Cardiovascular diseases (CVD) are a leading cause of mortality in the United States. Atherosclerosis, marked by cholesterol buildup in arterial walls, significantly increases the risk of prevalent CVDs (e.g. myocardial infarction, stroke). Dysfunction and inflammation of endothelial cells (EC) lining the inside of blood vessels promotes atherosclerotic plaque formation and is associated with CVD development. ECs are in direct contact with the blood and directly exposed to physiological or pathological changes in circulating nutrient levels, but a comprehensive understanding of EC metabolism remains in its infancy. We thus aimed to better understand sources and fates of EC metabolites, with an emphasis on metabolites that are essential for both energy generation and cellular signal transduction - such as acetyl-CoA and nicotinamide adenine dinucleotide (NAD). We first focused on acetyl-CoA, generated by nutrient breakdown into the tricarboxylic acid cycle and required for lipid and cholesterol synthesis. Acetyl-CoA is also the acyl donor for post-translational protein (including histone) acetylation, directly linking nutrient breakdown to post-translation protein and gene regulation. We found that glucose, acetate and long-chain lipids are the primary sources of EC acetyl-CoA. Surprisingly, however, ECs undergoing endothelial-to-mesenchymal transition (EndoMT) - a transdifferentiation event underlying atherosclerosis - specifically required acetate-derived acetyl-CoA to transdifferentiate. ECs also generated acetate de novo from glucose, and this glucose-derived acetate was used for acetylation and stabilization of canonical EndoMT pathway proteins (e.g. ALK5, SMADs). Importantly, inhibiting acetate conversion to acetyl-CoA in ECs reduced atherosclerosis progression. Furthermore, we found that histone deacetylation - long believed to be a potential source of acetate - was a quantitatively minor contributor to intracellular acetyl-CoA metabolism. Finally, we focused on NAD, an electron acceptor required for energy homeostasis and an essential co-factor for activity of several classes of enzymes (sirtuins, PARPs, ADP-ribose hydrolases). We found that oral supplementation of NAD precursors in mice reduced atherosclerosis progression independently of EC NAD production and circulating atherosclerosis risk factors. Collectively, these findings provide fundamental insight into acetyl-CoA/NAD metabolism and atherosclerosis pathogenesis by describing: 1) glucose as a pathological source of acetate that promotes EndoMT; 2) deacetylation as a minor source of intracellular acetate/acetyl-CoA; and 3) NAD precursors as potential therapeutic options for atherosclerosis.