Abstract Body: Introduction: Fatty acid β-oxidation is a critical metabolic process that prevents lipid accumulation and foam cell formation in macrophages. While mitochondrial oxidation is well-studied, the role of peroxisomal β-oxidation—essential for metabolizing very-long-chain fatty acids (VLCFAs) and branched-chain fatty acids (BCFAs)—remains poorly understood in the context of atherosclerosis.
Hypothesis: We hypothesized that the peroxisomal enzymes Acyl-CoA oxidase 1 (ACOX1) and 2 (ACOX2) regulate VLCFA and BCFA metabolism to maintain macrophage function, and that their loss accelerates atherosclerotic progression.
Methods: We assessed lipid accumulation via BODIPY staining in macrophages treated with various VLCFAs and BCFAs. Peroxisomal fatty acid oxidation was quantified using Seahorse analysis, specifically controlling for mitochondrial contributions. ACOX1/2 expression was suppressed via siRNA or macrophage-specific genetic deletion. Ongoing studies are evaluating atherosclerosis in ACOX-deficient ApoE-/- and PCSK9-induced hyperlipidemic mouse models.
Results: Genes involved in peroxisomal β-oxidation are expressed in macrophages and upregulated during alternative activation. Single-cell RNA sequencing (scRNA-seq) of atherosclerotic plaques revealed significant perturbations in peroxisomal gene expression as lesions progress. Specific VLCFA and BCFA species drove robust fatty acid oxidation, which limited lipid droplet accumulation and prevented apoptosis. Conversely, ACOX1/2 deficiency markedly increased lipid burden and cell death due to impaired oxidation.
Conclusions: These findings identify ACOX1 and ACOX2 as critical regulators of macrophage lipid homeostasis. Impaired peroxisomal oxidation of VLCFAs and BCFAs drives foam cell formation and metabolic dysfunction, suggesting that targeting this pathway may offer a novel therapeutic approach for cardiovascular disease.