Dynamic metabolism of endothelial triglycerides protects against atherosclerosis

Blood vessels are continually exposed to circulating lipids and elevations of ApoB containing lipoproteins cause atherosclerosis. Lipoprotein metabolism is highly regulated by lipolysis, largely at the level of the capillary endothelium lining metabolically active tissues. How large blood vessels, the site of atherosclerotic vascular disease, regulate the flux of fatty acids (FA) into triglyceride (TG) rich lipid droplets (LD) is not known. Here, we show that deletion of the enzyme, adipose triglyceride lipase (ATGL) in the endothelium, leads to neutral lipid accumulation in vessels and impairs endothelial dependent vascular tone and nitric oxide synthesis to promote endothelial dysfunction. Mechanistically, the loss of ATGL leads to endoplasmic reticulum stress-induced inflammation, thereby promoting EC dysfunction. Consistent with this mechanism, deletion of endothelial ATGL markedly increases lesion size in a model of atherosclerosis. Together, these data demonstrate that the dynamics of FA flux through LD impacts EC homeostasis and consequently large vessel function during normal physiology and in a chronic disease state Overall design: Endothelial specefic ATGL knockout (ATGL ECKO) and control (Atgl f/f) mice were used in this study to explore the role of lipid droplet breakdown (rate limited by ATGL) on endothelial function. Mice used for single cellRNAseq were injected with AAV8-PCSK9 to raise total cholesterol levels and fed a western type diet for four-weeks. Aorta were harvested from these mice for single cell sequencing.