Potential role of acyl-coenzyme A:cholesterol transferase (ACAT) Inhibitors as hypolipidemic and antiatherosclerosis drugs

Androgen influence on cholesterogenic enzyme mRNA levels in the mouse meibomian gland

PURPOSE

We tested our hypothesis that testosterone increases the meibomian gland gene expression of numerous enzymes in the cholesterol biosynthetic pathway.

METHODS

Meibomian glands were obtained from castrated mice treated with vehicle or testosterone for 2 weeks. Tissues were processed for the analysis of selected mRNAs by real-time PCR.

RESULTS

Our research demonstrates that testosterone stimulates a significant increase in the mRNA levels of mevalonate kinase, phosphomevalonate kinase, mevalonate pyrophosphate decarboxylase, isopentenyl pyrophosphate isomerase, geranylgeranyl pyrophosphate synthase, squalene epoxidase, lanosterol synthase, lanosterol demethylase, and Delta 7-sterol reductase.

CONCLUSIONS

Our findings indicate that androgens may promote cholesterol biosynthesis in the meibomian gland.

Differential cerebral cortex transcriptomes of baboon neonates consuming moderate and high docosahexaenoic acid formulas

BACKGROUND

Docosahexaenoic acid (DHA, 22:6n-3) and arachidonic acid (ARA, 20:4n-6) are the major long chain polyunsaturated fatty acids (LCPUFA) of the central nervous system (CNS). These nutrients are present in most infant formulas at modest levels, intended to support visual and neural development. There are no investigations in primates of the biological consequences of dietary DHA at levels above those present in formulas but within normal breastmilk levels.

METHODS AND FINDINGS

Twelve baboons were divided into three formula groups: Control, with no DHA-ARA; "L", LCPUFA, with 0.33%DHA-0.67%ARA; "L3", LCPUFA, with 1.00%DHA-0.67%ARA. All the samples are from the precentral gyrus of cerebral cortex brain regions. At 12 weeks of age, changes in gene expression were detected in 1,108 of 54,000 probe sets (2.05%), with most showing <2-fold change. Gene ontology analysis assigns them to diverse biological functions, notably lipid metabolism and transport, G-protein and signal transduction, development, visual perception, cytoskeleton, peptidases, stress response, transcription regulation, and 400 transcripts having no defined function. PLA2G6, a phospholipase recently associated with infantile neuroaxonal dystrophy, was downregulated in both LCPUFA groups. ELOVL5, a PUFA elongase, was the only LCPUFA biosynthetic enzyme that was differentially expressed. Mitochondrial fatty acid carrier, CPT2, was among several genes associated with mitochondrial fatty acid oxidation to be downregulated by high DHA, while the mitochondrial proton carrier, UCP2, was upregulated. TIMM8A, also known as deafness/dystonia peptide 1, was among several differentially expressed neural development genes. LUM and TIMP3, associated with corneal structure and age-related macular degeneration, respectively, were among visual perception genes influenced by LCPUFA. TIA1, a silencer of COX2 gene translation, is upregulated by high DHA. Ingenuity pathway analysis identified a highly significant nervous system network, with epidermal growth factor receptor (EGFR) as the outstanding interaction partner.

CONCLUSIONS

These data indicate that LCPUFA concentrations within the normal range of human breastmilk induce global changes in gene expression across a wide array of processes, in addition to changes in visual and neural function normally associated with formula LCPUFA.

Deficiency of adiponectin receptor 2 reduces diet-induced insulin resistance but promotes type 2 diabetes

Adiponectin/adiponectin receptors (AdipoR) are involved in energy homeostasis and inflammatory pathways. To investigate the role of AdipoR2 in metabolic control, we studied the lipid and glucose metabolic phenotypes in AdipoR2-deficient mice. AdipoR2 deletion diminished high-fat diet-induced dyslipidemia and insulin resistance yet deteriorated glucose homeostasis as high-fat feeding continued, which resulted from the failure of pancreatic beta-cells to adequately compensate for the moderate insulin resistance. A defect in the AdipoR2 gene may represent a mechanism underlying the etiology of certain subgroups of type 2 diabetic patients who eventually develop overt diabetes, whereas other obese patients do not.

Synthesis and biological evaluation of unprecedented classes of spiro-beta-lactams and azido-beta-lactams as acyl-CoA:cholesterol acyltransferase inhibitors

Unprecedented classes of four- and five-membered hydroxyl-spiro-beta-lactams and hydroxyl-azido-beta-lactams were prepared via regioselective ring opening of hydroxyl-epoxides. The potential of these particular beta-lactams as biologically active compounds has been confirmed by the results obtained in ACAT inhibition assays.

And then there were acyl coenzyme A:cholesterol acyl transferase inhibitors

PURPOSE OF REVIEW

The reputation of acyl coenzyme A:cholesterol acyltransferase (ACAT) inhibitors has changed profoundly from promising new drugs for cardiovascular prevention to drugs without clinical benefits or possibly even with adverse effects.

RECENT FINDINGS

ACAT inhibitors decrease the intracellular conversion of free cholesterol into cholesteryl ester in a number of tissues, including intestine, liver and macrophages. In contrast to promising results in experimental animal models, all subsequent clinical studies in humans with ACAT inhibitors failed to show lipid profile changes as well as reductions in surrogate markers for coronary artery disease. In fact, there was even a tendency towards an increase in atheroma burden in the most recent and well executed clinical trials. In addition, the inhibition of this pivotal enzyme in cholesterol esterification may interfere with reverse cholesterol transport.

SUMMARY

In our opinion, the consistent negative findings in recent clinical trials have virtually eliminated the chances for this class of drugs to be introduced for cardiovascular prevention. Possible strategies focused on selective ACAT 2 inhibition or the combination of ACAT inhibitors with compounds that stimulate reverse cholesterol transport may prove to have clinical benefit. This will have to await further clinical research in humans, however, as, obviously, rodent models cannot provide reliable data as to the efficacy of this class of drugs in humans.

Human acyl-CoA:cholesterol acyltransferase (ACAT) and its potential as a target for pharmaceutical intervention against atherosclerosis

Acyl-CoA:cholesterol acyltransferase (ACAT) catalyzes the formation of cholesteryl esters from cholesterol and long-chain fatty-acyl-coenzyme A. At the single-cell level, ACAT serves as a regulator of intracellular cholesterol homeostasis. In addition, ACAT supplies cholesteryl esters for lipoprotein assembly in the liver and small intestine. Under pathological conditions, the accumulation of cholesteryl esters produced by ACAT in macrophages contributes to foam cell formation, a hallmark of the early stage of atherosclerosis. Several reviews addressing various aspects of ACAT and ACAT inhibitors are available. This review briefly outlines the current knowledge on the biochemical properties of human ACATs, and then focuses on discussing the merit of ACAT as a drug target for pharmaceutical interventions against atherosclerosis.

Acyl-CoA: cholesterol acyltransferase inhibitors from Ilex macropoda

Twigs from Ilex macropoda were extracted with MeOH, and the concentrated extracts were partitioned with CH2Cl2, EtOAc, n-BuOH, and H2O. Repeated column chromatography of the CH2Cl2 fraction ultimately resulted in the isolation of two compounds, via activity-guided fractionation, using ACAT inhibitory activity measurements. According to the physico-chemical data, the chemical structures of these isolated compounds were identified as lupeol (1) and betulin (2). Compounds 1 and 2 were shown to inhibit the activity of hACAT-1 and hACAT-2 in a dose-dependent manner, and compounds 1 and 2 inhibited hACAT-1 with IC50 values of 48 and 83 microM, respectively.