Features of Lipid Metabolism in Humanized ApoE Knockin Rat Models

Imine Derivatives of Benzoxazole Attenuate High-Fat Diet-Induced Hyperlipidemia by Modulation of Lipid-Regulating Genes

Purpose: Hyperlipidemia being the prominent risk factor of cardiovascular diseases and side effects associated with the current lipid-lowering drugs have attracted the interest of scientists in the quest for new alternatives. In view of the diverse pharmacological potentials of benzoxazole (BZX) compounds, this study was designed to evaluate the antihyperlipidemic activity of imine derivatives of BZX in high-fat diet (HFD)-fed rats. Methods: Hyperlipidemia was induced in Sprague-Dawley rats by using HFD for 28 days. On the 28th day, blood samples were collected, and animals having serum triglycerides (TG) greater than 400 mg/dL and total cholesterol (TC) greater than 280 mg/dL were selected for further study. Hyperlipidemic rats were daily treated with either a vehicle or simvastatin (SIM; 20 mg/kg) or BZX compounds (10, 20, and 30 mg/kg), for 12 consecutive days. After the specified time duration, hyperlipidemic biomarkers were evaluated in the blood samples of sacrificed rats. Liver samples were collected for histopathological and mRNA analyses. Binding affinities of BZX derivatives with different targets were assessed by molecular docking. Results: The present study revealed that the BZX derivatives dose-dependently reduced the serum levels of TC, TG, low-density lipoprotein, and very low-density lipoprotein along with improvement in high-density lipoprotein levels. Similarly, all the compounds reduced HFD-induced alanine transaminase and aspartate aminotransferase levels except BZX-4. Histopathology of liver samples demonstrated mild to moderate fatty changes upon treatment with BZX-1, BZX-2, and BZX-4. The hepatic architecture of the BZX-3-treated samples was close to normal, and only mild inflammation was witnessed in these samples. Moreover, all the compounds significantly increased superoxide dismutase and glutathione levels, indicating their antioxidant potentials. Gene expression data showed that BZX-1 and BZX-3 reduced lipid levels by inhibiting HMGCR, APOB, PCSK9, SRB1, and VCAM1 and via improving PPAR-α and APOE mRNA levels. BZX-2 demonstrated its antihyperlipidemic effects mainly due to inhibition of APOB, while BZX-4-mediated effects appeared to be due to attenuation of APOB, PCSK9, and SRB1. BZX derivatives displayed strong binding affinities with HMGCR, APOB, and VCAM1, which suggested that some of the interactions might be required for inhibition of these target proteins. Conclusions: Based on the current findings, it can be concluded that BZX derivatives exert their antihyperlipidemic effects via modulation of multiple lipid-regulating genes.

Relationship of Apolipoprotein E with Alzheimer's Disease and Other Neurological Disorders: An Updated Review

Alzheimer's disease (AD) and other neurodegenerative diseases, for which there is no effective cure, cause great social burden. Apolipoprotein E (APOE) is an important lipid transporter, which has been shown to have a close relationship with AD and other neurological disorders in an increasing number of studies, suggesting its potential as a therapeutic target. In this review, we summarize the recent advances in clinical and basic research on the role of APOE in the pathogenesis of multiple neurological diseases, with an emphasis on the new associations between APOE and AD, and between APOE and depression. The progress of APOE research in Parkinson's disease (PD) and some other neurological diseases is briefly discussed.

Neuronal APOE4 removal protects against tau-mediated gliosis, neurodegeneration and myelin deficits

Apolipoprotein E4 (APOE4) is the strongest known genetic risk factor for late-onset Alzheimer's disease (AD). Conditions of stress or injury induce APOE expression within neurons, but the role of neuronal APOE4 in AD pathogenesis is still unclear. Here we report the characterization of neuronal APOE4 effects on AD-related pathologies in an APOE4-expressing tauopathy mouse model. The selective genetic removal of APOE4 from neurons led to a significant reduction in tau pathology, gliosis, neurodegeneration, neuronal hyperexcitability and myelin deficits. Single-nucleus RNA-sequencing revealed that the removal of neuronal APOE4 greatly diminished neurodegenerative disease-associated subpopulations of neurons, oligodendrocytes, astrocytes and microglia whose accumulation correlated to the severity of tau pathology, neurodegeneration and myelin deficits. Thus, neuronal APOE4 plays a central role in promoting the development of major AD pathologies and its removal can mitigate the progressive cellular and tissue alterations occurring in this model of APOE4-driven tauopathy.

Human ApoE2 Endows Stronger Contractility in Rat Cardiomyocytes Enhancing Heart Function

(1) Background: Apolipoprotein E (ApoE) is a critical plasma apolipoprotein for lipid transport and nonlipid-related functions. Humans possess three isoforms of ApoE (2, 3, and 4). ApoE2, which exhibits beneficial effects on cardiac health, has not been adequately studied. (2) Methods: We investigated the cardiac phenotypes of the humanized ApoE knock-in (hApoE KI) rats and compared to wild-type (WT) and ApoE knock-out (ApoE KO) rats using echocardiography, ultrasound, blood pressure measurements, histology strategies, cell culture, Seahorse XF, cardiomyocyte contractility and intracellular Ca²⁺ tests, and Western blotting; (3) Results: hApoE2 rats exhibited enhanced heart contractile function without signs of detrimental remodeling. Isolated adult hApoE2 cardiomyocytes had faster and stronger sarcomere contractility because of more mitochondrial energy generation and stimulation-induced fast and elevated intracellular Ca²⁺ transient. The abundant energy is a result of elevated mitochondrial function via fatty acid β-oxidation. The fast and elevated Ca²⁺ transient is associated with decreased sarcoplasmic reticulum (SR) Ca²⁺ ATPase (SERCA2) and increased expression of cardiac ryanodine receptor 2 (RyR2) conducting a potent Ca²⁺ release from SR.; (4) Conclusions: Our studies validated the association of polymorphic ApoEs with cardiac health in the rat model, and revealed the possible mechanisms of the protective effect of ApoE2 against heart diseases.

Organotypic Rat Testicular Organoids for the Study of Testicular Maturation and Toxicology

An in vitro system to study testicular maturation in rats, an important model organism for reproductive toxicity, could serve as a platform for high-throughput drug and toxicity screening in a tissue specific context. In vitro maturation of somatic cells and spermatogonia in organ culture systems has been reported. However, this has been a challenge for organoids derived from dissociated testicular cells. Here, we report generation and maintenance of rat testicular organoids in microwell culture for 28 days. We find that rat organoids can be maintained in vitro only at lower than ambient O₂ tension of 15% and organoids cultured at 34°C have higher somatic cell maturation and spermatogonial differentiation potential compared to cultures in 37°C. Upon exposure to known toxicants, phthalic acid mono-2-ethylhexyl ester and cadmium chloride, the organoids displayed loss of tight-junction protein Claudin 11 and altered transcription levels of somatic cell markers that are consistent with previous reports in animal models. Therefore, the microwell-derived rat testicular organoids described here can serve as a novel platform for the study of testicular cell maturation and reproductive toxicity in vitro.