Abstract: AIM To explore the role of Plin5, a lipid droplet-binding protein involved in the metabolism of lipid droplets in cardiac lipid metabolism in mice by a Plin5 knockout mouse model in vivo and in vitro. METHODS Adult Plin5+/+ and Plin5-/- mice were randomly assigned to wild-type and knockout groups. Echocardiography was recorded for the indexes of left ventricular internal diameter at end-diastole (LVIDd), left ventricular internal diameter at end-systole (LVIDs), left ventricular anterior wall thickness at end-systole (LVWTs) and left ventricular ejection fraction (LVEF). Heart weight and body weight were recorded after sacrifice and heart weight to body weight ratio (HW/BW) was calculated. H/E and Oil Red O staining were used to observe the morphologic changes and cardiac lipid contents, and electron microscopy was used to analyze the changes of mitochondria and lipid droplets. Triacylglycerol (TAG), free fatty acids (FFA), malondialdehyde (MDA) and superoxide dismutase (SOD) contents were also measured and analyzed. RESULTS Plin5-deficient mice exhibited reduced cardiac lipid droplet accumulation with hypertrophied heart and reduced cardiac functions. Plin5 deficiency induced significant oxidative burden in the heart as evidenced by increased MDA content and decreased SOD activity in Plin5 knockout mice hearts and Plin5-/- cardiomyocytes treated with oleic acid. CONCLUSION Plin5 deficiency increases myocardial fatty acid oxidation and oxidative burden, thereby inducing cardiac hypertrophy and cardiac dysfunction.