Increased cholesterol biosynthesis and hypercholesterolemia in mice overexpressing squalene synthase in the liver.

Squalene synthase (SS) is the first committed enzyme for cholesterol biosynthesis, located at a branch point in the mevalonate pathway. To examine the role of SS in the overall cholesterol metabolism, we transiently overexpressed mouse SS in the livers of mice using adenovirus-mediated gene transfer. Overexpression of SS increased de novo cholesterol biosynthesis with increased 3-hydroxy-3-methyglutaryl-CoA (HMG-CoA) reductase activity, in spite of the downregulation of its own mRNA expression.

High cholesterol level is essential for myelin membrane growth.

Cholesterol in the mammalian brain is a risk factor for certain neurodegenerative diseases, raising the question of its normal function. In the mature brain, the highest cholesterol content is found in myelin. We therefore created mice that lack the ability to synthesize cholesterol in myelin-forming oligodendrocytes.

Scavenger receptor expressed by endothelial cells I (SREC-I) mediates the uptake of acetylated low density lipoproteins by macrophages stimulated with lipopolysaccharide.

Scavenger receptor expressed by endothelial cells I (SREC-I) is a novel endocytic receptor for acetylated low density lipoprotein (LDL). Here we show that SREC-I is expressed in a wide variety of tissues, including macrophages and aortas. Lipopolysaccharide (LPS) robustly stimulated the expression of SREC-I in macrophages.

Lipid-lowering effects of TAK-475, a squalene synthase inhibitor, in animal models of familial hypercholesterolemia.

The lipid-lowering effects of 1-[2-[(3R,5S)-1-(3-acetoxy-2,2-dimethylpropyl)-7-chloro-1,2,3,5-tetrahydro-2-oxo-5-(2,3-dimethoxyphenyl)-4,1-benzoxazepine-3-yl] acetyl] piperidin-4-acetic acid (TAK-475), a novel squalene synthase inhibitor, were examined in two models of familial hypercholesterolemia, low-density lipoprotein (LDL) receptor knockout mice and Watanabe heritable hyperlipidemic (WHHL) rabbits. Two weeks of treatment with TAK-475 in a diet admixture (0.02% and 0.

Synthesis of novel 4,1-benzoxazepine derivatives as squalene synthase inhibitors and their inhibition of cholesterol synthesis.

Modification of the carboxyl group at the 3-position and introduction of protective groups to the hydroxy group of the 4,1-benzoxazepine derivative 2 (metabolite of 1) were carried out, and the inhibitory activity for squalene synthase and cholesterol synthesis in the liver was investigated. Among these compounds, the glycine derivative 3a and beta-alanine derivative 3f exhibited the most potent inhibition of squalene synthase prepared from HepG2 cells (IC(50) = 15 nM). On the other hand, the piperidine-4-acetic acid derivative 4a, which was prepared by acetylation of 3j, was the most effective inhibitor of cholesterol synthesis in rat liver (ED(50) = 2.

Syntheses of (4,1-benzoxazepine-3-ylidene)acetic acid derivatives and their inhibition of squalene synthase.

The (3,5-trans)-7-chloro-5-(2-chlorophenyl)-2-oxo-1,2,3,5-tetrahydro-4,1-benzoxazepine-3-acetic acid derivatives 1 have been previously identified as potent squalene synthase inhibitors. A series of (4,1-benzoxazepin-3-ylidene)acetic acid derivatives were synthesized and evaluated for their inhibition of rat and human squalene synthase, and the (E)-isomers were found to exhibit potent inhibitory activity, with the same potency as 4,1-benzoxazepine-3-acetic acid derivatives. In contrast the (Z)-isomers did not exhibit significant inhibitory activity, and the active conformation of the 4,1-benzoxazepine-3-acetic acid derivatives was deduced from the folded conformation of the (E)-isomers.

Novel 4,1-benzoxazepine derivatives with potent squalene synthase inhibitory activities.

A series of (3,5-trans)-2-oxo-5-phenyl-1,2,3,5-tetrahydro-4,1-benzoxazepine derivatives were synthesized and evaluated for squalene synthase inhibitory and cholesterol biosynthesis inhibitory activities. Through modification of substituents of the lead compounds 1a and 1b, it was found that 4,1-benzoxazepine-3-acetic acid derivatives with isobutyl and neopentyl groups at the 1-position, the chloro atom at the 7-position, and the chloro and methoxy groups at the 2'-position on the 5-phenyl ring, had potent squalene synthase inhibitory activity. Among such compounds, the 5-(2,3-dimethoxyphenyl) derivative 2t exhibited potent inhibition of cholesterol biosynthesis in HepG2 cells.

Syntheses of fused heterocyclic compounds and their inhibitory activities for squalene synthase.

A variety of fused heterocyclic compounds (2-11) were synthesized as a modification of the lead compound 1a and evaluated for their inhibition of squalene synthase. 4,1-Benzothiazepine derivative 2, 1,4-benzodiazepine derivative 6, 1,3-benzodiazepine derivative 7, 1-benzazepine derivative 9, and 4,1-benzoxazocine derivative 10 potently inhibited squalene synthase activity, whereas the 4,1-benzoxazepine derivatives 1 was the most potent inhibitor. 4,1-Benzothiazepine S-oxide derivative 4, 1,4-benzodiazepine derivative 5, 1,3,4-benzotriazepine derivative 8, and 1,2,3,4-tetrahydroquinoline derivative 11 were found to be weakly active.