media, such as bovine serum albumin (BSA), homogenized porcine retinas (HPR), or rod outer segments (ROOS) for eight days to promote retinal deposits. Then, these ppRPE cells were cocultured with porcine neuroretina explants for another eight days. To assess the viability of ppRPE cells, live/dead assay was performed at the end of the study. The positive RPE65 and ZO1 area was evaluated by immunocytochemistry and the expression of RLBP1, RPE65, and TJP1 was analyzed by RT-qPCR. Additionally, drusen (APOE), inflammation (ITGAM, IL6, IL8, NLRP3, TNF), oxidative stress (NFE2L2, SOD1, SOD2), and hypoxia (HIF1A) markers were investigated. The concentration of the inflammatory cytokines IL-6 and IL-8 was determined in medium supernatants from day 16 and 24 via ELISA. Live/dead assay suggests that especially exposure to NaIO3 and HPR induced damage to ppRPE cells, leading in a significant ppRPE cell loss. All supplemented media resulted in decreased RPE-characteristic markers (RPE65; ZO-1) and gene expression like RLBP1 and RPE65 in the cultured ppRPE cells. Besides, some inflammatory, oxidative as well as hypoxic stress markers were altered in ppRPE cells cultivated with NaIO3. The application of HPR induced an enhanced APOE expression. Pre-exposure of the ppRPE cells led to a diminished number of cones in all supplemented media groups compared to controls. Overall, this novel coculture model represents an interesting initial approach to incorporating deposits into coculture to mimic AMD pathogenesis. Nevertheless, the effects of the media used need to be investigated in further studies.

CE9A215 (inotodiol), a lanostane-type oxysterol, mitigates LPS-induced sepsis through multifaceted mechanisms

Dysregulated host response against infection triggers sepsis that leads to multiple organ dysfunction due to uncontrolled inflammatory responses. Despite marked progress in understanding of sepsis, numerous clinical trials for treatment of sepsis have proven daunting and a new therapeutic approach is highly needed. CE9A215 (inotodiol), a fungal secondary metabolite, has been researched for its pharmacological activities and has shown potent anti-allergic effects. In this study, we evaluated the anti-inflammatory activities of CE9A215 upon lipopolysaccharide (LPS) stimulation in vivo and in vitro for the first time. CE9A215 decreased the production of interleukin (IL)-6, tumor necrosis factor alpha (TNF-α), and IL-1β in a concentration-dependent manner in LPS-stimulated RAW264.7 cells. Intriguingly, in human mast cell line LUVA, CE9A215 significantly lowered IL-4 and IL-10, and this effect could be beneficial for the clearance of bacterial infection. In addition, administration of CE9A215 improved the survival rate of LPS-stimulated mice and inhibited the pro-inflammatory cytokines, IL-6, TNF-α, and IL-1β in blood. Moreover, CE9A215 enhanced the expression levels of plasma phospholipid transfer protein (PLTP), apolipoprotein E (ApoE), and ATP-binding cassette transporter (ABCA1) in LPS-stimulated RAW246.7 cells. Liver PLTP level increased significantly in the CE9A215-administered group compared with the control group, which implies that CE9A215 promotes LPS clearance and neutralization by reverse transport of LPS by increasing the expressions of PLTP, ApoE, and ABCA1. Our results highlight CE9A215's potential as a novel therapeutic option for the treatment of sepsis.

Advancements in APOE and dementia research: Highlights from the 2023 AAIC Advancements: APOE conference.

The apolipoprotein E gene (APOE) is an established central player in the pathogenesis of Alzheimer's disease (AD), with distinct apoE isoforms exerting diverse effects. apoE influences not only amyloid-beta and tau pathologies but also lipid and energy metabolism, neuroinflammation, cerebral vascular health, and sex-dependent disease manifestations. Furthermore, ancestral background may significantly impact the link between APOE and AD, underscoring the need for more inclusive research. In 2023, the Alzheimer's Association convened multidisciplinary researchers at the "AAIC Advancements: APOE" conference to discuss various topics, including apoE isoforms and their roles in AD pathogenesis, progress in apoE-targeted therapeutic strategies, updates on disease models and interventions that modulate apoE expression and function. This manuscript presents highlights from the conference and provides an overview of opportunities for further research in the field. Understanding apoE's multifaceted roles in AD pathogenesis will help develop targeted interventions for AD and advance the field of AD precision medicine. APOE is a central player in the pathogenesis of Alzheimer's disease. APOE exerts a numerous effects throughout the brain on amyloid-beta, tau, and other pathways. The AAIC Advancements: APOE conference encouraged discussions and collaborations on understanding the role of APOE.

Effects of the subtypes of apolipoprotein E on immune inhibition and prognosis in patients with Hepatocellular Carcinoma

PurposeTo investigate whether prognosis of patients with hepatocellular carcinoma (HCC) is affected by the abundance and subgroups of myeloid-derived suppressor cells (MDSCs) as well as subtypes and expression of apolipoprotein E (apoE).Methods31 HCC patients were divided into three groups according to blood total apoE level for detecting the abundance of immunoregulatory cells by flow cytometry. Tumour tissue microarrays from 360 HCC patients were evaluated about the abundance and subgroups of MDSCs and the expression of apoE2, apoE3, apoE4 by immunofluorescence staining and immunohistochemistry staining. Survival analysis by means of univariate, multivariate COX regression and Kaplan-Meier methods of the 360 patients was performed based on clinical and pathological examinations along with 10 years’ follow-up data.ResultsThe lower apoE group presented higher abundance of MDSCs in the peripheral blood of HCC patients than higher apoE group. The abundance of monocyte-like MDSCs (M-MDSCs) was higher in the apoE low level group than high level group (p = 0.0399). Lower H-score of apoE2 (HR = 6.140, p = 0.00005) and higher H-score of apoE4 (HR = 7.001, p = 0.009) in tumour tissue were significantly associated with shorter overall survival (OS). The higher infiltration of polymorphonuclear granulocyte-like MDSCs (PMN-MDSCs, HR = 3.762, p = 0.000009) and smaller proportion of M-MDSCs of total cells (HR = 0.454, p = 0.006) in tumour tissue were independent risk factors for shorter recurrence-free survival (RFS).ConclusionThe abundance of MDSCs in HCC patients’ plasma negatively correlates with the level of apoE. The expression of apoE4 in HCC tissue indicated a poor prognosis while apoE2 might be a potential protective factor.

Multiomic analysis of monocyte-derived alveolar macrophages in idiopathic pulmonary fibrosis

BackgroundMonocyte-derived alveolar macrophages (Mo_AMs) are increasingly recognised as potential pathogenic factors for idiopathic pulmonary fibrosis (IPF). While scRNAseq analysis has proven valuable in the transcriptome profiling of Mo_AMs, the integration analysis of multi-omics may provide additional dimensions of understanding of these cellular populations.MethodsWe performed multi-omics analysis on 116 scRNAseq, 119 bulkseq and five scATACseq lung tissue samples from IPF. We built a large-scale IPF scRNAseq atlas and conducted the Monocle 2/3 as well as the Cellchat to explore the developmental path and intercellular communication on Mo_AMs. We also reported the difference in metabolisms, tissue repair and phagocytosis between Mo_AMs and tissue-resident alveolar macrophages (TRMs). To determine whether Mo_AMs affected pulmonary function, we projected clinical phenotypes (FVC%pred) from the bulkseq dataset onto the scRNAseq atlas. Finally, we used scATATCseq to uncover the upstream regulatory mechanisms and determine key drivers in Mo_AMs.ResultsWe identified three Mo_AMs clusters and the trajectory analysis further validated the origin of these clusters. Moreover, via the Cellchat analysis, the CXCL12/CXCR4 axis was found to be involved in the molecular basis of reciprocal interactions between Mo_AMs and fibroblasts through the activation of the ERK pathway in Mo_AMs. SPP1_RecMacs (RecMacs, recruited macrophages) were higher in the low-FVC group than in the high-FVC group. Specifically, compared with TRMs, the functions of lipid and energetic metabolism as well as tissue repair were higher in Mo_AMs than TRMs. But, TRMs may have higher level of phagocytosis than TRMs. SPIB (PU.1), JUNB, JUND, BACH2, FOSL2, and SMARCC1 showed stronger association with open chromatin of Mo_AMs than TRMs. Significant upregulated expression and deep chromatin accessibility of APOE were observed in both SPP1_RecMacs and TRMs.ConclusionThrough trajectory analysis, it was confirmed that SPP1_RecMacs derived from Monocytes. Besides, Mo_AMs may influence FVC% pred and aggravate pulmonary fibrosis through the communication with fibroblasts. Furthermore, distinctive transcriptional regulators between Mo_AMs and TRMs implied that they may depend on different upstream regulatory mechanisms. Overall, this work provides a global overview of how Mo_AMs govern IPF and also helps determine better approaches and intervention therapies.

Adolescent high fat diet alters the transcriptional response of microglia in the prefrontal cortex in response to stressors in both male and female mice

Both obesity and high fat diets (HFD) have been associated with an increase in inflammatory gene expression within the brain. Microglia play an important role in early cortical development and may be responsive to HFD, particularly during sensitive windows, such as adolescence. We hypothesized that HFD during adolescence would increase proinflammatory gene expression in microglia at baseline and potentiate the microglial stress response. Two stressors were examined, a physiological stressor [lipopolysaccharide (LPS), IP] and a psychological stressor [15 min restraint (RST)]. From 3 to 7 weeks of age, male and female mice were fed standard control diet (SC, 20% energy from fat) or HFD (60% energy from fat). On P49, 1 h before sacrifice, mice were randomly assigned to either stressor exposure or control conditions. Microglia from the frontal cortex were enriched using a Percoll density gradient and isolated via fluorescence-activated cell sorting (FACS), followed by RNA expression analysis of 30 genes (27 target genes, three housekeeping genes) using Fluidigm, a medium throughput qPCR platform. We found that adolescent HFD induced sex-specific transcriptional response in cortical microglia, both at baseline and in response to a stressor. Contrary to our hypothesis, adolescent HFD did not potentiate the transcriptional response to stressors in males, but rather in some cases, resulted in a blunted or absent response to the stressor. This was most apparent in males treated with LPS. However, in females, potentiation of the LPS response was observed for select proinflammatory genes, including Tnfa and Socs3. Further, HFD increased the expression of Itgam, Ikbkb, and Apoe in cortical microglia of both sexes, while adrenergic receptor expression (Adrb1 and Adra2a) was changed in response to stressor exposure with no effect of diet. These data identify classes of genes that are uniquely affected by adolescent exposure to HFD and different stressor modalities in males and females.

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.

APOA1 mRNA and serum APOA1 protein as diagnostic and prognostic biomarkers in gastric cancer.

Gastric cancer (GC) remains a formidable challenge in oncology, ranking as a leading cause of cancer mortality globally. This underscores an urgent need for innovative prognostic markers that can revolutionize patient management and outcomes. Recent insights into cancer biology have spotlighted the profound influence of lipid metabolism alterations on tumorigenesis, tumor progression, and the tumor microenvironment. These alterations not only fuel cancer cell growth and proliferation but also play a strategic role in evading immune surveillance and promoting metastasis. The intricate web of lipid metabolism in cancer cells, characterized by deregulated uptake, synthesis, and oxidation of fatty acids (FAs), opens new avenues for targeted therapeutic interventions and prognostic evaluations. Specifically, this study zeroes in on apolipoprotein A-I (APOA1), a key player in lipid metabolism, to unearth its prognostic value in GC. By delving into the role of lipid metabolism-related genes, particularly APOA1, we aim to unveil their potential as groundbreaking biomarkers for GC prognosis. This endeavor not only aims to enhance our understanding of the molecular underpinnings of GC but also to spearhead the development of lipid metabolism-based strategies for improved diagnostic, prognostic, and therapeutic outcomes. Transcriptomic and clinical data from GC patients and healthy individuals were sourced from The Cancer Genome Atlas (TCGA) database, a comprehensive project that molecularly characterizes over 20,000 primary cancer and matched normal samples across 33 cancer types. Significantly differentially expressed lipid metabolism-related genes were identified using the "limma" package in R. Prognostic genes were selected via univariate Cox regression analysis. Differential gene enrichment analysis was performed using Metascape (http://www.metascape.org). The Human Protein Atlas (HPA, https://www.proteinatlas.org) provided information on APOA1 protein expression in GC and healthy tissues. Immune cell infiltration was analyzed using the CIBERSORT algorithm (http://cibersort.stanford.edu). Significant differences in lipid metabolism-related gene expression were observed between GC and normal tissues, closely linked to FA metabolism, oxidoreductase activity, and sphingolipid metabolism. APOA1 emerged as a potential prognostic biomarker by intersecting prognostic and differentially expressed lipid metabolism genes. Immunohistochemical analysis confirmed APOA1 downregulation in GC. The receiver operating characteristic (ROC) analysis demonstrated its predictive value, with the area under the curve (AUC) being 0.64 [95% confidence interval (CI): 0.52-0.76]. APOA1 expression correlated with immune cell infiltrations. Clinical serum APOA1 results revealed lower levels in GC patients (1.38 vs. 1.26; P<0.05), associated with poor prognosis (hazard ratio =1.50; P<0.001) and clinical characteristics. ROC analysis of serum APOA1 demonstrated good diagnostic ability (AUC: 0.63, 95% CI: 0.61-0.65). Serum APOA1 levels significantly increased after treatment. This study highlights lipid metabolism reprogramming in GC and identifies APOA1 as a potential diagnostic and prognostic biomarker, suggesting its clinical utility in managing GC.

Decreased mRNA expression of NR1H3 and ABCA1 in pulmonary tuberculosis patients from population of Punjab, India.

Mycobacterium tuberculosis (MTB) is the causative organism of tuberculosis. Cholesterol is a crucial carbon source required for the survival of MTB in host cells. Transcription factor NR1H3 along with its important target genes ABCA1 and ApoE play important role in removal of extra cholesterol from cells. Changes in the gene expression of NR1H3, ABCA1 and ApoE can affect cholesterol homeostasis and thus the survival of MTB in host cells.Therefore, the present study was designed to analyze the mRNA expression of NR1H3, ABCA1 and ApoE in pulmonary TB (PTB) patients from the population of Punjab, India. In this study, mRNA expression of the transcription factor NR1H3 and its target genes ABCA1 and ApoE was analyzed in 89 subjects, including 41 PTB patients and 48 healthy controls (HCs) by real-time quantitative PCR. It was found that the mRNA expression of both NR1H3 and ABCA1 genes was significantly lower in TB patients than in HCs (p < 0.001). Even after sex-wise stratification of the subjects, mRNA expression of NR1H3 and ABCA1 was found to be down-regulated in both male and female TB patients. No significant difference was observed in expression of ApoE (p = 0.98). The present study found that the mRNA expression of NR1H3 and ABCA1 is down-regulated in TB patients from Punjab state of India.