Angiopoietin-like protein family 4 (Angptl 4) has been shown to regulate lipoprotein metabolism through the inhibition of lipoprotein lipase (LPL). We generated ApoE(-/-)Angptl 4(-/-) mice to study the effect of Angptl 4 deficiency on lipid metabolism and atherosclerosis. Fasting and postolive oil-loaded triglyceride (TG) levels were largely decreased in ApoE(-/-)Angptl 4(-/-) mice compared with and ApoE(-/-)Angptl 4(+/+) mice. There was a significant (75 +/- 12%) reduction in atherosclerotic lesion size in ApoE(-/-)Angptl 4(-/-) mice compared with ApoE(-/-) Angptl 4(+/+) mice. Peritoneal macrophages, isolated from Angptl 4(-/-) mice to investigate the foam cell formation, showed a significant decrease in newly synthesized cholesteryl ester (CE) accumulation induced by acetyl low-density lipoprotein (acLDL) compared with those from Angptl 4(+/+) mice. Thus, genetic knockout of Angptl 4 protects ApoE(-/-) mice against development and progression of atherosclerosis and strongly suppresses the ability of the macrophages to become foam cells in vitro. (C) 2008 Elsevier Inc. All rights reserved.