Cholesterol esters, synthesized from cholesterol and fatty acyl CoAs by acyl CoA:cholesterol acyltransferase (ACAT) enzymes, are neutral lipids that play important roles in cholesterol absorption, the synthesis and secretion of apolipoprotein (apo) B-containing lipoproteins, and the formation of macrophage foam cells in atherosclerotic lesions. In recent years, our understanding of the biology of ACAT enzymes has increased significantly, and work from this grant, including the identification of ACAT2 and the generation of mutant mice lacking ACAT1 and ACAT2, has contributed significantly to these advances. However, many important questions remain unanswered. The current proposal is organized around specific aims that address some of the most important of these questions. In the first aim, we will use ACAT2-/- mice to investigate the relative atherogenicity of apoB-containing lipoproteins that contain primarily triglycerides, rather than cholesterol esters, in their cores. These experiments will investigate whether triglyceride-rich lipoproteins promote atherosclerosis.
The second aim i s to determine the relationship of ACAT2 expression in the intestine and liver to cholesterol absorption and cholesterol gallstone formation. ACAT2-/- mice will be used to further define the role of ACAT2 in intestinal cholesterol absorption and hepatic very low-density lipoprotein secretion. We will also test the hypothesis that ACAT2 deficiency in the intestine is protective against gallstone formation, whereas selective ACAT2 deficiency in the liver promotes gallstone formation.
The third aim i s to determine whether cholesterol ester synthesis by ACAT1 and ACAT2 are coupled with distinct cellular functions. Experiments utilizing adenovirus-mediated gene transfer and gene """"""""knock-ins"""""""" are proposed to determine if both ACAT1 and ACAT2 can synthesize cholesterol esters for secretion in apoB-containing lipoproteins.
The fourth aim i s to determine the function of ACAT enzymes in embryonic development by studying ACAT gene expression during development and investigating the cause of lethality of ACAT1-/-ACAT2-/- embryos.

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Research Project (R01)
Project #
5R01HL057170-07
Application #
6621834
Study Section
Special Emphasis Panel (ZRG1-SSS-T (01))
Program Officer
Applebaum-Bowden, Deborah
Project Start
1997-02-01
Project End
2007-01-31
Budget Start
2003-02-01
Budget End
2004-01-31
Support Year
7
Fiscal Year
2003
Total Cost
$405,000
Indirect Cost
Name
J. David Gladstone Institutes
Department
Type
DUNS #
099992430
City
San Francisco
State
CA
Country
United States
Zip Code
94158
Zhang, Jun; Kelley, Kathryn L; Marshall, Stephanie M et al. (2012) Tissue-specific knockouts of ACAT2 reveal that intestinal depletion is sufficient to prevent diet-induced cholesterol accumulation in the liver and blood. J Lipid Res 53:1144-52
Repa, Joyce J; Buhman, Kimberly K; Farese Jr, Robert V et al. (2004) ACAT2 deficiency limits cholesterol absorption in the cholesterol-fed mouse: impact on hepatic cholesterol homeostasis. Hepatology 40:1088-97
Willner, Emily L; Tow, Bryan; Buhman, Kimberly K et al. (2003) Deficiency of acyl CoA:cholesterol acyltransferase 2 prevents atherosclerosis in apolipoprotein E-deficient mice. Proc Natl Acad Sci U S A 100:1262-7
Fazio, S; Major, A S; Swift, L L et al. (2001) Increased atherosclerosis in LDL receptor-null mice lacking ACAT1 in macrophages. J Clin Invest 107:163-71
Buhman, K K; Accad, M; Novak, S et al. (2000) Resistance to diet-induced hypercholesterolemia and gallstone formation in ACAT2-deficient mice. Nat Med 6:1341-7
Accad, M; Smith, S J; Newland, D L et al. (2000) Massive xanthomatosis and altered composition of atherosclerotic lesions in hyperlipidemic mice lacking acyl CoA:cholesterol acyltransferase 1. J Clin Invest 105:711-9
Buhman, K F; Accad, M; Farese, R V (2000) Mammalian acyl-CoA:cholesterol acyltransferases. Biochim Biophys Acta 1529:142-54
Chen, H C; Farese Jr, R V (2000) DGAT and triglyceride synthesis: a new target for obesity treatment? Trends Cardiovasc Med 10:188-92
Farese Jr, R V; Cases, S; Smith, S J (2000) Triglyceride synthesis: insights from the cloning of diacylglycerol acyltransferase. Curr Opin Lipidol 11:229-34
Cases, S; Novak, S; Zheng, Y W et al. (1998) ACAT-2, a second mammalian acyl-CoA:cholesterol acyltransferase. Its cloning, expression, and characterization. J Biol Chem 273:26755-64

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