Abstract Body (Do not enter title and authors here): Introduction: Atherosclerosis is the leading cause of death globally. Growing evidence suggests that mitochondrial dysfunction plays a significant role in atherosclerosis. However, the progression of mitochondrial energy generation disorders during atherosclerosis development remains unclear. In 2021, our lab indicated that activation of G-Protein Coupled Receptor 55 (GPR55) in human aortic endothelial cells (HAECs) could lead to EC activation, potentially increasing inflammation by altering mitochondrial transcription. EC activation is the central pathological event in atherosclerosis. However, whether and how mitochondrial dysfunction leads to EC activation in vivo and promotes atherosclerosis through the GPR55 pathway is still unknown. Methods: Lysophosphatidylinositol (lysoPI), an endogenous ligand for GPR55 activation, was used as a stimulus (20uM for 24hrs) to treat HAECs for Seahorse mitochondrial stress in vitro analysis. Wild-type mice, apolipoprotein E (ApoE-/-) deficiency mice, and GPR55/ApoE double knockout (DKO) mice were used for bulk RNA sequencing and En face analysis. Results: DKO mice showed a significant decrease in atherogenic lesions compared to ApoE-/- mice. In vitro Mito-stress indicated that GPR55 activation significantly increased basal respiration, spare capacity, maximal respiration, proton leak, and ATP production in HAECs, while inhibition of GPR55 reduced these parameters to basal levels. This suggests that GPR55 activation enhances mitochondrial function without affecting non-mitochondrial oxygen consumption, coupling efficiency, or mitochondrial membrane potential. We also generated a list of 289 genes associated with mitochondrial energy generation genetic disorders. Transcriptomic profiling of these genes in atherogenic mice fed with an HF diet for 3, 6, 12, 32, and 72 weeks showed a downward trend in significantly downregulated OXPHOS genes. This significant downregulation suggests increased OXPHOS biogenesis reprogramming as the disease progresses. Additionally, by comparing upregulated genes in ApoE-/- mice with those downregulated in DKO mice, we identified seven potential genes downstream of GPR55 signaling, including M2, MP, A1, F4, P8, H10, and S2, which are involved in the TCA cycle and metabolism, protein import, and lipid modification. Conclusion: Our study provides the first comprehensive examination of how impairments in mitochondrial OXPHOS biogenesis influence atherosclerosis progression via GPR55 signaling.