Targeted Knockdown of Hepatic SOAT2 With Antisense Oligonucleotides Stabilizes Atherosclerotic Plaque in ApoB100-only LDLr-/- Mice.

OBJECTIVE: To test the hypothesis that the attenuation of cholesterol oleate packaging into apoB-containing lipoproteins will arrest progression of pre-existing atherosclerotic lesions. APPROACH AND RESULTS: Atherosclerosis was induced in apoB-100 only, LDLr(-/-) mice by feeding a diet enriched in cis-monounsaturated fatty acids for 24 weeks. A subset of mice was then euthanized to quantify the extent of atherosclerosis. The remaining mice were continued on the same diet (controls) or assigned to the following treatments for 16 weeks: (1) a diet enriched in n-3 polyunsaturated fatty acids, (2) the cis-monounsaturated fatty acid diet plus biweekly injections of an antisense oligonucleotide specific to hepatic sterol-O-acyltransferase 2 (SOAT2); or (3) the cis-monounsaturated fatty acid diet and biweekly injections of a nontargeting hepatic antisense oligonucleotide. Extent of atherosclerotic lesions in the aorta was monitored morphometrically in vivo with magnetic resonance imaging and ex vivo histologically and immunochemically. Hepatic knockdown of SOAT2 via antisense oligonucleotide treatment arrested lesion growth and stabilized lesions. CONCLUSIONS: Hepatic knockdown of SOAT2 in apoB100-only, LDLr(-/-) mice resulted in remodeling of aortic atherosclerotic lesions into a stable phenotype, suggesting SOAT2 is a viable target for the treatment of atherosclerosis.

Lipid transfer proteins (LTP) and atherosclerosis.

This review deals with four lipid transfer proteins (LTP): three are involved in cholesteryl ester (CE) synthesis or transport, the fourth deals with plasma phospholipid (PL) transfer. Experimental models of atherosclerosis, clinical and epidemiological studies provided information as to the relationship of these LTP(s) to atherosclerosis, which is the main focus of this review. Thus, inhibition of acyl-CoA:cholesterol acyltransferase (ACAT) 1 and 2 decreases cholesterol absorption, plasma cholesterol and aortic cholesterol esterification in the aorta. The discovery that tamoxifen is a potent ACAT inhibitor explained the plasma cholesterol lowering of the drug. The use of ACAT inhibition in humans is under current investigation. As low cholesteryl ester transfer protein (CETP) activity is connected with high HDL-C, several CETP inhibitors were tried in rabbits, with variable results. A new CETP inhibitor, Torcetrapib, was tested in humans and there was a 50-100% increase in HDL-C. Lecithin cholesterol acyl-transferase (LCAT) influences oxidative stress, which can be lowered by transient LCAT gene transfer in LCAT-/- mice. Phospholipid transfer protein (PLTP) deficiency reduced apo B production in apo E-/- mice, as well as oxidative stress in four models of mouse atherosclerosis. In conclusion, the ability to increase HDL-C so markedly by inhibitors of CETP introduces us into a new era in prevention and treatment of coronary heart disease (CHD).

Glisoprenins, new inhibitors of acyl-CoA: cholesterol acyltransferase produced by Gliocladium sp. FO-1513. II. Structure elucidation of glisoprenins A and B.

The structure of glisoprenins A and B, novel acyl-CoA: cholesterol acyltransferase (ACAT) inhibitors, was determined by spectroscopic analyses, mainly 1H and 13C NMR and MS. Glisoprenin A was deduced to be a tetrahydroxynonaprenol and glisoprenin B to be an oxidative modification of glisoprenin A.

Glisoprenins, new inhibitors of acyl-CoA: cholesterol acyltransferase produced by Gliocladium sp. FO-1513. I. Production, isolation and physico-chemical and biological properties.

Gliocladium sp. FO-1513 was found to produce novel inhibitors of acyl-CoA: cholesterol acyltransferase (ACAT). Two active compounds, designated glisoprenins A and B, were isolated from the culture broth of the producing strain by a conventional method. The IC50 values of glisoprenins A and B for ACAT activity were 46 and 61 microM in an enzyme assay using rat liver microsomes, and 1.2 and 0.57 microM in a J774 macrophage assay, respectively.

ACAT inhibitors as antiatherosclerotic agents: compounds and mechanisms.

Atherosclerosis is a major death cause in western industrialized countries. A diagnosing system, medical prevention, and treatment of atherosclerosis is not sufficient so far. A direct acting antiatherosclerotic agent is eagerly waited. ACAT inhibitor approach could provide such an agent. In the formation of atherosclerosis, cholesteryl esters, which are the lipids which accumulate in atheromatous plaques by an aid of macrophages and smooth muscle cells, forming foam cells, may play an important role. ACAT enzyme is responsible for the acylation of cholesterol to cholesteryl esters, a transformation which can be essential in not only cholesteryl esters accumulation at arterial walls but also the absorption of cholesterol in the intestine and the excretion of cholesterol in the liver. From these points, ACAT inhibitors might work against atherosclerosis in three different ways: first, cholesteryl ester accumulation inhibition at arterial walls could be a direct antiatherosclerotic effect; second, cholesterol absorption inhibition at the intestine; and third, cholesterol excretion acceleration at the liver, while the later two effects would result in a reduction of blood cholesterol level--a major risk factor of atherosclerosis. Taking account of this discussion, the ACAT inhibitors would be potent antiatherosclerotic agents. Medicinal research has been contributing full strength to produce an ultimate compound. These efforts should provide a drug which will be useful to patients.

Enzymatically induced alterations in the structure of rat serum lipoproteins.

Incubation of freshly isolated rat serum induces a large number of changes in the properties of the serum lipoproteins, especially the high density lipoproteins (HDL). The particle diameter of the HDL increases from about 10.4 nm to 12.3 nm and the protein content appears to increase by about 60,000 Daltons. Reactions catalyzed by lecithin:cholesterol acyltransferase (LCAT) lead to a marked decrease in cholesterol and phospholipid content, and an even greater increase in cholesteryl ester content. Especially noteworthy are the marked increases in apoE and apoA-IV which are found associated with HDL as a result of this process. Data indicate that the affinity of apoE and apoA-IV for the HDL particles may be influenced by the proportion of surface to core lipid and by the presence of products of the LCAT reaction. Changes in the apoprotein content of very low density lipoproteins are also observed, with A-I and A-IV appearing in this density interval. All of the above changes can be prevented by the inclusion of 5,5'dithiobis(2-nitrobenzoate) or p-chloromercuriphenylsulfonate during the incubation, or by heat treatment of serum at 56 degrees C for 30 min; these treatments are known to inhibit LCAT activity. It is concluded that LCAT action is the major cause of the various changes in HDL structure that are observed and that alterations in apoprotein content occur to correct the resultant imbalance between core lipid and coverage of this core by amphiphilic components. Increased apoE association with cholesteryl ester-rich HDL may provide an efficient means for receptor-mediated removal of cholesterol from the circulation.