👤 Alexandra Badea

Cardiovascular dysfunction frequently accompanies aging and is often worsened by adverse lifestyle factors and genetic susceptibility. The apolipoprotein E (APOE) gene modulates susceptibility to cardiovascular disease, but how exercise and diet interact with APOE genotype remains insufficiently understood. We investigate the cardioprotective potential of exercise in humanized APOE-targeted replacement mice on control and high-fat diet, using photon-counting computed tomography (PCCT) and deep learning-based image segmentation. This study included 251 male and female mice in mid-to-late life of APOE2, APOE3, and APOE4 genotypes with variation in humanized NOS2 (HN) mediated innate immune response, exercise status (exercised vs. sedentary) and diet (control vs. high-fat). Mice underwent in vivo cine cardiac PCCT imaging following contrast enhancement with liposomal iodine nanoparticles. Stroke volume, ejection fraction, and myocardial mass were derived from automated segmentation of cardiac structures using a 3D U-Net model. We assessed main and interaction effects of genotype, sex, HN status, age, exercise and diet using generalized linear models, while Mann-Whitney U tests assessed effects of exercise within stratified subgroups. Exercise was a significant predictor of improvement in several cardiac functional metrics with a large effect size. The interaction between exercise and diet was a significant predictor of reduced body mass and myocardial mass. Stratified analyses found that exercise improves cardiac functional metrics in APOE4 mice on both diets, and APOE3 mice primarily on control diet, while benefitting HN mice more than non-HN mice. Voluntary exercise can partially rescue cardiac dysfunction induced by high-fat diet in adult APOE-targeted replacement mice, with benefits modulated by genotype, sex, and HN status. APOE4 and HN mice benefitted most from exercise. Contrast-enhanced PCCT combined with deep learning segmentation enables scalable, minimally invasive cardiac phenotyping and reveals interaction effects that are critical for designing precision lifestyle interventions in genetically at-risk populations. Show less

This study evaluates photon-counting CT (PCCT) for the imaging of mouse femurs and investigates how APOE genotype, sex, and humanized nitric oxide synthase (HN) expression influence bone morphology during aging. A custom-built micro-CT system with a photon-counting detector (PCD) was used to acquire dual-energy scans of mouse femur samples. PCCT projections were corrected for tile gain differences, iteratively reconstructed with 20 µm isotropic resolution, and decomposed into calcium and water maps. PCD spatial resolution was benchmarked against an energy-integrating detector (EID) using line profiles through trabecular bone. The contrast-to-noise ratio quantified the effects of iterative reconstruction and material decomposition. Femur features such as mean cortical thickness, mean trabecular spacing (TbSp_mean), and trabecular bone volume fraction (BV/TV) were extracted from calcium maps using BoneJ. The statistical analysis used 57 aged mice representing the APOE22, APOE33, and APOE44 genotypes, including 27 expressing HN. We used generalized linear models (GLMs) to evaluate the main interaction effects of age, sex, genotype, and HN status on femur features and Mann-Whitney U tests for stratified analyses. PCCT outperformed EID-CT in spatial resolution and enabled the effective separation of calcium and water. Female HN mice exhibited reduced BV/TV compared to both male HN and female non-HN mice. While genotype effects were modest, a genotype-by-sex stratified analysis found significant effects of HN status in female APOE22 and APOE44 mice only. Linear regression showed that age significantly decreased cortical thickness and increased TbSp_mean in male mice only. These results demonstrate PCCT's utility for femur analysis and reveal strong effects of sex/HN interaction on trabecular bone health in mice. Show less

Axon growth requires long-range transport of organelles, but how these cargoes recruit their motors and how their traffic is regulated are not fully resolved. In this paper, we identify a new pathway based on the class III PI3-kinase (PIK3C3), ankyrin-B (AnkB), and dynactin, which promotes fast axonal transport of synaptic vesicles, mitochondria, endosomes, and lysosomes. We show that dynactin associates with cargo through AnkB interactions with both the dynactin subunit p62 and phosphatidylinositol 3-phosphate (PtdIns(3)P) lipids generated by PIK3C3. AnkB knockout resulted in shortened axon tracts and marked reduction in membrane association of dynactin and dynein, whereas it did not affect the organization of spectrin-actin axonal rings imaged by 3D-STORM. Loss of AnkB or of its linkages to either p62 or PtdIns(3)P or loss of PIK3C3 all impaired organelle transport and particularly retrograde transport in hippocampal neurons. Our results establish new functional relationships between PIK3C3, dynactin, and AnkB that together promote axonal transport of organelles and are required for normal axon length. Show less