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Heritage agrochemicals like myclobutanil, oxyfluorfen, and pronamide, are extensively used in agriculture, with well-established studies on their animal toxicity. Yet, human toxicity assessment relies on conventional human risk assessment approaches including the utilization of animal-based ADME (Absorption, Distribution, Metabolism, and Excretion) data. In recent years, Physiologically Based Pharmacokinetic (PBPK) modelling approaches have played an increasing role in human risk assessment of many chemicals including agrochemicals. This study addresses the absence of PBPK-type data for myclobutanil, oxyfluorfen, and pronamide by generating in vitro data for key input PBPK parameters (Caco-2 permeability, rat plasma binding, rat blood to plasma ratio, and rat liver microsomal half-life), followed by generation of PBPK models for these three chemicals via the GastroPlusTM software. Incorporating these experimental input parameters into PBPK models, the prediction accuracy of plasma AUC (area under curve) was significantly improved. Validation against rat oral administration data demonstrated substantial enhancement. Steady-state plasma concentrations (Css) of pronamide aligned well with published data using measured PBPK parameters. Following validation, parent-based tissue concentrations for these agrochemicals were predicted in humans and rats after single or 30-day repeat exposure of 10 mg/kg/day. These predicted concentrations contribute valuable information for future human toxicity risk assessments of these agrochemicals. [ABSTRACT FROM AUTHOR]

Cholesterol is an essential plasma membrane lipid for the maintenance of cellular homeostasis and cancer cell proliferation. Free cholesterol is harmful to cells; therefore, excessive free cholesterol must be quickly esterified by acetyl‐coenzyme A:cholesterol acetyltransferase (ACAT) and exported by scavenger receptor class B member I (SR‐BI) or ATP‐binding cassette protein A1 from specific cells such as macrophage foam cells, which contain cholesteryl ester‐derived vacuoles. Many vacuoles are present in the cytoplasm of Burkitt lymphoma cells. In this study, we observed that these vacuoles are often seen in high‐grade lymphomas. Cell culture study using lymphoma cell lines found that esterified cholesterol is the main component of these vacuoles and the expression of cholesterol metabolism‐related molecules was significantly upregulated in lymphoma cell lines, with SR‐BI and ACAT inhibitors (BLT‐1 and CI‐976, respectively) impeding lymphoma cell proliferation. Cytoplasmic free cholesterol was increased by ACAT and SR‐BI inhibitors, and the accumulation of free cholesterol induced lymphoma cell apoptosis by inducing endoplasmic reticulum stress. Furthermore, synergistic effects of SR‐BI and ACAT inhibitors were observed in a preclinical study. Treatment with SR‐BI inhibitor suppressed lymphoma progression in a tumor‐bearing mouse model, whereas ACAT inhibitor did not. Therefore, SR‐BI inhibitors are potential new antilymphoma therapeutics that target cholesterol metabolism. [ABSTRACT FROM AUTHOR]

An affordable, stable, reliable and sustainable power supply is the need of the hour, keeping in view the journey to a smart green grid. The present study and derivation of adaptive critical angle threshold (ACAT) contributes to this effect. The ACAT serves as a key index and an indicator to grid operator in proactive mitigation of angular instability in the grid, which is seen to be one of the major initiator of blackouts worldwide. The synchrophasor technology enables accurate calculation of ACAT on real time basis by time synchronised sampling of local voltage and current phasors. The real time calculation makes the index adaptive to variation in system topologies as well as system vulnerabilities. Furthermore, the local system model formed for deriving ACAT has less computational burden while capturing the dynamics of external system, without requirement of intricate power system details. The angular separation of the station bus under supervision can be monitored with respect to the critical angle and serve as a key indicator for initiation of preventive actions during contingencies. The devised methodology is tested using standard IEEE test systems as well as a practical 400/220 kV state grid system using ETAP/MATLAB. [ABSTRACT FROM AUTHOR]

Introduction: Juvenile dermatomyositis (JDM) is the commonest childhood inflammatory myopathy. Outcome of children with JDM has improved significantly with current treatment protocols. We undertook this study to evaluate long‐term outcome of these children using validated outcome measures. Methods: All children diagnosed as JDM and on follow‐up for more than 2 years were eligible for enrolment. Cross‐sectional examination was performed to assess signs of disease activity, damage, physical function and complications by using multiple validated outcome measures/tools. Results: Thirty‐seven patients were enrolled, 19 were male. Median duration of disease at time of enrolment was 73 months (range 24‐219 months) and median duration of follow‐up was 60 months (range 24‐218 months). Disease course was monocyclic in two‐thirds of patients. Eight children were still on therapy at the time of enrolment. On Manual Muscle Testing 8, 3 and 7 children had severe weakness and mild to moderate weakness, respectively. Neck flexors were the most commonly affected muscle group. On abbreviated Cutaneous Assessment Tool, 14 children had evidence of cutaneous activity. More than 50% had at least 1 sign of cutaneous damage, most common signs being calcinosis and lipodystrophy. Nearly two‐thirds of patients had damage in at least 1 organ using Myositis Damage Index. Nine children had physical dysfunction when assessed by Child Health Assessment Questionnaire. Conclusions: Skin disease continued to be active in a significant proportion of patients. Features of damage, namely calcinosis and lipodystrophy, were seen in more than half. Muscle disease normalized in a large proportion of patients. [ABSTRACT FROM AUTHOR]

Niemann‐Pick disease type C (NPC) is a genetic disorder in which patient cells have endosomal/lysosomal accumulation of cholesterol and sphingolipids. However, the relationship between sphingolipids and cholesterol accumulation in NPC cells has not been established. Here, we investigated the role of sphingomyelin (SM) on the accumulation of cholesterol in NPC cells. Reduction of SM by inhibition of the ceramide transfer protein CERT decreased the cholesterol accumulation in NPC cells. The accumulation of SM in NPC cells inhibited the transport of cholesterol to the endoplasmic reticulum. Overexpression of Rab9 in NPC cells reduced the cholesterol accumulation, which was recovered by treatment with SM. In NPC cells that overexpressed a Rab9 constitutively active mutant, SM treatment did not lead to the cholesterol accumulation. These results indicate that SM negatively regulates the Rab9‐dependent vesicular trafficking of cholesterol, and a reduction in SM levels in NPC cells recovers the Rab9‐dependent vesicular trafficking defect. [ABSTRACT FROM AUTHOR]

The ability of Mycobacterium tuberculosis (Mtb) to persist in its human host relies on numerous immune evasion strategies, such as the deregulation of the lipid metabolism leading to the formation of foamy macrophages (FM). Yet, the specific host factors leading to the foamy phenotype of Mtb-infected macrophages remain unknown. Herein, we aimed to address whether host cytokines contribute to FM formation in the context of Mtb infection. Our approach is based on the use of an acellular fraction of tuberculous pleural effusions (TB-PE) as a physiological source of local factors released during Mtb infection. We found that TB-PE induced FM differentiation as observed by the increase in lipid bodies, intracellular cholesterol, and expression of the scavenger receptor CD36, as well as the enzyme acyl CoA:cholesterol acyl transferase (ACAT). Importantly, interleukin-10 (IL-10) depletion from TB-PE prevented the augmentation of all these parameters. Moreover, we observed a positive correlation between the levels of IL-10 and the number of lipid-laden CD14+ cells among the pleural cells in TB patients, demonstrating that FM differentiation occurs within the pleural environment. Downstream of IL-10 signaling, we noticed that the transcription factor signal transducer and activator of transcription 3 was activated by TB-PE, and its chemical inhibition prevented the accumulation of lipid bodies and ACAT expression in macrophages. In terms of the host immune response, TB-PE-treated macrophages displayed immunosuppressive properties and bore higher bacillary loads. Finally, we confirmed our results using bone marrow-derived macrophage from IL-10-/- mice demonstrating that IL-10 deficiency partially prevented foamy phenotype induction after Mtb lipids exposure. In conclusion, our results evidence a role of IL-10 in promoting the differentiation of FM in the context of Mtb infection, contributing to our understanding of how alterations of the host metabolic factors may favor pathogen persistence. [ABSTRACT FROM AUTHOR]

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Three series of xanthone sulfonamides were synthesized, and their inhibitory activities against acyl-CoA: cholesterol acyltransferase (ACAT) were evaluated. Results showed that most of the title compounds exhibited strong inhibitory activity against ACAT, of which compounds 1c, 1e, 1f, 2d, 2e, and 3d were proved to be more active than the positive control Sandoz 58-035. Computational docking experiments indicated that the interaction between inhibitors and ACAT contained the H-bond interaction, the hydrophobic interaction, and the narrow hydrophobic cleft. [ABSTRACT FROM AUTHOR]

Acyl-CoA:cholesterol acyltransferase 1 (ACAT1) is a resident endoplasmic reticulum enzyme that prevents the buildup of cholesterol in membranes by converting it to cholesterol esters. Blocking ACAT1 pharmacologically or by Acatl gene knock-out (KO) decreases amyloidopathy in mouse models for Alzheimer's disease. However, the beneficial actions of ACAT1 blockage to treat Alzheimer's disease remained not well understood. Microglia play essential roles in the proteolytic clearance of amyloid β (Aβ) peptides. Here we show that Acatl gene KO in mouse increases phagocytic uptake of oligomeric Aβl-42 and stimulates lysosomal Aβl-42 degradation in cultured microglia and in vivo. Additional results show that Acatl gene KO or a specific ACAT1 inhibitor K604 stimulates autophagosome formation and transcription factor EB-mediated lysosomal proteolysis. Surprisingly, the effect of ACAT1 blockage does not alter mTOR signaling or endoplasmic reticulum stress response but can be modulated by agents that disrupt cholesterol biosynthesis. To our knowledge, our current study provides the first example that a small molecule (K604) can promote autophagy in an mTOR-independent manner to activate the coordinated lysosomal expression and regulation network. Autophagy is needed to degrade misfolded proteins/ peptides. Our results implicate that blocking ACAT1 may provide a new way to benefit multiple neurodegenerative diseases. [ABSTRACT FROM AUTHOR]

ABSTRACT Cholesteryl oleate present as a neutral lipid in low-density lipoprotein has been speculated to be a biomarker for atherosclerosis. Methods which are at hand for the quantification of cholesteryl oleate are either costly or entail the use of radioactive compounds. Charring of TLC plates has been used to identify cholesteryl esters for a long time but has never been applied to quantification of cholesteryl esters in biological matrices. Here, we report a novel method based on planar chromatography for the analysis of the products of the acyl CoA-cholesterol acyltransferase (ACAT) assay, viz. cholesteryl esters. Using silica gel 60 F254 as stationary phase, compounds were spotted on the plate and run using a solvent system comprising n-hexane-diethyl ether-glacial acetic acid (90:10:1, v/v/v). The plates were developed by dipping in anisaldehyde-sulfuric acid reagent and were scanned at 546 nm for quantification. The developed method shows good linear relationship in the concentration range of 100-500 ng/band with a correlation coefficient ( r) value of 0.9996. The method was validated for accuracy, precision and robustness. Percentage recovery of the method was found to be in the range 96.88-103.01% with intra- and inter-day precision analysis yielding <2% relative standard deviation at nominal concentrations for analysis. The limits of detection and quantification were found to be 6.45 and 19.54 ng, respectively. The method was validated for robustness by making deliberate changes in mobile phase composition, volume and temperature of analysis, and the standard deviations of peak areas for these intentional changes were found to be 1.07, 1.02 and 1.30 respectively. The method was applied to the estimation of cholesteryl esters in plasma samples from patients diagnosed with hypercholesterolemia. No interferences were found from the biological matrices used in the assay. The proposed method could be of immense potential for estimation of cholesteryl oleate as a marker of ACAT activity, for screening of ACAT inhibitors in drug discovery process and in the prognosis of atherosclerosis. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Sublingual administration of certain buffered propranolol may improve the rate and extent of absorption compared to oral administration. The main objectives of this study were to (1) compare the plasma propranolol concentrations (Cp-prop) following sublingual administration of a specially buffered formulation (Promptol™) to that following oral administration of Inderal and (2) evaluate the utility of a special pharmacokinetic model in describing the Cp-prop following sublingual administration. Eighteen healthy volunteers received 10 mg sublingual Promptol™ or oral Inderal. Multiple Cp-prop were determined and their pharmacokinetics compared. Additional data following sublingual 40 mg Promptol™ or Inderal were utilized for evaluation of a special advanced compartmental absorption and transit (ACAT) model. For model simulation, the physicochemical parameters were imported from AMET predictor, whereas the pharmacokinetic parameters were calculated and optimized by Gastroplus. Based on this model, the quantity of drug absorbed via buccal/sublingual mucosa was estimated. Cp-prop was higher at earlier times with 3-fold greater relative bioavailability following sublingual Promptol™ compared to that from oral Inderal. The special ACAT model provided excellent goodness of fit of Cp-prop-time curve and estimated a 56.6% increase in absorption rate from Promptol™ and higher initial Cp-prop compared to the regular formulation. The modified ACAT model provided a useful approach to describe sublingual absorption of propranolol and clearly demonstrated an improvement of absorption of Promptol™. The sublingual 10 mg Promptol™ achieved not only a similar systemic exposure as 30 mg oral Inderal but an earlier effective Cp-prop which may be advantageous for certain clinical conditions. [ABSTRACT FROM AUTHOR]

ABSTRACT Schnyder corneal dystrophy ( SCD) is an autosomal dominant disease characterized by germline variants in UBIAD1 introducing missense alterations leading to deposition of cholesterol in the cornea, progressive opacification, and loss of visual acuity. UBIAD1 was recently shown to synthesize menaquinone-4 ( MK-4, vitamin K2), but causal mechanisms of SCD are unknown. We report a novel c.864G>A UBIAD1 mutation altering glycine 177 to glutamic acid (p.G177E) in six SCD families, including four families from Finland who share a likely founder mutation. We observed reduced MK-4 synthesis by UBIAD1 altered by SCD mutations p.N102S, p.G177R/E, and p.D112N, and molecular models showed p.G177-mutant UBIAD1 disrupted transmembrane helices and active site residues. We show UBIAD1 interacts with HMGCR and SOAT1, enzymes catalyzing cholesterol synthesis and storage, respectively, using yeast two-hybrid screening and immunoprecipitation. Docking simulations indicate cholesterol binds to UBIAD1 in the substrate-binding cleft and substrate-binding overlaps with GGPP binding, an MK-4 substrate, suggesting potential competition between these metabolites. Impaired MK-4 synthesis is a biochemical defect identified in SCD suggesting UBIAD1 links vitamin K and cholesterol metabolism through physical contact between enzymes and metabolites. Our data suggest a role for endogenous MK-4 in maintaining cornea health and visual acuity. [ABSTRACT FROM AUTHOR]

Hyperlipidemia is an important factor to induce metabolic syndrome such as obesity, diabetes and cardiovascular diseases. Recently, some antihyperlipidemic agents from herbal medicines have been in the spotlight in the medical science field. Thus, the present study evaluated the antihyperlipidemic activities of the essential oil from the leaves of Pinus koraiensis SIEB (EOPK) that has been used as a folk remedy for heart disease. The reverse transcription polymerase chain reaction (RT-PCR) revealed that EOPK up-regulated low density lipoprotein receptor (LDLR) at the mRNA level as well as negatively suppressed the expression of sterol regulatory element-binding protein (SREBP)-1c, SREBP-2, 3-hydroxy-3-methyl-glutaryl-CoA reductase (HMGCR), fatty acid synthase (FAS) and glycerol-3-phosphate acyltransferase (GPAT) involved in lipid metabolism in HepG2 cells. Also, western blotting showed that EOPK activated LDLR and attenuated the expression of FAS at the protein level in the cells. Consistently, EOPK significantly inhibited the level of human acylcoenzyme A: cholesterol acyltransferase (hACAT)1 and 2 and reduced the low-density lipoprotein (LDL) oxidation activity. Furthermore, chromatography-mass spectrometry (GC-MS) analysis showed that EOPK, an essential oil mixture, contained camphene (21.11%), d-limonene (21.01%), α-pinene (16.74%) and borneol (11.52%). Overall, the findings suggest that EOPK can be a potent pharmaceutical agent for the prevention and treatment of hyperlipidemia. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Purpose: To introduce guidelines in selecting the particle size distribution ( n0, cm−1) that will guarantee optimal oral absorption for drugs with low solubility. Methods: Unlike other multi-compartmental models the gastrointestinal tract is modeled as a continuous tube with spatially varying properties. The transport through the intestinal lumen is described using the dispersion model. The model accounts for the dissolution of poly-dispersed powders. Results: The model was used to examine the sensitivity of the absorption on permeability (P) and water solubility (Cs) following administration in different log-normal powders. The absorption exhibits inverse sigmoidal dependence on the mean particle size (rm, µm) regardless of the administrated dose or drug properties. Thus, there is an optimal rm that maximizes the benefit-cost ratio of the formulation; finer particles do not improve the absorption while coarser particles decrease it. Using the model we find that the optimal rm depends mainly on the drug Cs and on the geometrical standard deviation (gSTD). Conclusions: The results of this work provide the formulator with guidelines to select both rm and gSTD that guarantee optimal absorption. [ABSTRACT FROM AUTHOR]

Novel synthetic oxysterols (22S,23S)-3β-hydroxy-22,23-oxido-5α-ergost-8(14)-en-15-one ( I) and (22R,23R)-3β-hydroxy-22,23-oxido-5α-ergost-8(14)-en-15-one ( II) influenced biosynthesis of cholesteryl esters from [14C]acetate (85% and 180% of control at 5 μM concentration) in the human hepatoma Hep G2 cell line. Ketosterol ( I) increased the level of cholesteryl ester biosynthesis from [14C]oleate in Hep G2 cells in a dose dependent manner, whereas the level of cholesteryl esters biosynthesis in the presence of ketosterol ( II) reached the maximal value (269±20% of control) at 1 μM concentration of this compound. In a cell free system ketosterol ( I) increased the rate of ACAT-dependent cholesterol acylation similar to 25-hydroxycholesterol, however, ketosterol ( II)), efficiently stimulated an initial rate of ACAT-catalyzed cholesterol esterification, followed by rapid inactivation of this enzyme. [ABSTRACT FROM AUTHOR]

Growing evidence suggests that the small intestine may contribute to excessive postprandial lipemia, which is highly prevalent in insulin-resistantl Type 2 diabetic individuals and substantially increases the risk of cardiovascular disease. The aim of the present study was to determine the role of high glucose levels on intestinal cholesterol absorption, cholesterol transporter expression, enzymes controlling cholesterol homeostasis, and the status of transcription factors. To this end, we employed highly differentiated and polarized cells (20 days of culture), plated on permeable polycarbonate filters. In the presence of [[sup14]C]cholesterol, glucose at 25 mM stimulated cholesterol uptake compared with Caco-2/15 cells supplemented with 5 mM glucose (P < 0.04). Because combination of 5 mM glucose with 20mM of the structurally related mannitol or sorbitol did not change cholesterol uptake, we conclude that extracellular glucose concentration is uniquely involved in the regulation of intestinal cholesterol transport. The high concentration of glucose enhanced the protein expression of the critical cholesterol transporter NPC1L1 and that of CD36 (P < 0.02) and concomitantly decreased SR-BI protein mass (P < 0.02). No significant changes were observed in the protein expression of ABCA1 and ABCG8, which act as efflux pumps favoring cholesterol export out of absorptive cells. At the same time, 3-hydroxy-3-methylglutaryl-coenzyme A reductase activity was decreased (P < 0.007), whereas ACAT activity remained unchanged. Finally, increases were noted in the transcription factors LXR-α, LXR-β, PPAR-β, and PPAR--γ along with a drop in the protein expression of SREBP-2. Collectively, our data indicate that glucose at high concentrations may regulate intestinal cholesterol transport and metabolism in Caco-2/15 cells, thus suggesting a potential influence on the cholesterol absorption process in Type 2 diabetes. [ABSTRACT FROM AUTHOR]

Abstract: Previous studies have shown that acyl-coenzyme A:cholesterol acyl transferase (ACAT), an enzyme that controls cellular equilibrium between free cholesterol and cholesteryl esters, modulates proteolytic processing of APP in cell-based and animal models of Alzheimer’s disease. Here we report that ACAT-1 RNAi reduced cellular ACAT-1 protein by ∼50% and cholesteryl ester levels by 22% while causing a slight increase in the free cholesterol content of ER membranes. This correlated with reduced proteolytic processing of APP and 40% decrease in Aβ secretion. These data show that even a modest decrease in ACAT activity can have robust suppressive effects on Aβ generation. [Copyright &y& Elsevier]

Esterification of sterols, fatty acids and other alcohols into biologically inert forms conserves lipid resources for many cellular functions. Paradoxically, the accumulation of neutral lipids such as cholesteryl ester or triglyceride, is linked to several major disease pathologies. In a remarkable example of genetic expansion, there are at least eleven acyltransferase reactions that lead to neutral lipid production. In this review, we speculate that the complexity and apparent redundancy of neutral lipid synthesis may actually hasten rather than impede the development of novel, isoform-specific, therapeutic interventions for acne, type 2 diabetes, obesity, hyperlipidemia, fatty liver disease, and atherosclerosis. [ABSTRACT FROM AUTHOR]

Ixeris dentata forma albiflora was extracted with 80% aqueous MeOH, and the concentrated extract was partitioned with EtOAc, n-BuOH and H2O. Eight sesquiterpenes were isolated through repeated silica gel and octadecyl silica gel (C18, ODS) column chromatography of the EtOAc and n-BuOH fractions. Physicochemical analysis using NMR, MS and IR revealed the chemical structures of the sesquiterpenes, which were zaluzanin ( 1), 9a-hydroxyguaian-4(15), 10(14), 11(13)-triene-6, 12-olide ( 2), 3β-O-β-D-glucopyranosyl-8β-hydroxyguaian-4(15), 10(14)-diene-6,12-olide ( 3), 3-O-β-D-glucopyranosyl-8β-hydroxyguauan-10(14)-ene-6,12-olide ( 4), ixerin M (5), glucozaluzanin C ( 6), crepiside I ( 7), and ixerin D ( 8). This is the first time that these sesquiterpene lactones have been isolated from this plant. Compounds 1, 2 and 7 revealed relatively high cytotoxicities on human colon carcinoma cell and lung adenocarcinoma cell, while compounds 5 and 7 showed acyl-CoA: cholesterol acyltransferase (ACAT) inhibitory activity. [ABSTRACT FROM AUTHOR]

ABSTRACT Guinea pigs are useful models to investigate the mechanisms of the hypocholesterolemic effects of drugs. Like humans, guinea pigs are one of the few species that carry the majority of cholesterol in LDL. This animal model has also been shown to develop atherosclerosis when challenged with hypercholesterolemic diets. In addition, plasma lipid profiles in males, females and ovariectomized guinea pigs, a model for menopause, follow similar patterns to those observed in humans. In this report, drugs aimed at lowering plasma cholesterol and triglycerides in hyperlipidemic individuals are reviewed. Studies analyzing the hypolipidemic effect of HMG-CoA reductase inhibitors, acyl CoA cholesterol acyltransferase inhibitors, fibrates, bile acid resins, apical sodium bile acid transporter inhibitors, and others show that guinea pigs and humans have comparable responses to drug therapy. In addition, results from the limited clinical reports addressing specific effects of drugs on LDL catabolism or VLDL synthesis are in agreement with observations in guinea pigs. From the review of these studies, it is apparent that the guinea pig is a useful animal model to further explore the mechanisms of action of lipid lowering drugs including effects on specific receptors and regulatory enzymes involved in cholesterol metabolism and on early atherosclerosis development. [ABSTRACT FROM AUTHOR]

: Cholesterol esterification and smooth muscle cell (SMC) proliferation are the crucial events in the development of atherosclerotic lesions. The objective of this study was to analyse cholesterol esterification and the expression of MDR1 (multidrug resistance), ACAT (acyl-CoA:cholesterol acyltransferase) and caveolin-1 genes in atherosclerotic and healthy vascular walls, in SMCs obtained from atherosclerotic lesions and saphenous veins. Results demonstrated higher levels of cholesterol esters, ACAT and MDR1 mRNAs and lower levels of caveolin-1 mRNA in atherosclerotic segments compared to adjacent serial sections of the same artery and the corresponding non-atherosclerotic arteries from cadaveric donors. SMCs isolated from atherosclerotic plaques manifested an increased capacity to esterify cholesterol and to grow at a faster rate than SMCs isolated from saphenous veins. In addition, when SMCs from atherosclerotic plaques were cultured in the presence of progesterone, a potent inhibitor of cholesterol esterification, significant growth suppression was observed. An increase in ACAT and MDR1 expression and a concomitant decrease in caveolin-1 expression were also observed in SMCs isolated from atherosclerotic arteries as early as 12 h after serum stimulation. An opposite pattern was found when SMCs were treated with progesterone. These findings support the idea that cholesterol esterification plays a role both in early atherogenesis and in clinical progression of advanced lesions and raise the possibility that the cholesterol ester pathway might directly modulate the proliferation of SMCs. [ABSTRACT FROM AUTHOR]

The initial rate of14C-cholesterol uptake from mixed micelles is studied using organ culture of mucosal epithelium from human small intestine obtained during surgery. Intense, reproducible, and ACAT-regulated level of specific14C-cholesterol uptake is monitored during the first 3 h of culturing. The specific14C-cholesterol uptake is assessed by the difference between the total uptake of14C-cholesterol and nonspecific uptake of14C-sitosterol from the micelles. It is shown that less than 20% of absorbed14C-cholesterol is converted into cholesterol esters. C44788, a high-affinity and selective ACAT inhibitor, inhibits14C-cholesterol uptake in a dose-dependent manner and practically has no effect on14C-oleate uptake. [ABSTRACT FROM AUTHOR]

We have studied the correlation between changes in the lipid composition in chick liver microsomes and the activities of 3-hydroxy-3-methylglutaryl-CoA reductase (HMG-CoA reductase) and acyl-CoA : cholesterol acyltransferase (ACAT) by in vivo and in vitro experiments with 21-day-old chicks. A 5% cholesterol diet for 3 hr produced an increase in the microsomal and plasmatic cholesterol content, a decrease in HMG-CoA reductase activity and a concomitant increase in ACAT activity. The effect produced by the short-term treatment virtually disappeared 27 hr after ending the cholesterol diet. In vitro experiments were carried out by using vesicles constituted by phosphatidycholine/cholesterol and phosphatidylcholine. [ABSTRACT FROM AUTHOR]

Accumulation of cholesterol and calcium is the hallmark of atherosclerosis. Ca2+ antagonists lessen the severity of experimentally induced atherosclerosis in a variety of animal models, including hypercholesterolaemic animals. They also reduce cholesterol accumulation in the arterial wall, but without affecting plasma lipids. This review briefly discusses in vitro and in vivo experimental studies on the anti-atherosclerotic properties of Ca2+ antagonists and outlines mechanisms by which these compounds affect cellular lipid metabolism. [ABSTRACT FROM PUBLISHER]

The purification and cloning of the acyl-coenzyme A: cholesterol acyltransferase (ACAT) enzymes and the sterol O-acyltransferase (SOAT) genes has opened new areas of interest in cholesterol metabolism given their profound effects on foam cell biology and intestinal lipid absorption. The generation of mouse models deficient in Soat1 or Soat2 confirmed the importance of their gene products on cholesterol esterification and lipoprotein physiology. Although these studies supported clinical trials which used non-selective ACAT inhibitors, these trials did not report benefits, and one showed an increased risk. Early genetic studies have implicated common variants in both genes with human traits, including lipoprotein levels, coronary artery disease, and Alzheimer's disease; however, modern genome-wide association studies have not replicated these associations. In contrast, the common SOAT1 variants are most reproducibly associated with testosterone levels. [ABSTRACT FROM AUTHOR]

This study was concerned with the effect of insulin and catecholamines on the rate limiting enzymes of cholesterol metabolism in rat hepatocytes. Insulin was found to increase the activity of 3-hydroxy-3-methyl glutaryl coenzyme A reductase and to have no effect on the activity of acyl-coenzyme A: cholesterol-o-acyltransferase. Noradrenaline and isoprenaline increased the activities of both 3-hydroxy3-methyl glutaryl coenzyme A reductase and acyl-coenzyme A: cholesterol-o-acyltransferase. The effect of noradrenaline or isoprenaline in the presence of insulin was that of a lower stimulatory response on 3-hydroxy-3-methyl glutaryl coenzyme A reductase but comparable to that found with either catecholamine alone. The combination of either catecholamine with insulin had no effect on the activity of acyl-coenzyme A: cholesterol-o-acyltransferase. These observations suggest that the activities of 3-hydroxy-3-methyl glutaryl coenzyme A reductase and acyl-coenzyme A: cholesterol-o-acyltransferase are regulated independently by insulin in the presence or absence of catecholamines. By contrast, catecholamines appear to regulate both enzyme activities in a similar fashion. [ABSTRACT FROM AUTHOR]

The macrophage plays a diverse array of roles in atherogenesis and lipoprotein metabolism. The macrophage functions as a scavenger cell, an immune mediator cell, and as a source of chemotactic molecules and cytokines. Chemokines have been implicated in promoting migration of monocytes into the arterial intima. Monocyte chemoattractant protein-1 (MCP-1) attracts monocytes bearing the chemokine receptor CCR-2. Macrophage expression of cyclooxygenase-2, a key enzyme in inflammation, promotes atherosclerotic lesion formation in low-density lipoprotein receptor (LDLR)-deficient mice. In the arterial intima, monocytes differentiate into macrophages, which accumulate cholesterol esters to form lipid-laden foam cells. Foam cell formation can be viewed as an imbalance in cholesterol homeostasis. The uptake of atherogenic lipoproteins is mediated by scavenger receptors, including SR-A and CD36. In the macrophage, ACAT-1 is responsible for esterifying free cholesterol with fatty acids to form cholesterol esters. Surprisingly, deficiency of macrophage ACAT-1 promotes atherosclerosis in LDLR-deficient mice. A number of proteins have been implicated in the process of promoting the efflux of free cholesterol from the macrophage, including apoE, ABCA1, and SRB-1. Macrophage-derived foam cells express the adipocyte fatty acid-binding protein (FABP), aP2, a cytoplasmic FABP that plays an important role in regulating systemic insulin resistance in the setting of obesity. ApoE-deficient mice null for macrophage aP2 expression develop significantly less atherosclerosis than controls wild type for macrophage aP2 expression. These results demonstrate a significant role for macrophage aP2 in the formation of atherosclerotic lesions independent of its role in systemic glucose and lipid metabolism. Furthermore, macrophages deficient in aP2 display alterations in inflammatory cytokine production. Through its distinct actions in adipocytes and macrophages, aP2 links features of the metabolic syndrome including insulin resistance, obesity, inflammation, and atherosclerosis.International Journal of Obesity (2003) 27, S35-S40. doi:10.1038/sj.ijo.0802498 [ABSTRACT FROM AUTHOR]

The influence of bezafibrate treatment on hepatic cholesterol metabolism was studied in rats and in humans. The activities of the three key enzymes involved in cholesterol metabolism [3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase, cholesterol 7 α-hydroxylase, and acyl-coenzyme A: cholesterol acyltransferase (ACAT)] were suppressed by bezafibrate treatment in rats, but only the ACAT activity was significantly decreased when the activity was related to total liver weight. In humans, HMG-CoA reductase activity was increased about twice in the treated normolipidemic gallstone patients. In contrast, the concentration of lathosterol in serum decreased, indicating depression of the cholesterol synthesis. The increase in HMG-CoA reductase activity may be a compensatory effect of an inhibition of some other enzymes in the synthesis of cholesterol, as in vitro study on liver microsomes excluded a direct inhibitory effect of bezafibrate on HMG-CoA reductase. The ACAT activity was not significantly changed, and the cholesterol 7 a-hydroxylase activity was decreased by 55-60% compared with controls. The LDL-receptor-binding activity was unaffected by bezafibrate treatment. [ABSTRACT FROM AUTHOR]

The influence of bezafibrate treatment on hepatic cholesterol metabolism was studied in rats and in humans. The activities of the three key enzymes involved in cholesterol metabolism [3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase, cholesterol 7 α-hydroxylase, and acyl-coenzyme A: cholesterol acyltransferase (ACAT)] were suppressed by bezafibrate treatment in rats, but only the ACAT activity was significantly decreased when the activity was related to total liver weight. In humans, HMG-CoA reductase activity was increased about twice in the treated normolipidemic gallstone patients. In contrast, the concentration of lathosterol in serum decreased, indicating depression of the cholesterol synthesis. The increase in HMG-CoA reductase activity may be a compensatory effect of an inhibition of some other enzymes in the synthesis of cholesterol, as in vitro study on liver microsomes excluded a direct inhibitory effect of bezafibrate on HMG-CoA reductase. The ACAT activity was not significantly changed, and the cholesterol 7 α-hydroxylase activity was decreased by 55-60% compared with controls. The LDL-receptor-binding activity was unaffected by bezafibrate treatment. [ABSTRACT FROM AUTHOR]