51
|
Aragane K, Kusunoki J, Kitamine T, Yamaura T, Ohnishi H. Effects of F-1394, an acyl-CoA:cholesterol acyltransferase (ACAT) inhibitor, on ACAT activity in HepG2 cells and on hepatic secretion of lipids in Triton WR-1339-induced hyperlipidemic rats: possible role of hepatic ACAT in very low density lipoprotein secretion. JAPANESE JOURNAL OF PHARMACOLOGY 1998; 76:309-12. [PMID: 9593225 DOI: 10.1254/jjp.76.309] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
We examined the inhibitory potency of F-1394 ((1S,2S)-2-[3-(2,2-dimethylpropyl)-3-nonylureido]cyclohexane -1-yl 3-[(4R)-N-(2,2,5,5-tetramethyl-1,3-dioxane-4-carbonyl)amino]propionate), an acyl-CoA:cholesterol acyltransferase (ACAT) inhibitor, on ACAT activity and its hypolipidemic effect. F-1394 inhibited whole-cell ACAT activity in HepG2 cells with an IC50 value of 42 nM. The potency of F-1394 was greater than that of the five other ACAT inhibitors tested (YM-17E, CI-976, 57-118, CL-277,082 and DL-melinamide). In rats made hyperlipidemic by Triton WR-1339, F-1394 caused a reduction in the hepatic secretion rate of cholesterol. These data suggest that inhibition of hepatic ACAT activity helps to reduce very low density lipoprotein secretion from the liver into the circulation.
Collapse
Affiliation(s)
- K Aragane
- Pharmaceuticals Research Laboratories, Fujirebio, Inc., Hachioji, Tokyo, Japan
| | | | | | | | | |
Collapse
|
52
|
Ellsworth JL, Starr JR. Inhibition of acyl coenzyme A:cholesterol acyltransferase blocks esterification but not uptake of cholesterol in Caco-2 cells. Metabolism 1998; 47:325-32. [PMID: 9500571 DOI: 10.1016/s0026-0495(98)90265-7] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The effects of cholesterol esterase (CEase) and acyl coenzyme A:cholesterol acyltransferase (ACAT) inhibitors on the uptake and esterification of cholesterol in Caco-2 cells were examined. CEase increased the uptake of [3H]cholesterol from bile salt mixed-micelles by 2.5- to 3.0-fold and its esterification by greater than 25-fold. Inhibition of cellular ACAT activity with CL277082 or CP113818 had little or no effect on cholesterol uptake measured in the presence or absence of CEase. The subsequent esterification of [3H]cholesterol was reduced greater than 90% by each ACAT inhibitor. Similar results were obtained in cells in which ACAT activity was induced by preincubation either with 25-hydroxycholesterol and mevalonic acid or with CEase and bile salt mixed-micelles containing 100 micromol/L cholesterol. Neither ACAT inhibitor had an effect on CEase-mediated synthesis or hydrolysis of cholesteryl oleate in vitro. Thus, the uptake of cholesterol from bile salt mixed-micelles in the presence or absence of CEase was not regulated by the level of cellular ACAT expression. The subsequent esterification of exogenous sterol was not due to CEase, but was completely dependent on ACAT activity. The dissociation of cholesterol uptake from ACAT activity suggests that the factors controlling the transfer of sterol from extracellular media to the cell are different from the factors regulating the cellular level of cholesterol esterification.
Collapse
|
53
|
Uchida T, Aoyama K, Watanabe T, Higuchi S. Relationship between bioavailability and hypocholesterolemic activity of YM17E, an inhibitor of ACAT, in cholesterol-fed rats. Atherosclerosis 1998; 137:97-106. [PMID: 9568741 DOI: 10.1016/s0021-9150(97)00259-1] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The relationship between bioavailability and the serum cholesterol-lowering effect of YM17E, an ACAT inhibitor was investigated. Serum cholesterol levels in cholesterol-fed rats decreased after both oral and intravenous administration of YM17E. Marked inhibition of cholesterol absorption was observed after oral administration, but not after intravenous administration. YM17E and its five active metabolites were primarily distributed in the liver after intravenous administration, but in small intestine and liver after oral administration. Hepatic ACAT activity in cholesterol-fed rats was inhibited by intravenous administration. Cholesteryl ester input into plasma by Triton WR-1339 treatment to the rats was inhibited by intravenous administration of YM17E. Plasma clearance of 125I-LDL in cholesterol-fed rats increased after YM17E treatment suggesting a decrease in LDL production. These results indicate that the hypocholesterolemic effect of intravenous YM17E was due to hepatic ACAT inhibition, not an inhibition of intestinal cholesterol absorption. The contribution of ACAT inhibition in small intestine and liver on the pharmacological effect could be explained by plasma inhibitor concentration after oral or intravenous administration of YM17E. From these results, it is concluded that the change in bioavailability of ACAT inhibitors change the mechanism of hypocholesterolemic effects, shifting the relative contributions of small intestinal and hepatic ACAT inhibition.
Collapse
Affiliation(s)
- T Uchida
- Drug Metabolism Laboratories, Yamanouchi Pharmaceutical Co., Tokyo, Japan
| | | | | | | |
Collapse
|
54
|
Tanaka A, Terasawa T, Hagihara H, Kinoshita T, Sakuma Y, Ishibe N, Sawada M, Takasugi H, Tanaka H. Synthesis, X-ray crystal structure, and biological activity of FR186054, a novel, potent, orally active inhibitor of acyl-CoA:cholesterol O-acyltransferase (ACAT) bearing a pyrazole ring. Bioorg Med Chem Lett 1998; 8:81-6. [PMID: 9871633 DOI: 10.1016/s0960-894x(97)10191-3] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The synthesis, single crystal X-ray structural analysis, and biological activity of FR186054 (2c), a new, potent, orally efficacious inhibitor of acyl-CoA:cholesterol O-acyltransferase (ACAT), containing a pyrazole ring are described. This compound displayed excellent in vitro efficacy, irrespective of dosing method, indicating superior characteristics compared to other ACAT inhibitors.
Collapse
Affiliation(s)
- A Tanaka
- Medicinal Chemistry Research Laboratories, Fujisawa Pharmaceutical Co. Ltd., Osaka, Japan
| | | | | | | | | | | | | | | | | |
Collapse
|
55
|
Tanaka A, Terasawa T, Hagihara H, Sakuma Y, Ishibe N, Sawada M, Takasugi H, Tanaka H. Inhibitors of acyl-CoA:cholesterol O-acyltransferase (ACAT). Part 1: identification and structure-activity relationships of a novel series of substituted N-alkyl-N-biphenylylmethyl-N'-arylureas. Bioorg Med Chem 1998; 6:15-30. [PMID: 9502102 DOI: 10.1016/s0968-0896(97)10009-8] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
A series of N-alkyl-N-biphenylylmethyl-N'-arylurea and related derivatives represented by 1 have been prepared and evaluated for their ability to inhibit acyl-CoA:cholesterol O-acyltransferase in vitro and to lower plasma cholesterol levels in cholesterol-fed rats in vivo. Linking of two phenyl groups via oxygen and introduction of fluorine at appropriate positions on the biphenyl moiety improved in vitro and in vivo activity. From this series of analogs, compound 40 (FR179254), which had potent in vitro potency (rabbit intestinal microsomes IC50 = 25 nM), showed excellent plasma cholesterol-lowering activity when administered via the diet (ED50 = 0.045 mg/kg). However, the hypocholesterolemic effect of this compound was moderate when dosed by oral gavage in PEG400 as a vehicle (ED50 = 5.3 mg/kg). Modification of the N'-aryl moiety led to the identification of compound 50 (FR182980) which was efficacious in both dosing models (ED50 = 0.034 mg/kg and 0.11 mg/kg, respectively).
Collapse
Affiliation(s)
- A Tanaka
- Medicinal Chemistry Research Laboratories, Fujisawa Pharmaceutical Co. Ltd., Osaka, Japan
| | | | | | | | | | | | | | | |
Collapse
|
56
|
Roth BD. ACAT inhibitors: evolution from cholesterol-absorption inhibitors to antiatherosclerotic agents. Drug Discov Today 1998. [DOI: 10.1016/s1359-6446(97)01123-9] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
|
57
|
Murakami S, Yamagishi I, Sato M, Tomisawa K, Nara Y, Yamori Y. ACAT inhibitor HL-004 accelerates the regression of hypercholesterolemia in stroke-prone spontaneously hypertensive rats (SHRSP): stimulation of bile acid production by HL-004. Atherosclerosis 1997; 133:97-104. [PMID: 9258412 DOI: 10.1016/s0021-9150(97)00121-4] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The effect of the acyl-CoA:cholesterol acyltransferase (ACAT) inhibitor HL-004 on bile acid production was studied during the regression phase of pre-established hypercholesterolemia in stroke-prone spontaneously hypertensive rats (SHRSP). These rats were fed a hypercholesterolemic diet containing 5% cholesterol, 2% cholic acid, and 20% suet for 30 days to induce hypercholesterolemia. The regression phase was started by switching the diet to normal chow, followed by another 30 days of the diet. The decrease in serum cholesterol level was accelerated by treatment with 0.09% HL-004. At the end of regression, hepatic ACAT activity was significantly lower in the HL-004 treated animals, an event concomitant with the significant decrease in cholesteryl ester content in the liver. In contrast hepatic cholesterol 7 alpha-hydroxylase activity was maintained at a higher level in the HL-004 treated animals. HL-004 increased the secretion of bile acid and biliary lipids in bile duct-cannulated SHRSP. In HepG2:cells, HL-004 at 1-30 microM dose-dependently stimulated bile acid synthesis from [3H]cholesterol. When cholesterol 7 alpha-hydroxylase activity of the liver was compared ex vivo in the presence and in the absence of exogenous cholesterol, it was suggested that the higher 7 alpha-hydroxylase activity of the HL-004 group could be attributed not only to expansion of the endogenous cholesterol pool, which may be the result of hepatic ACAT inhibition by HL-004 but to the direct effect of HL-004 on bile acid production. Thus, HL-004 accelerates the regression of hypercholesterolemia, an event which may be related to the stimulation of bile acid production in the liver.
Collapse
Affiliation(s)
- S Murakami
- Medicinal Research Laboratories, Taisho Pharmaceutical Co. Ltd., Ohmiya, Japan.
| | | | | | | | | | | |
Collapse
|
58
|
Li HY, DeLucca I, Boswell GA, Billheimer JT, Drummond S, Gillies PJ, Robinson C. Design, synthesis and structure-activity relationship studies of novel 4,4-bis(trifluoromethyl)imidazolines as acyl-CoA: cholesterol acyltransferase (ACAT) inhibitors and antihypercholesterolemic agents. Bioorg Med Chem 1997; 5:1345-61. [PMID: 9377095 DOI: 10.1016/s0968-0896(97)00058-8] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Novel 4,4-bis(trifluoromethyl)imidazolines have been found to be the potent acyl-CoA cholesterol acyltransferase (ACAT) inhibitors. ACAT is responsible for cholesterol esterification in the intestine, liver, and the arterial wall. These novel imidazolines also inhibit cholesterol ester formation in the macrophage. Several compounds have shown potent serum cholesterol-lowering activity in several animal models. Para-substitution of the 2-phenyl is critical for in vitro and in vivo activity. The 4,4-bis(trifluoromethyl)imidazolines with a para-cyano group on 2-phenyl and a 4-alkylcyclohexyl amide as the side-chain at the 5-position possess the most potent inhibitory activity in this series. Based on biochemical studies, this series acts as a competitive inhibitor with respect to cholesterol binding at the enzyme, which distinguishes it from most of the ACAT inhibitors discovered to date. Preliminary biological studies supported by X-ray crystal structures, molecular modeling, and structure-activity relationship (SAR) studies suggest that this series may be a cholesterol mimic.
Collapse
Affiliation(s)
- H Y Li
- The DuPont Merck Pharmaceutical Company, Experimental Station, Wilmington, DE 19880-0500, U.S.A.
| | | | | | | | | | | | | |
Collapse
|
59
|
Purchase TS, Essenburg AD, Hamelehle KL, Hes MS, Holmes A, Krause BR, Stanfield RL, Trivedi BK. Inhibitors of acyl-CoA:cholesterol acyltransferase: novel trisubstituted ureas as hypocholesterolemic agents. Bioorg Med Chem 1997; 5:739-47. [PMID: 9158873 DOI: 10.1016/s0968-0896(97)00019-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Our continued interest in developing novel, potent acyl-CoA:cholesterol acyltransferase (ACAT) inhibitors, and our discovery of several active series of disubstituted urea ACAT inhibitors, have led us to investigate a series of trisubstituted ureas that are structural hybrids of our disubstituted series and of a trisubstituted urea ACAT inhibitor series disclosed by scientists at Lederle. This investigation has led to the discovery of novel trisubstituted ureas, several of which inhibit ACAT in the nanomolar range and effectively lower total plasma cholesterol when administered as a diet admixture in an acute model of hypercholesterolemia in rats. One analogue (35) also lowered total cholesterol as efficaciously as CL 277,082 in our chronic hypercholesterolemic rat model. The most notable finding of this study is that the SAR of the trisubstituted ureas diverges from that seen in our previously disclosed disubstituted urea series. This series showed optimal activity with 2,4-difluoro and 2,4,6-trifluoro substitution on the urea N-phenyl, whereas the disubstituted series showed optimal activity with bulky 2,6-disubstitution on the phenyl ring.
Collapse
Affiliation(s)
- T S Purchase
- Department of Medicinal Chemistry, Parke-Davis Pharmaceutical Research, Division of Warner-Lambert Company, Ann Arbor, MI 48105, USA
| | | | | | | | | | | | | | | |
Collapse
|
60
|
Uchida T, Usui T, Watanabe T, Higuchi S, Nakata M, Maezawa K, Kikawa Y, Tsunoo M, Nakaya N, Goto Y. Pharmacokinetic properties of YM17E, an inhibitor of acyl coenzyme A: cholesterol acyl transferase, and serum cholesterol levels in healthy volunteers. Eur J Clin Pharmacol 1997; 51:399-406. [PMID: 9049582 DOI: 10.1007/s002280050221] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
We conducted a single and repeat oral dose study of YM17E, a novel inhibitor of acyl coenzyme A (CoA): cholesterol acyltransferase, in healthy male volunteers to evaluate the pharmacokinetic profile, tolerability and effect of the drug on serum cholesterol. In the single administration study, YM17E was administered after a meal to two groups of subjects (each containing six subjects taking the drug and three taking placebo) receiving 3, 60 and 300 mg or 15, 60 and 450 mg YM17E, respectively. Plasma concentrations of unchanged drug following single oral administration at 3-300 mg after a meal increased with increasing dose. In contrast, plasma concentrations after administration of 450 mg were almost the same as after 300 mg. Unchanged YM17E was not detected in urine after single administration, suggesting that it was excreted via the bile or urine after metabolism. Five active metabolites (M1, M2-a, M2-b, M3 and M4) were observed in plasma at concentrations comparable to those of unchanged YM17E. Their plasma concentrations increased in a slightly greater than dose-dependent manner from 3 to 300 mg. The effect of food was studied in an open crossover design with a 1-week washout period. Twelve subjects received 150 mg YM17E in both the fasted and post-prandial states. The AUC and Cmax after fasting were closely similar to those after a meal, showing that bioavailability was not affected by food intake. In the repeated oral dose study, the subjects received test drug at 150 mg or 300 mg (n = 6 each) or placebo (n = 3) twice a day (after breakfast and after dinner) for 7 days. On days 1 and 7, the subjects received YM17E once a day (after breakfast) for evaluation of pharmacokinetic properties. After repeated oral administration of 150 mg b.d., plasma concentrations reached steady state by day 5 (mean Cmin 48.6 ng.ml-1). After repeated administration of 300 mg b.d., plasma concentrations prior to each daily morning dose increased up to the 5th day (mean Cmin 166.6 ng.ml-1) and then tended to decrease until the 7th day. No significant signs, symptoms or changes in serum cholesterol levels were observed during the single and repeated oral dose studies at 150 mg b.d. Although statistical analysis was not conducted because of the small number of subjects, all subjects receiving repeated oral administration of 300 mg twice daily showed a 25% decrease in serum cholesterol level on day 7, but also the simultaneous occurrence of diarrhoea.
Collapse
Affiliation(s)
- T Uchida
- Drug Metabolism Department, Yamanouchi Pharmaceutical Co. Ltd., Tokyo, Japan
| | | | | | | | | | | | | | | | | | | |
Collapse
|
61
|
Abstract
Due to its presumed role in regulating cellular cholesterol homeostasis, and in various pathophysiological conditions, acyl-coenzyme A:cholesterol acyltransferase (ACAT) has attracted much attention. Cloning the ACAT gene provides the necessary tool to advance molecular studies of this enzyme. The topics reviewed in this chapter include the pathophysiological roles of ACAT, the biochemistry and molecular biology of the ACAT protein and the ACAT gene, and the mode of regulation by sterol or nonsterol agents in mammalian cells. In addition, we present a working model linking the presumed allosteric property of ACAT with cholesterol trafficking into and out of the endoplasmic reticulum.
Collapse
Affiliation(s)
- T Y Chang
- Department of Biochemistry, Dartmouth Medical School, Hanover, New Hampshire 03755, USA
| | | | | |
Collapse
|
62
|
Martins IJ, Mortimer BC, Redgrave TG. Effect of the ACAT inhibitor CL 277,082 on apolipoprotein B48 transport in mesenteric lymph and on plasma clearance of chylomicrons and remnants. Arterioscler Thromb Vasc Biol 1997; 17:211-6. [PMID: 9012658 DOI: 10.1161/01.atv.17.1.211] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Inhibitors of acyl CoA:cholesterol acyltransferase (ACAT) activity previously have been found to decrease the absorption of cholesterol and to be effective antiatherosclerotic agents. Effects on chylomicron (CM) transport could contribute to these effects. No previous study has examined the effect of inhibition of ACAT activity on the intestinal lymph output of apolipoprotein (apo) B48 or on the clearance from plasma of lymph CM. In this study, we selected 2,4-difluoro-phenyl-N[[4-(2,2-dimethylpropyl)phenyl]methyl]-N-( hepthyl)urea (CL 277,082) to inhibit intestinal ACAT activity and measured its effects on the output of lipids and apo B48 in intestinal lymph. Compared with control untreated rats, treatment with CL 277,082 decreased the lymph outputs of apo B48 and triglyceride. Associated with the effects on transport, the lymph CM were smaller in diameter in rats treated with CL 277,082. The unesterified cholesterol content of lymph CM was markedly increased and the cholesteryl ester (CE) content was decreased. The contents of triglyceride were decreased and phospholipid was increased. Labeled CM were prepared by feeding donor rats with a test meal containing 3H-cholesterol and 14C-fatty acid. Traced by the CE label in lymph CM in both control rats and rats treated with CL 277,082, the remnants derived after intravenous injection of CM from rats treated with CL 277,082 were cleared significantly more slowly than CM from untreated rats. Moreover, less CE label was recovered in the livers of both groups of rats after injection of CM from rats treated with CL 277,082. Recovery in the spleen was significantly higher in recipient rats injected with CM from rats treated with CL 277,082 when compared with injections of CM obtained from untreated rats. We conclude that the metabolism of CM is affected by treatment with CL 277,082, partly due to the changes in lymph CM composition and partly due to other effects on the recipient rat.
Collapse
Affiliation(s)
- I J Martins
- Department of Physiology, University of Western Australia, Nedlands, Perth, Australia
| | | | | |
Collapse
|
63
|
Kolodgie FD, Katocs AS, Largis EE, Wrenn SM, Cornhill JF, Herderick EE, Lee SJ, Virmani R. Hypercholesterolemia in the rabbit induced by feeding graded amounts of low-level cholesterol. Methodological considerations regarding individual variability in response to dietary cholesterol and development of lesion type. Arterioscler Thromb Vasc Biol 1996; 16:1454-64. [PMID: 8977449 DOI: 10.1161/01.atv.16.12.1454] [Citation(s) in RCA: 102] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
While a number of studies have presented detailed examinations of lesion development in the cholesterol-fed rabbit, individual variability in response to cholesterol feeding and type of lesion produced relative to the degree of cholesterol exposure is not well defined. This study analyzed such critical parameters in an attempt to further characterize the model and establish a baseline for future testing of treatments targeted at limiting atherosclerosis. For these experiments, male New Zealand White rabbits were fed atherogenic diets consisting of 0.05%, 0.10%, 0.15%, 0.20%, or 0.25% cholesterol dissolved in 6% peanut oil for 31 to 32 weeks. Raising dietary cholesterol from 0.05% to 0.15% resulted in a less than twofold stepwise increase in total plasma cholesterol (TPC) exposure (area under plasma cholesterol versus time curve), whereas further increases in cholesterol intake resulted in an exponential four- to fivefold increase in TPC exposure. Regression analysis of TPC exposure with aortic sudanophilia demonstrated a threshold of approximately 5000 cholesterol weeks; below this limit lesions were minimal, and above this value the degree of plaque correlated with TPC exposure. Furthermore, a wide biological variability occurred among rabbits with respect to individual responsiveness to dietary cholesterol. In the aorta, various types of plaques, from fatty streaks to atheromatous lesions, were observed, depending on the degree of cholesterol intake. Diets consisting of < 0.15% cholesterol resulted in the development of fatty streak lesions, while transitional lesions and atheromatous plaques were mostly found with higher cholesterol feeding. Coronary artery atherosclerosis was present in > 50% of animals fed diets > or = 0.15% cholesterol. Despite the level of TPC exposure, coronary lesions in epicardial vessels were generally the fibrous type, whereas intramyocardial arteries demonstrated predominantly intimal foam cells. In conclusion, by adjusting dietary cholesterol intake and selecting rabbits with a similar responsiveness to cholesterol, the overall cholesterol exposure can be more closely controlled to minimize the inherent individual variability among animals in this model. The nature of the target lesion must also be carefully considered, because the efficacy of some treatments may depend on the type of atherosclerotic plaque.
Collapse
Affiliation(s)
- F D Kolodgie
- Department of Cardiovascular Pathology, Armed Forces Institute of Pathology, Washington, DC 20306-6000, USA
| | | | | | | | | | | | | | | |
Collapse
|
64
|
Murakami S, Ohta Y, Asami Y, Yamagishi I, Toda Y, Sato M, Tomisawa K. The hypolipidemic action of the ACAT inhibitor HL-004 in hamsters fed normal chow. GENERAL PHARMACOLOGY 1996; 27:1383-6. [PMID: 9304411 DOI: 10.1016/s0306-3623(96)00070-5] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
1. A novel ACAT (acyl-CoA: cholesterol acyltransferase) inhibitor, HL-004, exhibited a strong inhibitory effect on the hepatic and intestinal ACAT, but was less effective on the adrenal ACAT in vitro. 2. HL-004 selectively decreased serum VLDL cholesterol, and inhibited hepatic ACAT activity in hamsters fed normal chow. 3. These results suggest that the cholesterol-lowering effect of HL-004 can be attributed to a decrease in hepatic VLDL secretion via inhibition of ACAT.
Collapse
Affiliation(s)
- S Murakami
- Medicinal Research Laboratories, Taisho Pharmaceutical Co., Ltd., Saitama, Japan
| | | | | | | | | | | | | |
Collapse
|
65
|
Riddell D, Bright CP, Burton BJ, Bush RC, Harris NV, Hele D, Moore UM, Naik K, Parrott DP, Smith C, Williams RJ. Hypolipidaemic properties of a potent and bioavailable alkylsulphinyl-diphenylimidazole ACAT inhibitor (RP 73163) in animals fed diets low in cholesterol. Biochem Pharmacol 1996; 52:1177-86. [PMID: 8937424 DOI: 10.1016/0006-2952(96)00455-8] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
RP 73163 ((S)-2-[5-(3,5-dimethyl-l-pyrazolyl)pent-l-yl)-sulphinyl]-5, 6-diphenylimidazole) has been shown to be a potent and specific inhibitor of acyl-CoA:cholesterol acyltransferase (EC 2.3.1.26; ACAT) in vitro using the tissues of experimental animals as sources of the enzyme. The concentrations of RP 73163 required to produce 50% inhibition of ACAT activity (IC50 values) in microsomal preparations ranged from 86 nM for rat liver to 370 nM for rabbit intestine. In whole cell assays using human hepatic (HepG2), intestinal (Caco2), and monocytic (THP-1) cell lines, RP 73163 inhibited ACAT activity with IC50 values of 266, 158, and 314 nM, respectively. The addition of RP 73163 (0.03-1.0 microM) to the medium of cultured HepG2 cells produced a concentration-dependent decrease in apolipoprotein B (apoB) secretion. The compound has high systemic bioavailability. Using a bioassay, a concentration of active inhibitor equivalent to 29 microM of parent compound was present in plasma 1 hr after oral administration of RP 73163 (50 mg.kg-1). In rats that had been fed a basal diet ad libitum or starved for 18 hr prior to blood sampling, the administration of RP 73163 (50 mg.kg-1 b.i.d. for 7 days) reduced plasma triglyceride levels by 50% without affecting the concentration of cholesterol. This hypotriglyceridaemic effect was associated with reductions in plasma very-low-density-lipoprotein (VLDL) and low-density-lipoprotein (LDL) levels. RP 73163 decreased the rate of VLDL secretion by 24% in Triton WR-1339-treated rats that had been fasted overnight but did not affect the secretion rate in animals fed ad libitum, indicating that ACAT was only important in regulating VLDL secretion under certain nutritional conditions. RP 73163 reduced the accumulation of intraperitoneally administered [3H]leucine into the plasma VLDL-apoB pool in both fed and fasted states. The results suggest that, in fed animals at least, an increase in the clearance of VLDL from the bloodstream may contribute to the hypolipidaemic activity of the compound. In rabbits with casein-induced endogenous hypercholesterolaemia, RP 73163 specifically reduced the levels of cholesterol carried by LDL. In conclusion, the hypolipidaemic actions of RP 73163, a potent and systemically bioavailable ACAT inhibitor, are consistent with a reduction in the secretion of apoB containing lipoproteins by hepatic tissue and possibly with an increase in the clearance of these particles.
Collapse
Affiliation(s)
- D Riddell
- Rhône-Poulenc Rorer Lt., Dagenham Research Centre, Essex, U.K
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
66
|
Uchida T, Watanabe T, Van Hoogdalem EJ, Higuchi S. In-vitro metabolism of YM17E, an inhibitor of acyl coenzyme A:cholesterol acyltransferase, by liver microsomes in man. J Pharm Pharmacol 1996; 48:1049-56. [PMID: 8953507 DOI: 10.1111/j.2042-7158.1996.tb05898.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Because YM17E (1,3-bis[[1-cycloheptyl-3-(p-dimethylaminophenyl) ureido]methyl]benzene dihydrochloride) inhibits acyl coenzyme A:cholesterol acyltransferase (ACAT) it has potential application in the treatment of hypercholesterolaemia. In man and animals YM17E is extensively metabolized, via N-demethylation, to five active metabolites (M1, M2-a, M2-b, M3 and M4). The main objectives of this study were to examine inhibition of YM17E metabolism by the products and identify the cytochrome P450 isoforms in liver microsomes which catalyse in-vitro YM17E metabolism in man. In microsomes in man N-demethylation of YM17E to M1 occurred enzymatically; for up to 45 s the rate was linearly proportional to the microsomal protein concentration. This reaction was inhibited by metabolites M2-a, M2-b, M3 and M4. Further, N-demethylation of [14C]-YM17E was also inhibited by its product, M1. These results showed that primary metabolism of YM17E was inhibited by its products, and supported the finding that the non-linear increase in plasma concentration of the parent drug and metabolites observed in an in-vivo study was due to inhibition by these products. Metabolic activity in microsomes from ten individual human livers demonstrated that YM17E N-demethylase activity correlated closely with testosterone 6 beta-hydroxylase activity. When cytochrome P450 isozyme-specific substrates and chemical inhibitors were used to inhibit YM17E N-demethylase activity, CYP3A-specific substrate and inhibitors such as nifedipine, ketoconazole and triacetyloleandomycin strongly inhibited this activity, whereas CYP1A-specific substrate or inhibitor, ethoxyresorufin and alpha-naphthoflavone, inhibited weakly. Other CYP inhibitors, in contrast, had few or no effects. An inhibition study using anti-rat CYP1A1, CYP2B1, CYP2C11, CYP2E1 and CYP3A2 antibodies demonstrated that only anti-rat CYP3A2 antibody inhibited YM17E metabolism, to 40% of control level, with no other antibodies showing an inhibitory effect. Of seven cDNA-expressed P450 isoforms in man (CYP1A1, CYP1A2, CYP2A6, CYP2B6, CYP2D6, CYP2E1 and CYP3A4), CYP3A4, CYP2D6 and CYP1A2 isozyme exhibited substantial catalytic activity of N-demethylation of YM17E. These results indicate the predominant role of CYP3A4 in liver metabolism of YM17E in man.
Collapse
Affiliation(s)
- T Uchida
- Drug Metabolism Department, Yamanouchi Pharmaceutical Co. Ltd, Tokyo, Japan
| | | | | | | |
Collapse
|
67
|
Clader JW, Burnett DA, Caplen MA, Domalski MS, Dugar S, Vaccaro W, Sher R, Browne ME, Zhao H, Burrier RE, Salisbury B, Davis HR. 2-Azetidinone cholesterol absorption inhibitors: structure-activity relationships on the heterocyclic nucleus. J Med Chem 1996; 39:3684-93. [PMID: 8809157 DOI: 10.1021/jm960405n] [Citation(s) in RCA: 101] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
A series of azetidinone cholesterol absorption inhibitors related to SCH 48461 ((-)-6) has been prepared, and compounds were evaluated for their ability to inhibit hepatic cholesteryl ester formation in a cholesterol-fed hamster model. Although originally designed as acyl CoA: cholesterol acyltransferase (ACAT) inhibitors, comparison of in vivo potency with in vitro activity in a microsomal ACAT assay indicates no correlation between activity in these two models. The molecular mechanism by which these compounds inhibit cholesterol absorption is unknown. Despite this limitation, examination of the in vivo activity of a range of compounds has revealed clear structure-activity relationships consistent with a well-defined molecular target. The details of these structure-activity relationships and their implications on the nature of the putative pharmacophore are discussed.
Collapse
Affiliation(s)
- J W Clader
- Schering-Plough Research Institute, Kenilworth, New Jersey 07033-0539, USA
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
68
|
Kogushi M, Tanaka H, Ohtsuka I, Yamada T, Kobayashi H, Saeki T, Takada M, Hiyoshi H, Yanagimachi M, Kimura T, Yoshitake S, Saito I. Anti-atherosclerotic effect of E5324, an inhibitor of acyl-CoA:cholesterol acyltransferase, in Watanabe heritable hyperlipidemic rabbits. Atherosclerosis 1996; 124:203-10. [PMID: 8830933 DOI: 10.1016/0021-9150(96)05831-5] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
E5324, n-butyl-N'-[2-[3-(5-ethyl-4-phenyl-1H-imidazol-1-yl)propoxy]-6- methylphenyl]urea, a novel and potent inhibitor of acyl-CoA:cholesterol acyltransferase (ACAT), was evaluated for its anti-atherosclerotic and lipid-lowering effects in Watanabe heritable hyperlipidemic (WHHL) rabbits. At 3 months of age, 40 male WHHL rabbits were divided into 4 groups. The rabbits were fed a standard rabbit chow (control group), or standard rabbit chow containing E5324 (0.1% or 0.02%) or 1% probucol for 16 weeks. Even the high dose of E5324 did not lower the plasma total cholesterol levels throughout the experiment. Probucol slightly reduced the plasma cholesterol levels, and showed anti-atherosclerotic activity, i.e., reductions of atherosclerotic plaque formation and cholesterol content in the aorta. Although E5324 did not lower plasma cholesterol, atherosclerotic plaque formation in the aortic arch and thoracic aorta was reduced (by about 34% and 41%, respectively, at the high dose; P < 0.05). Cholesterol content in the aortic arch and thoracic aorta was also reduced (by about 59% and 62% at the high dose, respectively) compared with the control. These results suggest that E5324 acts directly on the arterial wall through ACAT inhibition, and prevents the progression of atherosclerosis in WHHL rabbits.
Collapse
Affiliation(s)
- M Kogushi
- Eisai Tsukuba Research Laboratories, Eisai Co. Ltd., Ibaraki, Japan
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
69
|
Novel 4,4-bis(trifluoromethyl) imidazolines as stereospecific and orally active acyl coa: Cholesterol acyltransferase (ACAT) inhibitors and antihypercholesterolemic agents. Bioorg Med Chem Lett 1996. [DOI: 10.1016/0960-894x(96)00137-0] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
|
70
|
Astles PC, Ashton MJ, Bridge AW, Harris NV, Hart TW, Parrott DP, Porter B, Riddell D, Smith C, Williams RJ. Acyl-CoA:Cholesterol O-acyltransferase (ACAT) inhibitors. 2. 2-(1,3-Dioxan-2-yl)-4,5-diphenyl-1H-imidazoles as potent inhibitors of ACAT. J Med Chem 1996; 39:1423-32. [PMID: 8691472 DOI: 10.1021/jm9505876] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
The second in this series of papers concerns our further investigations into the search for a potent bioavailable acyl-CoA:cholesterol O-acyltransferase (ACAT) inhibitor suitable for the treatment of atherosclerosis. The design, synthesis, and structure-activity relationship for a series of ACAT inhibitors based on the 2-(1,3-dioxan-2-yl)-4,5-diphenyl-1H-imidazole pharmacophore are described. Compounds such as 13a bearing simple alkyl or hydroxymethyl substituents at the 5-position of the 1,3-dioxane ring are potent bioavailable inhibitors of the rat hepatic microsomal enzyme in vitro (IC50 < 100 nM) but are only weak inhibitors of the human hepatic enzyme. We have found however that 1,3-dioxanes substituted at the 5-cis position with pyrazolylalkyl or aminoalkyl groups are potent inhibitors in vitro of human macrophage ACAT, the potency depending on the nature of the terminal heterocycle and the length of the alkyl chain. An ex vivo bioassay herein demonstrates that potent inhibitors such as 13t (IC50 = 10 nM) which contain lipophilic terminal heterocycles do not appear to be systematically available. Less potent but more water soluble compounds such as 13h (IC50 = 60 nM) and 13n (IC50 = 70 nM) are absorbed following oral dosing and achieve plasma levels significantly in excess of their IC50 for ACAT inhibition. These compounds are therefore possible candidates for further investigation as oral antiatherosclerotic agents.
Collapse
Affiliation(s)
- P C Astles
- Rhône-Poulenc Rorer, Dagenham Research Centre, Dagenham, Essex, U.K
| | | | | | | | | | | | | | | | | | | |
Collapse
|
71
|
Lopez-Candales A, Grosjlos J, Sasser T, Buddhiraju C, Scherrer D, Lange LG, Kumar VB. Dietary induction of pancreatic cholesterol esterase: a regulatory cycle for the intestinal absorption of cholesterol. Biochem Cell Biol 1996; 74:257-64. [PMID: 9213435 DOI: 10.1139/o96-027] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Atherosclerosis has a strong dietary basis without a proven molecular mechanism for cholesterol absorption. To investigate the potential role of pancreas in this process and its interaction with the two dietary forms of cholesterol (free and esterified), we undertook to study the role of pancreatic cholesterol esterase in cholesterol absorption. The results showed that (i) cholesterol esters contribute a disproportionately high fraction of absorbed dietary cholesterol, (ii) rates of intestinal cholesterol absorption are related to pancreatic cholesterol esterase activity, (iii) mRNA specific for pancreatic cholesterol esterase is induced 15-fold by dietary sterol esters and 10-fold by free sterol, (iv) the induction of cholesterol esterase mRNA is reversible, and (v) free cholesterol transport into cultured human intestinal cells is enhanced 300% by pancreatic cholesterol esterase. These data implicate pancreatic cholesterol esterase as pivotal in a metabolic loop under positive feedback control for the absorption of dietary cholesterol, whether free or esterified.
Collapse
|
72
|
|
73
|
Kusunoki J, Aragane K, Kitamine T, Higashinakagawa S, Kase N, Yamaura T, Ohnishi H. Hypocholesterolemic action and prevention of cholesterol absorption via the gut by F-1394, a potent acyl-CoA:cholesterol acyltransferase (ACAT) inhibitor, in cholesterol diet-fed rats. JAPANESE JOURNAL OF PHARMACOLOGY 1995; 69:53-60. [PMID: 8847832 DOI: 10.1254/jjp.69.53] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
In the present study, we investigated the hypocholesterolemic effect of F-1394 ((1s,2s)-2-[3-(2,2-dimethylpropyl)-3-nonylureido]aminocycloh exane-1-yl 3-[N-(2,2,5,5-tetramethyl-1,3-dioxane-4-carbonyl)amino] propionate), a potent and selective inhibitor of acyl-CoA:cholesterol acyltransferase (ACAT), and the effect on cholesterol absorption via the gut in rats fed a 1% cholesterol diet. Single administration of F-1394 to the cholesterol diet-fed rats at the doses of 3-30 mg/kg, p.o. decreased the serum cholesterol levels by 16-54% 3 hr after the administration. The ACAT activity in the small intestinal mucosa of the rats given orally F-1394 (30 mg/kg) was significantly inhibited 3 hr after the administration. The hypocholesterolemic action of F-1394 had a faster onset than that of DL-melinamide or CL-277,083. The study by the dual isotope ratio method showed that F-1394 (30 mg/kg, p.o.) significantly suppressed the dietary cholesterol absorption. Furthermore, in the determination of cholesterol absorption by using 14C-cholesterol as the oral tracer, the administration of F-1394 (30 mg/kg, p.o.) 1 or 2 hr before or immediately after the application of the oral tracer significantly prevented the appearance of the radioactivity in the circulation by around 90%. These results indicate that oral administration of F-1394 inhibits the ACAT activity in the small intestinal mucosa and subsequently contributes much to the prevention of cholesterol absorption via the gut, resulting in the decrease in serum cholesterol levels in the cholesterol diet-fed rats. Furthermore, the effect of F-1394 appears immediately after its administration in contrast to that of DL-melinamide or CL-277,082.
Collapse
Affiliation(s)
- J Kusunoki
- Pharmaceuticals Research Laboratories, Fujirebio, Inc., Tokyo, Japan
| | | | | | | | | | | | | |
Collapse
|
74
|
Synthesis and pharmacological profile of FCE 28654: A water-soluble and injectable ACAT inhibitor. Bioorg Med Chem Lett 1995. [DOI: 10.1016/0960-894x(95)00275-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
|
75
|
ACAT inhibitors CL 283,546 and CL 283,796 reduce LDL cholesterol without affecting cholesterol absorption in African green monkeys. J Lipid Res 1995. [DOI: 10.1016/s0022-2275(20)41128-9] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
|
76
|
Ishigami K, Kitahara T. Synthesis of all the four possible stereoisomers of acaterin, naturally occurring ACAT inhibitor, and the determination of its absolute configuration. Tetrahedron 1995. [DOI: 10.1016/0040-4020(95)00303-p] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
|
77
|
Kogushi M, Tanaka H, Kobayashi H, Yamada T, Ohtsuka I, Kimura T, Saito I. Effect of E5324, a novel inhibitor of acyl-CoA:cholesterol acyltransferase, on cholesteryl ester synthesis and accumulation in macrophages. JAPANESE JOURNAL OF PHARMACOLOGY 1995; 68:191-9. [PMID: 7563976 DOI: 10.1254/jjp.68.191] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The in vitro potencies of a novel inhibitor of acyl-CoA:cholesterol acyltransferase (ACAT), E5324 (n-butyl-N'-[2-[3-(5-ethyl-4-phenyl-1H-imidazol-1-yl)propoxy]-6- methylphenyl]urea), were studied. E5324 was found to be a potent ACAT inhibitor in microsomes from a various tissues and in cultured cell homogenate, with IC50 values in the range of 0.044 to 0.19 microM. The kinetic study on E5324 showed that the inhibition of rat intestine ACAT was competitive with respect to oleoyl CoA. E5324 inhibited [3H]olate incorporation into cholesteryl [3H]oleate in phorbol ester-treated THP-1 cell lines (IC50 = 0.44 microM). The rate of [3H]oleate incorporation into phospholipids and triglycerides was not affected by E5324. In an experiment with [3H]cholesterol as the substrate for ACAT, E5324 also inhibited [3H]cholesteryl ester synthesis (IC50 = 0.41 microM). Furthermore, E5324 prevented accumulation of both esterified and total cholesterol in acetyl low density lipoprotein-loaded THP-1 cells. These results indicate that E5324 is a potent and selective ACAT inhibitor and prevents cholesteryl ester accumulation in macrophages.
Collapse
Affiliation(s)
- M Kogushi
- Eisai Tsukuba Research Laboratories, Eisai Co., Ltd., Ibaraki, Japan
| | | | | | | | | | | | | |
Collapse
|
78
|
Salisbury BG, Davis HR, Burrier RE, Burnett DA, Bowkow G, Caplen MA, Clemmons AL, Compton DS, Hoos LM, McGregor DG. Hypocholesterolemic activity of a novel inhibitor of cholesterol absorption, SCH 48461. Atherosclerosis 1995; 115:45-63. [PMID: 7669087 DOI: 10.1016/0021-9150(94)05499-9] [Citation(s) in RCA: 90] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The amount of cholesterol that circulates in the plasma as lipoproteins can be affected by the balance of cholesterol metabolism within and between the intestines and liver. In the present report, we describe a novel hypocholesterolemic agent and document its pharmacological effects in animal models of hypercholesterolemia. The oral administration of (3R,4S)-1,4-bis-(4-methoxyphenyl)-3-(3-phenylpropyl)-2-azetidinone (SCH 48461) reduced plasma cholesterol concentrations in cholesterol-fed hamsters, rats and rhesus monkeys with ED50s of 1, 2 and 0.2 mg/kg per day, respectively, SCH 48461 was also highly effective in reducing hepatic cholesteryl ester accumulation in cholesterol-fed hamsters and rats after 7 days of treatment. In one 3 week study, rhesus monkeys were fed a 0.25% cholesterol/22% saturated fat diet with or without SCH 48461. At the end of the 3 week period the control group's VLDL + LDL-cholesterol increased to 180 Mg/dl from a baseline of approximately 65 mg/dl while plasma apolipoprotein B levels had doubled. Animals treated daily with 1 mg/kg SCH 48461 maintained their baseline levels of VLDL + LDL-cholesterol, HDL-cholesterol, and plasma apolipoproteins B and A-I. After 3 weeks the diets of the two groups were switched. Within 1 week SCH 48461 (1 mg/kg per day) rapidly reversed the elevated VLDL + LDL-cholesterol levels of the previous control group to near baseline values. SCH 48461 exerted its hypocholesterolemic effect through the inhibition of cholesterol absorption. A dose of 10 mg/kg per day inhibited cholesterol absorption in cholesterol-fed hamsters by 68% while a similar reduction was achieved in chow-fed monkeys with 3 mg/kg per day. This latter dose inhibited cholesterol absorption in cholesterol-fed monkeys by 95%. Treatment of cholesterol-fed monkeys with 10 mg/kg per day SCH 48461 significantly increased fecal neutral sterol excretion (52 vs. 32 mg/kg) but had no effect on acidic sterol excretion. Using a 2-h absorption model in cholesterol-fed hamsters, SCH 48461 caused a 46% inhibition of unesterified [14C]cholesterol accumulation in the intestinal wall and a 90% inhibition of cholesteryl ester formation at a dose of 10 mg/kg. Similar data were observed when the plasma radioactivity was assessed, indicating inhibition of both free (61%) and esterified (85%) cholesterol appearance. In contrast, CI-976, a potent acyl-CoA:cholesterol acyltransferase (ACAT) inhibitor, did not affect the uptake of free cholesterol into the intestines while inhibiting cholesterol esterification (98% inhibition).(ABSTRACT TRUNCATED AT 400 WORDS)
Collapse
Affiliation(s)
- B G Salisbury
- Schering-Plough Research Institute, Kenilworth, NJ 07033-0539, USA
| | | | | | | | | | | | | | | | | | | |
Collapse
|
79
|
Kusunoki J, Aragane K, Yamaura T, Ohnishi H. Studies on acyl-CoA: cholesterol acyltransferase (ACAT) inhibitory effects and enzyme selectivity of F-1394, a pantotheic acid derivative. JAPANESE JOURNAL OF PHARMACOLOGY 1995; 67:195-203. [PMID: 7630037 DOI: 10.1254/jjp.67.195] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
(1s,2s)-2-[3-(2,2-Dimethylpropyl)-3-nonylureido]aminocyclohe xane-1-yl 3-[N-(2,2,5,5-tetramethyl-1,3-dioxane-4-carbonyl)amino]propionate (F-1394), a pantotheic acid derivative, is a newly synthesized inhibitor of acyl-CoA:cholesterol acyltransferase (ACAT). In the present study, we investigated the inhibitory effects of F-1394 on the activities of ACAT. F-1394 reduced the ACAT activities in rat liver microsomes, homogenate of rabbit small intestinal mucosa and lysate of J774 macrophages with IC50 values of 6.4 nM, 10.7 nM and 32 nM, respectively. The kinetic studies showed that F-1394 exerted competitive-type inhibition, and the Ki values in liver and small intestinal ACAT were 4.0 nM and 9.9 nM, respectively. The inhibitory effects of F-1394 on the activity of ACAT were more potent than that of other ACAT inhibitors or hypolipidemic agents. The study on enzyme selectivity indicated that F-1394 did not affect 3-hydroxy-3-methylglutaryl CoA reductase, acyl-CoA synthetase and cholesterol esterase. F-1394 weakly inhibited the activity of lecithine:cholesterol acyltransferase (LCAT) originating from rat plasma. The inhibitory potency of F-1394 for the activity of liver microsomal ACAT was 4,690-fold stronger than that for the activity of LCAT. These findings indicate that F-1394 is a potent and selective inhibitor of ACAT, and its inhibition manner is the competitive type.
Collapse
Affiliation(s)
- J Kusunoki
- Pharmaceuticals Research Laboratories, Fujirebio Inc., Tokyo, Japan
| | | | | | | |
Collapse
|
80
|
Nagata Y, Yonemoto M, Iwasawa Y, Shimizu-Nagumo A, Hattori H, Sawazaki Y, Kamei T. N-[2-[N'-pentyl-(6,6-dimethyl-2,4-heptadiynyl)amino]ethyl]- (2-methyl-1-naphthylthio)acetamide (FY-087). A new acyl coenzyme a:cholesterol acyltransferase (ACAT) inhibitor of diet-induced atherosclerosis formation in mice. Biochem Pharmacol 1995; 49:643-51. [PMID: 7887979 DOI: 10.1016/0006-2952(94)00510-s] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
FY-087 (N-[2-[N'-pentyl-(6,6-dimethyl-2,4-heptadiynyl)amino]ethyl]- (2-methyl-1-naphthylthio)acetamide) was found to be a competitive inhibitor of human microsomal acyl coenzyme A:cholesterol acyltransferase (ACAT) with an IC50 value of 0.11 microM. Under our assay conditions, other ACAT inhibitors tested, specifically YM-750, E-5324, and melinamide, all of which are now in phase I clinical trials or in clinical use in Japan, inhibited this enzyme with IC50 values of 0.18, 0.14, and 3.2 microM, respectively. FY-087 also inhibited ACAT in acetyl-low density lipoprotein loaded human macrophages (THP-1 cells) with an IC50 of 0.17 microM. Following the oral administration of FY-087 (30 mg/kg) to rats, the plasma concentration of FY-087 reached 0.42 microgram/mL after 2 hr. This concentration of FY-087 was enough to inhibit blood vessel ACAT activity. Cholesterol-lowering and anti-atherogenic effects of FY-087 were examined using C57BL/6J mice fed an atherogenic diet. In this mouse model, treatment with FY-087 (28 mg/kg) inhibited the increase in plasma cholesterol levels by about 20% and decreased the hepatic accumulation of free and esterified cholesterol by 61 and 67%, respectively. FY-087 also significantly inhibited the atherogenic diet-induced increase in the fatty-streak lesion area of the proximal aorta by 57% in C57BL/6J mice. These results indicate that FY-087 is not only a therapeutically bioavailable ACAT inhibitor that lowers plasma cholesterol levels, but also an effective anti-atherogenic agent in mice fed an atherogenic diet.
Collapse
Affiliation(s)
- Y Nagata
- Tsukuba Research Institute, Banyu Pharmaceutical Co., Ltd., Tsukuba, Japan
| | | | | | | | | | | | | |
Collapse
|
81
|
Murakami S, Araki H, Otomo S, Nara Y, Yamori Y. Effects of HL-004, a novel ACAT inhibitor, on cholesterol accumulation and removal in cultured smooth muscle cells from stroke-prone spontaneously hypertensive rats (SHRSP). Life Sci 1995; 56:509-20. [PMID: 7869831 DOI: 10.1016/0024-3205(94)00480-g] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
The cholesterol metabolism of cultured smooth muscle cells (SMC) from the thoracic aorta of SMC from stroke-prone spontaneously hypertensive rats (SHRSP) and Wistar-Kyoto rats (WKY) was compared. SMC from SHRSP had a higher acylCoA:cholesterol acyltransferase (ACAT) activity and accumulated more cholesterol than those from WKY. By using SMC from SHRSP, the effects of a novel ACAT inhibitor, HL-004, on the accumulation and removal of cholesterol were investigated. HL-004 inhibited microsomal ACAT activity from rabbit liver, intestine, aorta, and cultured SMC of SHRSP with 50% inhibition (IC50) values of 2.2, 1.7, 7.9, and 20 nM, respectively. HL-004 suppressed the accumulation of the intracellular cholesteryl ester (CE), but did not affect the intracellular free cholesterol (FC) content. Removal of cholesterol from the lipid-loaded SMC was accelerated by HL-004. These effects of HL-004 on cholesterol levels showed a good parallel to ACAT inhibition. It would thus appear that the suppression of cholesterol accumulation and the removal of cholesterol in SMC by HL-004 can be attributed to its ACAT inhibition in the cell, which reduces the content of intracellular CE.
Collapse
Affiliation(s)
- S Murakami
- Research Center, Taisho Pharmaceutical Co. Ltd., Ohmiya, Japan
| | | | | | | | | |
Collapse
|
82
|
Abstract
The effectiveness of plasma lipid lowering in the clinic is well supported by a growing number of contributions, indicating the significant improvement in cardiovascular risk in primary and particularly in secondary prevention. While these studies have clearly indicated that the more potent agents for cholesterol reduction can provide a very effective help, other pathways of lipid metabolism have gained interest. These should be evaluated, in the hope of providing a more complete answer to the question of regulating lipid absorption, distribution, and tissue deposition. In addition to newer more potent systemic lipid-lowering drugs (in particular hydroxymethylglutaryl coenzyme A reductase inhibitors), nonsystemic agents, including cholesterol sequestrants, are receiving attention. Some of these are effective at low concentrations, thus providing a potentially powerful tool for plasma cholesterol regulation. Another area of development is that of acyl coenzyme A cholesterol acyltransferase inhibitors, i.e., drugs interfering with cholesterol esterification in tissues, particularly in the arterial wall; the major problem with these seems to be that of poor tolerability and of lack of definitive proof of plasma cholesterol reduction in humans. At present, drugs for the treatment of elevated lipoprotein(a) levels are not available, with few exceptions; in this case, a better understanding of the regulation of lipoprotein(a) metabolism and of the potential benefit of treatment seems necessary. Elevation of congenitally low high density lipoprotein cholesterol levels may also be an important target: microsomal enzyme inducers have been tested, but have not provided a clinically significant response; drugs with a mixed endocrine-hypolipidemic activity possibly may prove effective. Other targets, e.g., the correction of the lipoprotein pattern characterized by "small low density lipoprotein," and the development of drugs specifically acting on the cholesteryl ester transfer protein and lipoprotein lipase systems, are being explored. Finally, new areas of development are in recombinant apolipoproteins (apo's) and in gene therapy. One case, i.e., that of apo A-I/HDL, is entering the clinical field; the mutant apo A-IMilano might provide help because of a combined cholesterol removing/fibrinolytic activity. In the case of gene therapy, at present, data on low density lipoprotein receptor replacement are encouraging. Further options, such as gene transfer in the arterial wall to induce vascular protection/disobliteration of occlusions, are also being tested.
Collapse
Affiliation(s)
- C R Sirtori
- Center E. Grossi Paoletti, University of Milano, Italy
| |
Collapse
|
83
|
Uchida T, Nakamura E, Usui T, Imasaki H, Kawakami R, Watanabe T, Higuchi S. Disposition and metabolism of a novel diurea inhibitor of acyl CoA: cholesterol acyltransferase (YM17E) in the rat and dog. Xenobiotica 1994; 24:1223-36. [PMID: 7771109 DOI: 10.3109/00498259409038678] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
1. We have investigated the disposition and metabolism of YM17E after intravenous and oral administration in the rat and dog. 2. Bioavailability of YM17E was 5-9% at oral doses of 3-30 mg/kg in rat, and 9 and 13% at oral doses of 10 and 30 mg/kg in dog. 3. Five N-demethylated metabolites, which have significant pharmacological activity, were found in rat and dog plasma after oral administration. Plasma concentrations of each of these metabolites were comparable with that of unchanged drug. 4. When 14C-YM17E was administered to rat, AUC of unchanged drug was 7% of that of radioactivity. However, AUC of the combined concentration of unchanged drug and five active metabolites was about 50% of that of radioactivity, indicating that the pharmacological activity of the agent was maintained in spite of its biotransformation. 5. After oral administration of 14C-YM17E at a dose of 10 mg/kg to rat, radioactivity was distributed widely to almost all tissues except the brain. The concentration of radioactivity in the liver, one of the target organs, was 65 times higher than that in plasma at 1 h after administration. 6. A significant amount of radioactivity in the liver was located in the microsomal subfraction, which contains much acyl CoA:cholesterol acyl transferase activity. More than 50% of this microsomal radioactivity was derived from unchanged YM17E and five active metabolites. 7. From excretion data in the bile duct-cannulated rat, the absorption ratio of YM17E from the gastrointestinal tract in this species was estimated to be at least 40%, suggesting that the low bioavailability of the drug is due to extensive first-pass metabolism. 8. Some 95% of the administered radioactivity was excreted in the faeces of rat following iv or po doses of 14C-YM17E.
Collapse
Affiliation(s)
- T Uchida
- Drug Metabolism Department, Yamanouchi Pharmaceutical Co. Ltd, Tokyo, Japan
| | | | | | | | | | | | | |
Collapse
|
84
|
Pharmacological properties of a novel ACAT inhibitor (CP-113,818) in cholesterol-fed rats, hamsters, rabbits, and monkeys. J Lipid Res 1994. [DOI: 10.1016/s0022-2275(20)39778-9] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
|
85
|
White DA, Heffron F, Knight D, Salter AM. The effects of two acylcoenzyme A: cholesterol acyltransferase (ACAT) inhibitors, cyclandelate and a non-hydrolysable ether analogue, benzyl3,3,5-trimethylcyclohexanol on low density lipoprotein metabolism in macrophages and hepatocytes. Biochem Pharmacol 1994; 48:915-22. [PMID: 8093104 DOI: 10.1016/0006-2952(94)90362-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Cyclandelate (3,3,5-trimethylcyclohexanylmandelate) caused a dose-dependent decrease in the metabolism of radioiodinated low density lipoprotein [125I-LDL] by J774 mouse macrophages. This was probably an indirect effect due to the inhibition of cholesterol esterification by the cells rather than a direct one on the interaction of LDL with its receptor, since no inhibition was seen in cells which had been cholesterol-depleted by prior incubation with lipoprotein-depleted serum for 48 hr. Cyclandelate also inhibited immediately de novo synthesis of cholesterol from [1-14C]acetate in J774 cells, suggesting a direct action of the drug on an enzyme of the cholesterol biosynthetic pathway. The drug was an efficient inhibitor of hamster and rat intestinal acylcoenzyme A: cholesterol acyltransferase (ACAT) activity in vitro with an IC50 of 20 microM. Addition of cyclandelate to the diet of meal-fed rats caused a marked inhibition of the rate of appearance of dietary [4-14C]cholesterol in the plasma. A nonhydrolysable ether analogue of cyclandelate, benzyl3,3,5-trimethylcyclohexanol, was prepared to compare hepatic and extrahepatic actions of the two molecules. The analogue inhibited cholesterol esterification in J774 cells, transformed human macrophages U937 and human umbilical vein endothelial cells with an IC50 of 20 microM and had effects similar to those of cyclandelate on 125I-LDL metabolism in J774 cells. Differences between the analogue and cyclandelate were seen in hepatocytes and hepatic microsomal fractions, where preincubation with the analogue inhibited cholesterol esterification in both systems while cyclandelate had no inhibitory action in either. Consequently, preincubation of rat hepatocytes with benzyl3,3,5-trimethylcyclohexanol for 17 hr caused a marked decrease in the binding of 125I-LDL to the cells, whereas binding to cells preincubated with cyclandelate was the same as to control cells.
Collapse
Affiliation(s)
- D A White
- Department of Biochemistry, University of Nottingham Medical School, U.K
| | | | | | | |
Collapse
|
86
|
Tanaka H, Ohtsuka I, Kogushi M, Kimura T, Fujimori T, Saeki T, Hayashi K, Kobayashi H, Yamada T, Hiyoshi H. Effect of the acyl-CoA:cholesterol acyltransferase inhibitor, E5324, on experimental atherosclerosis in rabbits. Atherosclerosis 1994; 107:187-201. [PMID: 7980693 DOI: 10.1016/0021-9150(94)90020-5] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
E5324, n-butyl-N'-[2-[3-(5-ethyl-4-phenyl-1H-imidazol-1-yl)propoxy]-6- methylphenyl]urea, a novel and orally absorbable acyl-CoA:cholesterol acyltransferase (ACAT) inhibitor, was evaluated for its antiatherosclerotic and antihyperlipidemic effects in cholesterol-fed hypercholesterolemic rabbits. When administered concurrently with a high-cholesterol (0.5% cholesterol) diet for 12 weeks, E5324 (0.0025%, 0.005% and 0.01% in diet) lowered plasma total cholesterol levels dose-dependently (by about 55%-87% at the end of the experiment compared with the control) and also reduced atherosclerotic plaque formation (about 90% reduction at the highest dose; P < 0.01). In pre-established hypercholesterolemic rabbits, which had been pre-fed a high-cholesterol diet for 8 weeks, E5324 administered in the same diet at a dose of 0.005%, 0.01% or 0.02% for 4 weeks significantly reduced plasma cholesterol levels dose-dependently. Cholesterol content and ACAT activity in the aortic arch were also decreased (by about 72% and 58% at the highest dose, respectively) compared with the control. Another ACAT inhibitor, CI-976, had a similar action, but cholestyramine and probucol (2% and 1% in diet, respectively) lacked anti-atherosclerotic activity in this model. Furthermore, when pre-established hypercholesterolemic rabbits were fed normal rabbit chow diet with or without 0.02% E5324 for 4 weeks, changes in plasma cholesterol levels were similar in both E5324-treated and control groups. On the other hand, E5324 significantly reduced cholesterol content and ACAT activity in the aortic arch (by about 52% and 50%, respectively) compared with the control group. These results indicate that E5324 not only has hypocholesterolemic activity, but also may have a direct effect on the arterial wall in experimental atherosclerosis.
Collapse
Affiliation(s)
- H Tanaka
- Eisai Tsukuba Research Laboratories, Eisai Company Ltd., Ibaraki, Japan
| | | | | | | | | | | | | | | | | | | |
Collapse
|
87
|
Abstract
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.
Collapse
Affiliation(s)
- K Matsuda
- Cardiovascular & Atherosclerosis Research Laboratories, Yamanouchi Institute for Drug Discovery Research, Yamanouchi Pharmaceutical Co. Ltd., Ibaraki Pref., Japan
| |
Collapse
|
88
|
Augelli-Szafran CE, Roth BD, Essenburg A, Hamelehle KL, Krause BR, Stanfield RL. Imidazolidinones and pyrazolones as novel ACAT inhibitors: Chemistry and biological activity. Bioorg Med Chem Lett 1994. [DOI: 10.1016/s0960-894x(01)80235-3] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
|
89
|
Burrier RE, Deren S, McGregor DG, Hoos LM, Smith AA, Davis HR. Demonstration of a direct effect on hepatic acyl CoA: cholesterol acyl transferase (ACAT) activity by an orally administered enzyme inhibitor in the hamster. Biochem Pharmacol 1994; 47:1545-51. [PMID: 8185666 DOI: 10.1016/0006-2952(94)90530-4] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Orally active inhibitors of acyl CoA:cholesterol acyl transferase (ACAT), such as Lederle CL277082 (LE), are known to reduce plasma and hepatic cholesteryl ester levels, although the mechanisms are not well understood. Several groups have reported the inhibition of cholesterol absorption upon oral ACAT inhibitor administration. In this study, we used 7-day dietary and drug treatments of hamsters to examine the possible effects of LE on hepatic ACAT. ACAT assays were performed using liver homogenates in the absence and presence of a saturating level of exogenously added cholesterol. LE (100 mg/kg/day) treatment of chow or 0.5% cholesterol-fed animals caused reductions in ACAT activity without additional cholesterol as compared with non-treated animals. When a saturating level of cholesterol was added to the assays, reductions in ACAT activity upon LE treatment of chow- or cholesterol-fed animals were also observed. Treatment of cholesterol-fed animals with cholestyramine in the diet reduced ACAT activity in the absence of added cholesterol. However, ACAT activities similar to those of non-treated animals were observed at a saturating level of cholesterol. This latter effect demonstrates that inhibition of cholesterol absorption reduces cholesterol delivery to the liver but does not reduce cholesterol esterifying capacity since cholestyramine is not absorbed and has no direct effect on the liver. The decreased ACAT activity in homogenates from LE-treated animals could also be mimicked in a dose-dependent manner by the addition of exogenous LE to liver homogenates from non-treated animals. These results indicate that hepatic ACAT activity is regulated by the availability of free cholesterol, and that orally administered LE has a direct effect on hepatic ACAT activity in the liver. In addition, the data are consistent with LE activity in the liver as being responsible, in part, for the reduced hepatic and plasma cholesteryl esters in treated animals.
Collapse
Affiliation(s)
- R E Burrier
- Schering-Plough Research Institute, Kenilworth, NJ 07033-0539
| | | | | | | | | | | |
Collapse
|
90
|
Fancelli D, Chiari A, Cozzi P, Lovisolo P, Severino D, Ghiselli G. Imidazolylbenzopyrane derivatives: a new class of acyl-CoA: cholesterol acyltransferase (ACAT) inhibitors. JOURNAL OF ENZYME INHIBITION 1994; 8:159-72. [PMID: 7539485 DOI: 10.3109/14756369409020198] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Inhibitors of the enzyme Acyl-CoA: Cholesterol Acyltransferase are regarded as potentially useful agents in the treatment of hypercholesterolemia and atherosclerosis. We report here a novel series of 2, 6-disubstituted-3-imidazolylbenzopyrane derivatives with significant in vitro ACAT inhibitory activity (IC50 range 0.05-0.5 microM). Compounds of this series such as 26 are examples of a new, structurally distinct class of potent ACAT inhibitors with high specificity for the aortic subtype of the enzyme. The structure-activity relationships of the 3-imidazolylbenzopyrane ACAT inhibitors were investigated by systematic manipulation of two regions of the parent compound 1 and the inhibitory activity resulted linked to the substituent in position 6 of the benzopyrane ring and modulated by the size of lipophilic substituents in position 2. Investigation of the mechanism of the inhibitory effect leads to the conclusion that these compounds act in a non-competitive fashion.
Collapse
Affiliation(s)
- D Fancelli
- Pharmacia Farmitalia Carlo Erba Research Institute, Milan, Italy
| | | | | | | | | | | |
Collapse
|
91
|
Roach PD, Balasubramaniam S, Hirata F, Abbey M, Szanto A, Simons LA, Nestel PJ. The low-density lipoprotein receptor and cholesterol synthesis are affected differently by dietary cholesterol in the rat. BIOCHIMICA ET BIOPHYSICA ACTA 1993; 1170:165-72. [PMID: 8399341 DOI: 10.1016/0005-2760(93)90067-j] [Citation(s) in RCA: 49] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
In the hamster and the rabbit, the low-density lipoprotein (LDL) receptor and cholesterol synthesis are coordinately downregulated by dietary cholesterol. In the rat, cholesterol synthesis is downregulated but LDL kinetic studies suggest that the LDL receptor is not. The aim of this study was to determine the effect of dietary cholesterol on the expression of the hepatic LDL receptor in the rat. Young (2 months) hooded and albino Wistar rats and older (9 months) Sprague-Dawley rats were used because of their reported different propensities to develop hypercholesterolaemia when fed cholesterol. Hepatic LDL receptor activity was measured using a dot blot assay with LDL-gold and LDL receptor mass was measured using an electroblot assay with a polyclonal antibody. Dietary cholesterol had no effect on the plasma cholesterol concentration in both strains of young Wistar rats but increased it in the older Sprague-Dawley rats. Cholesterol synthesis as measured with 3H2O or as indicated by 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase activity or the ratio of plasma lathosterol to cholesterol was effectively downregulated by dietary cholesterol (1% w/w) in all three strains. In contrast, dietary cholesterol increased both hepatic LDL receptor activity and mass in the young Wistar rats and had no effect on either receptor activity or mass in the older Sprague-Dawley rats. Increases in receptor activity occurred despite increases in hepatic cholesterol especially when cholic acid was added to the cholesterol diet. The effect was systemic because CL 277082, an inhibitor of intestinal cholesterol absorption, prevented the increase in LDL receptor activity.(ABSTRACT TRUNCATED AT 250 WORDS)
Collapse
Affiliation(s)
- P D Roach
- CSIRO Australia Division of Human Nutrition, Adelaide
| | | | | | | | | | | | | |
Collapse
|
92
|
Abstract
The mechanisms of action and selected agents for a variety of approaches to the treatment of atherosclerosis have been reviewed. In Table I, each approach is listed according to its primary physiological effect. This is a simplification, of course, and some agents, such as ACAT inhibitors, may have primary effects in all of these categories. As one goes from left to right, the benefit of each physiological effect becomes more speculative. There is no question of the benefit of LDL reduction, but less evidence exists for the clinical benefits of HDL elevation. With regard to direct anti-atherosclerotic effects, most approaches have yet to gather clinical data of any type. Perhaps as a result, the degree of medicinal chemistry effort in each area to date declines as one goes from left to right. This situation is changing rapidly, however. As evidence supporting the HDL hypothesis accumulates and knowledge of how to elevate HDL levels grows, very exciting opportunities for medical advances present themselves. Likewise, the knowledge base for nonlipid intervention is growing and very rapid advances are being achieved with the plaque-imaging techniques needed for evaluating such agents in man. Such results can only lead to greater opportunities for pharmacological intervention. Thus, in the future, much greater research effort will likely be dedicated to HDL elevation and nonlipid approaches. Through these efforts, physicians of the future should be armed with several complementary agents that can reduce the risk of cardiovascular disease in all patient populations.
Collapse
Affiliation(s)
- P A McCarthy
- Medicinal Chemistry Department, Central Research, Pfizer, Inc., Groton, CT 06340
| |
Collapse
|
93
|
Sviridov D, Safonova I, Nano J, Pavlov M, Rampal P, Repin V, Smirnov V. New model to study cholesterol uptake in the human intestine in vitro. J Lipid Res 1993. [DOI: 10.1016/s0022-2275(20)40760-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
|
94
|
In vivo evidence that the lipid-regulating activity of the ACAT inhibitor CI-976 in rats is due to inhibition of both intestinal and liver ACAT. J Lipid Res 1993. [DOI: 10.1016/s0022-2275(20)40755-2] [Citation(s) in RCA: 127] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
|
95
|
Maechler P, Wollheim CB, Bentzen CL, Niesor E. Role of the intestinal acyl-CoA:cholesterol acyltransferase activity in the hyperresponse of diabetic rats to dietary cholesterol. J Lipid Res 1992. [DOI: 10.1016/s0022-2275(20)41402-6] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
|
96
|
Krause BR, Bousley RF, Kieft KA, Stanfield RL. Effect of the ACAT inhibitor CI-976 on plasma cholesterol concentrations and distribution in hamsters fed zero- and low-cholesterol diets. Clin Biochem 1992; 25:371-7. [PMID: 1490301 DOI: 10.1016/0009-9120(92)80020-h] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The overall objective of the present study was to determine if the ACAT inhibitor CI-976 can lower plasma cholesterol in hamsters fed zero or low, "human-like" levels of cholesterol. With a purified diet containing zero dietary cholesterol, CI-976 significantly lowered VLDL cholesterol (VLDL-C), but not total plasma cholesterol (TPC). When 0.06% cholesterol was added to this diet, reductions in both VLDL and LDL cholesterol (LDL-C) lowered TPC. Efficacy was still greater with 0.2% dietary cholesterol, but not potency. Mixing CI-976 into the purified diet resulted in greater decreases in VLDL-C compared to gavage administration, but LDL-C reductions with 0.2% cholesterol were optimal with gavage. With nonpurified, chow-based diets efficacy was markedly greater with diet-admix administration, regardless of the amount of dietary cholesterol. CI-976 inhibited cholesterol absorption with chow-based diets more potently compared to nonabsorbable agents (e.g., beta-sitosterol, tigogenin cellobioside), and the lowering of LDL-C was greatest when inhibition of cholesterol absorption was maximal. We conclude that the ACAT inhibitor CI-976 is efficacious in hamster models which utilize human-like levels of dietary cholesterol. Moreover, the data suggest that the pharmacologic responses to lipophilic ACAT inhibitors in the hamster, or even other lipid-regulating drugs, are likely to depend not only on the type of basal diet but also on the mode of drug administration.
Collapse
Affiliation(s)
- B R Krause
- Department of Pharmacology, Parke-Davis Pharmaceutical Division, Warner-Lambert Company, Ann Arbor, MI 48105
| | | | | | | |
Collapse
|
97
|
Bell FP, Gerrity RG. Evidence for an altered lipid metabolic state in circulating blood monocytes under conditions of hyperlipemia in swine and its implications in arterial lipid metabolism. ARTERIOSCLEROSIS AND THROMBOSIS : A JOURNAL OF VASCULAR BIOLOGY 1992; 12:155-62. [PMID: 1543690 DOI: 10.1161/01.atv.12.2.155] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Circulating blood monocytes were isolated from normal and hypercholesterolemic swine, and the monocyte lipid compositions and lipid biosynthesis profiles were assessed. The data indicate that monocytes freshly isolated from hyperlipemic swine have increased phospholipid and cholesterol contents and have increased biosynthetic capability for synthesizing phospholipids, triglycerides, and cholesteryl esters, but not cholesterol. The profile of the stimulated lipid synthesis capability is similar to that of the swine aortic intima undergoing atherogenic change. These studies indicate that circulating blood monocytes in hyperlipemic swine, which are known to give rise to intimal foam cells in the early fatty streak lesion, can contribute to altered vessel lipid metabolism without a requirement for in situ modification by wall factors.
Collapse
Affiliation(s)
- F P Bell
- Metabolic Diseases Research Upjohn Company, Kalamazoo, Mich. 49001
| | | |
Collapse
|
98
|
Bell FP, Gammill RB, St John LC. U-73482: a novel ACAT inhibitor that elevates HDL-cholesterol, lowers plasma triglyceride and facilitates hepatic cholesterol mobilization in the rat. Atherosclerosis 1992; 92:115-22. [PMID: 1632844 DOI: 10.1016/0021-9150(92)90270-q] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
U-73482, a novel acylCoA:cholesterol acyltransferase (ACAT) inhibitor with systemic activity, has been evaluated for its effects on a variety of lipid metabolic parameters in the rat. The compound inhibits ACAT in vitro in cultured Fu5AH rat hepatoma cells and demonstrates systemic activity through inhibition of hepatic ACAT in rats receiving the drug orally. U-73482 also lowers plasma triglycerides at 40 mg/kg per day in the rat and elevates high density lipoprotein cholesterol (HDL-chol) in a dose-related fashion over the range of daily intakes of 0-40 mg/kg in the rat. Elevations in HDL-chol are followed by elevations in total plasma cholesterol in normal rats but the compound exerts hypocholesterolemic activity in cholesterol-fed rats and promotes clearance of stored hepatic sterol in rats pretreated with a hypercholesterolemic diet and then changed over to normal chow. The triglyceride-lowering and HDL-chol elevating effects of U-73482 coupled with its ability to promote tissue sterol clearance and block the hypercholesterolemic effects of dietary cholesterol in animals, suggests that the compound has potential as a therapeutic agent for treatment of lipid disorders in man.
Collapse
Affiliation(s)
- F P Bell
- Upjohn Laboratories, Kalamazoo, MI 49001
| | | | | |
Collapse
|
99
|
Tabas I, Beatini N, Chen LL, Su WC, Puar MS, Dugar S, Clader JW. Identification and characterization of an acyl-CoA:triterpene acyltransferase activity in rabbit and human tissues. J Lipid Res 1991. [DOI: 10.1016/s0022-2275(20)41654-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
|
100
|
Sliskovic DR, White AD. Therapeutic potential of ACAT inhibitors as lipid lowering and anti-atherosclerotic agents. Trends Pharmacol Sci 1991; 12:194-9. [PMID: 1862535 DOI: 10.1016/0165-6147(91)90546-5] [Citation(s) in RCA: 160] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Hypercholesterolemia is one of the few independent risk factors definitively linked to increased morbidity and mortality due to myocardial infarction. One possible therapy of current interest is the prevention of the absorption of dietary cholesterol by inhibiting the enzyme, acyl-CoA: cholesterol acyltransferase (ACAT), which catalyses the intracellular formation of cholesterol esters. Evidence is now accumulating that suggests that ACAT inhibition may not only lower plasma cholesterol levels, but may also have a direct effect at the artery wall, where ACAT has been shown to be responsible for the accumulation of cholesterol esters in arterial lesions. Drago Sliskovic and Andrew White discuss the importance of ACAT in the lipid transport system and the consequences of its inhibition in a variety of tissues, with emphasis on both lipid-lowering and anti-atherosclerotic effects.
Collapse
Affiliation(s)
- D R Sliskovic
- Department of Chemistry, Parke-Davis Pharmaceutical Research Division, Warner-Lambert Company, Ann Arbor, MI 48105
| | | |
Collapse
|