Abstract Body (Do not enter title and authors here): Heart failure (HF) is characterized by disordered energy metabolism including impaired mitochondrial oxidation and altered energy substrate preference. In triglyceride (TG) deposit cardiomyovasculopathy (TGCV; ORPHA code 565612), a rare form of HF characterized by impaired fatty acid oxidation (FAO), massive TG accumulation occurs in cardiac muscle and vasculature due to deficiency of adipose triglyceride lipase (ATGL). Since acetyl-CoA carboxylase 2 (ACC2) regulates fatty acid transport into mitochondria for oxidation, we hypothesized that genetic deletion or pharmacologic inhibition of ACC2 may improve cardiac function in the Atgl knockout (KO) mouse model of TGCV. Relative to Atgl KO mice, Atgl/Acc2 double KO mice had reduced cardiac TG accumulation and fibrosis, and significant improvements in cardiac function by echocardiography, locomotor activity, and survival (log-rank p <0.0001). These findings were recapitulated by treatment of Atgl KO mice with TLC-3595, a highly selective, systemic, small molecule ACC2 inhibitor in development for type 2 diabetes (Figure). After a single dose of TLC-3595 to Atgl KO mice, dose-dependent reductions in cardiac malonyl-CoA levels and TG content were observed. Further, in a detailed time-course echocardiographic analysis, Atgl KO mice had reduced left ventricular ejection fraction and evidence of cardiac remodeling which was ameliorated by TLC-3595 treatment. Metabolomic profiling of cardiac tissue revealed ACC2-specific changes, including reduced malonyl-CoA and increased acylcarnitines, consistent with increased FAO with TLC-3595 treatment. Moreover, levels of TCA cycle metabolites and acetylcarnitine were reduced in Atgl KO mice but increased with ACC2 deletion or TLC-3595. In summary, ACC2 deletion or pharmacologic inhibition restored cardiac energy metabolism towards increased FAO in Atgl KO mice, resulting in improved cardiac function and survival. These findings support the therapeutic targeting of ACC2, including with the selective small molecule ACC2 inhibitor TLC-3595, for the treatment of patients with HF associated with FAO deficiency.