Potent Hypocholesterolemic Agent Research Articles

Design, synthesis, molecular docking, ADMET studies, and biological activity evaluation of new 2-({[3-aryl-1,2,4-oxadiazol-5-yl)methyl]thio}-1H-benzimidazoles and 6-amino-6-aryl-5,6-dihydro[1,6,2,4]oxathiadiazocino[4,5-a]benzimidazol-3(2H)-ones

Aryl amidoximes are active binucleophilic compounds used as a powerful and versatile reagent in synthesizing diverse heterocyclic compounds with pharmacological interest. Thus, a new series of 2-({[3-aryl-1,2,4-oxadiazol-5-yl)methyl]thio}-1H-benzimidazoles 5a-g was successfully synthesized from the reaction of (1,3-benzimidazol-2-ylthio)acetic acid (2) with aryl amidoximes 4a-g, respectively. The reaction is proceeded in dimethylformamide (DMF) in the presence of 1,1′-carbonyldiimidazole (CDI) as a coupling reagent. The unexpected products 6-amino-6-aryl-5,6-dihydro[1,6,2,4]oxathiadiazocino[4,5-a]benzimidazol-3(2H)-one 6a-c were formed through the reaction of acetic acid derivative 2 with arylamidoxime 4b,c,g in acetonitrile at room temperature or under reflux, using CDI as coupling reagent. Compounds 5g and 6a proved the most potent hypocholesterolemic agents, with significant hypolipidemic and hypotriglyceridemic influence. They represent promising candidates for establishing novel hypolipidemic derivatives and anti-atherosclerotic. Compounds 5g and 6a demonstrated the highest antioxidant effect, reaching 77 and 81% radical scavenging activity, respectively. Docking studies were also performed on the synthesized members to examine their binding interactions with their target enzyme, Niemann-Pick C1-like 1 (NPC1L1). Finally, physicochemical properties of the synthesized compounds were investigated in silico. The obtained results showed that most synthesized members had a positive drug-likeness profile.

Evaluation of the effects of natural isoquinoline alkaloids on low density lipoprotein receptor (LDLR) and proprotein convertase subtilisin/kexin type 9 (PCSK9) in hepatocytes, as new potential hypocholesterolemic agents

Nine different isoquinoline alkaloids, berberine, govaniadine, stylopine, adlumine, adlumidine, bicuculline, sanguinarine, protopine and californidine have been evaluated for their effects on a cellular model of hepatocyte for their effect on low density lipoprotein receptor (LDLR) and proprotein convertase subtilisin/kexin type 9 (PCSK9) expression compared to simvastatin. Berberine, californidine and govaniadine induced LDLR with an effect similar to 2.5 µM simvastatin. Californidine and berberine at tested doses reduced the expression of PCSK9, with an opposite behaviour to simvastatin on this target. Govaniadine, on the other hand, showed a statin-like effect, although less potently, by increasing both LDLR and PCSK9 levels. Berberine californidine and govaniadine were then tested on the same cellular model to assess possible effect of reduction of total cholesterol, compared to simvastatin. All compounds were able to reduce total cholesterol level in the hepatocytes.

Wet Extraction of γ-Oryzanol From Rice Bran

γ-oryzanol is unique to rice bran oil (RBO) and it is known to be a potent hypocholesterolemic agent. Separation and isolation of γ-oryzanol from crude RBO is difficult due to complexity of components in crude RBO. Converting acylglycerides and FFA in RBO into FAME will concentrate bioactive compounds in the residue after FAME was removed from the RBO-based biodiesel. In this study, wet-extraction of bioactive compound from rice bran, γ-oryzanol, has been carried out using subcritical water-methanol mixture. The effects of extraction temperature, extraction time, water-methanol volume ratio and pressurizing gas type on the content and recovery of γ-oryzanol in crude RBO-based biodiesel have been investigated. It was found that the content and recovery of γ-oryzanol in RBO-based biodiesel increased with higher extraction temperature, longer extraction time and lower water concentration. The content of γ-oryzanol in RBO-based biodiesel was higher under N2 atmosphere since CO2 can acidify the solvent leading to hydrolysis of γ-oryzanol. The maximum γ-oryzanol content in RBO-based biodiesel was 2.16 % (corresponding to 2750 mg γ-oryzanol/kg rice bran) obtained after extraction for 7 h at 200 °C and 40 bar with water concentration of 50 % (v/v) under N2 atmosphere.

Psyllium Husk (Plantago ovata) as a Potent Hypocholesterolemic Agent in Animal, Human and Poultry

Psyllium Husk (Plantago ovata) as a Potent Hypocholesterolemic Agent in Animal, Human and Poultry

Hypolipidemic, antioxidant and anti-atherosclerogenic effects of aqueous extract of Zanthoxylum heitzii stem bark in diet-induced hypercholesterolemic rats.

To evaluate anti-dyslipidemic, antioxidant and anti-atherosclerogenic properties of this extract in diet-induced hypercholesterolemic rat, a model of metabolic syndrome-induced atherosclerosis and associated cardiovascular diseases. Normocholesterolemic (NC) male rats were divided into six groups (n=10) and fed a high-cholesterol (HC) diet for 30 days (5 groups), or normal rat chow (normal control group). Rats given a HC diet also received distilled water (disease control), the potent hypocholesterolemic agent with anti-atherosclerotic activity atorvastatin (2 mg/kg, positive control), or one of the three doses of Zanthoxylum heitzii stem bark aqueous extract tested (225, 300 and 375 mg/kg) concomitantly for four months. Signs of general toxicity, body temperature and weight, and water and food intake were monitored in live animals. After sacrifice, lipid profiles and oxidative stress markers were assessed in the blood and liver, aorta, and feces, and histopathological analysis of aorta was performed. Plant extract prevented the elevation of aortic total cholesterol and triglycerides, and hepatic low density lipoprotein, very low density lipoprotein, and total cholesterol. Lipid peroxidation (TBARS) was decreased and aortic atherosclerotic plaque formation prevented. These observations strongly suggest that stem bark aqueous extract of Zanthoxylum heitzii has anti-atherosclerogenic properties, at least partly mediated by antioxidant and hypolipidemic effects.

Comparative gene expression profiles induced by PPARγ and PPARα/γ agonists in rat hepatocytes

Species-differential toxic effects have been described with PPARα and PPARγ agonists between rodent and human liver. PPARα agonists (fibrates) are potent hypocholesterolemic agents in humans while they induce peroxisome proliferation and tumors in rodent liver. By contrast, PPARγ agonists (glitazones) and even dual PPARα/γ agonists (glitazars) have caused idiosyncratic hepatic and nonhepatic toxicities in human without evidence of any damage in rodent during preclinical studies. The mechanisms involved in such differences remain largely unknown. Several studies have identified the major target genes of PPARα agonists in rodent liver while no comprehensive analysis has been performed on gene expression changes induced by PPARγ and dual PPARα/γ agonists. Here, we investigated transcriptomes of rat hepatocytes after 24 h treatment with two PPARγ (troglitazone and rosiglitazone) and two PPARα/γ (muraglitazar and tesaglitazar) agonists. Although, hierarchical clustering revealed a gene expression profile characteristic of each PPAR agonist class, only a limited number of genes was specifically deregulated by glitazars. Functional analyses showed that many genes known as PPARα targets were also modulated by both PPARγ and PPARα/γ agonists and quantitative differences in gene expression profiles were observed between these two classes. Moreover, most major genes modulated in rat hepatocytes were also found to be deregulated in rat liver after tesaglitazar treatment. Taken altogether, these results support the conclusion that differential toxic effects of PPARα and PPARγ agonists in rodent liver do not result from transcriptional deregulation of major PPAR target genes but rather from qualitative and/or quantitative differential responses of a small subset of genes.

Tocotrienols inhibit lipopolysaccharide-induced pro-inflammatory cytokines in macrophages of female mice

BackgroundInflammation has been implicated in cardiovascular disease, and the important role of proteasomes in the development of inflammation and other macrophage functions has been demonstrated. Tocotrienols are potent hypocholesterolemic agents that inhibit β-hydroxy-β-methylglutaryl coenzyme A reductase activity, which is degraded via the ubiquitin-proteasome pathway. Our objective was to evaluate the effect of tocotrienols in reducing inflammation. Lipopolysaccharide (LPS) was used as a prototype for inflammation in murine RAW 264.7 cells and BALB/c female mice.ResultsThe present results clearly demonstrate that α-, γ-, or δ-tocotrienol treatments inhibit the chymotrypsin-like activity of 20 S rabbit muscle proteasomes (> 50%; P < 0.05). Chymotrypsin, trypsin, and post-glutamase activities were decreased > 40% (P < 0.05) with low concentrations (< 80 μM), and then increased gradually with concentrations of (80 - 640 μM) in RAW 264.7 whole cells. Tocotrienols showed 9 - 33% (P < 0.05) inhibitions in TNF-α secretion in LPS-stimulated RAW 264.7 cells. Results of experiments carried out in BALB/c mice demonstrated that serum levels of TNF-α after LPS treatment were also reduced (20 - 48%; P < 0.05) by tocotrienols with doses of 1 and 10 μg/kg, and a corresponding rise in serum levels of corticosterone (19 - 41%; P < 0.05) and adrenocorticotropic hormone (81 - 145%; P < 0.02) was observed at higher concentrations (40 μM). Maximal inhibition of LPS-induced TNF-α was obtained with δ-tocotrienol (10 μg/kg). Low concentrations of δ-Tocotrienols (< 20 μM) blocked LPS-induced gene expression of TNF-α, IL-1β, IL-6 and iNOS (> 40%), while higher concentrations (40 μM) increased gene expression of the latter in peritoneal macrophages (prepared from BALB/c mice) as compared to control group.ConclusionsThese results represent a novel approach by using natural products, such as tocotrienols as proteasome modulators, which may lead to the development of new dietary supplements of tocotrienols for cardiovascular diseases, as well as others that are based on inflammation.

Hypocholesterolemic Effects of Nutraceuticals Produced from the Red Microalga Porphyridium sp. in Rats

Red microalgae contain functional sulfated polysaccharides (containing dietary fibers), polyunsaturated fatty acids, zeaxanthin, vitamins, minerals, and proteins. Studies in rat models support the therapeutic properties of algal biomass and isolated polysaccharides. Algal products incorporated into rat diets were found to significantly improve total serum cholesterol, serum triglycerides, hepatic cholesterol levels, HDL/LDL ratios and increased fecal excretion of neutral sterols and bile acids. Morphological and metabolic changes were induced by consumption of algal products. These results suggest that red microalgae can be used as potent hypocholesterolemic agents, and they support the potential use of red microalgae as novel nutraceuticals.

Synthesis and HMG CoA reductase inhibition of 4-thiophenyl quinolines as potential hypocholesterolemic agents

A series of novel 4-thiophenyl quinoline-based mevalonolactone derivatives were synthesized from ethyl 6,7,8-trisubstituted-4-chloro-quinoline-3-carboxylates by several reactions and evaluated for their ability to inhibit the rat HMG CoA reductase in vitro. It was found that substitution with a variety of thiophenyl groups at position 4 in quinoline resulted in retention or enhancement of the inhibition and the preferable groups were 4-isopropyl-thiophenyl and 3-methoxy-thiophenyl. (4 R,6 S)-6-[( E)-2-(6,7,8-trifluoro-4-isopropylthiophenyl-quinoline-3-yl)-ethenyl]-3,4,5,6-tetrahydro-4-hydroxy-2 H-pyran-2-one ( A16) and (4 R, 6 S)-6-[( E)-2-(6-fluoro-4,7-di-(3-methoxy-thiophenyl)-quinoline-3-yl)-ethenyl]-3,4,5,6-tetrahydro-4-hydroxy-2 H-pyran-2-one ( A23) were approximately three times more potent than rosuvastatin or pitavastatin in inhibiting HMG CoA reductase and selected as the hypocholesterolemic candidates for further evaluation.

Molecular docking of the highly hypolipidemic agent α-asarone with the catalytic portion of HMG-CoA reductase

Docking experiments using a number of published crystal structures of HMG-CoA reductase with the potent hypocholesterolemic agent α-asarone are described. The results indicate that α-asarone binds in the enzyme’s active site. The methoxy groups play a key role in the binding and probably also in its biological activity, as shown by extensive SAR studies reported for analogues of α-asarone. The docking results will be valuable for the structure-based design of novel hypolipidemic agents.

A Glucomannan and Chitosan Fiber Supplement Decreases Plasma Cholesterol and Increases Cholesterol Excretion in Overweight Normocholesterolemic Humans

Objective: Both chitosan and glucomannan have demonstrated hypocholesterolemic effects. A recent study in rats indicates that the combination of the two is also a potent hypocholesterolemic agent that increases fecal fat excretion. The objective of the present study was to determine the hypocholesterolemic effect of a supplement containing equal amounts of chitosan and glucomannan on blood lipid concentrations and fecal excretion of fat, neutral sterols and bile acids.Methods: Twenty-one overweight normocholesterolemic subjects (11 males and 10 females) were fed 2.4 g/day of a supplement containing equal amounts of chitosan and glucomannan. Prior to taking the supplement (initial period) and after 28 days (final period), blood was drawn for measurement of serum lipids and a three-day fecal sample collected for determination of fat, neutral sterol and bile acid excretion. Subjects maintained their normal dietary and activity patterns during the study.Results: Caloric intake and intake of fat and dietary fiber (excluding the supplement) did not differ between the initial and final periods. Serum total, HDL and LDL cholesterol concentrations were significantly lower (p < 0.05) in the final period compared to the initial period. Serum triacylglycerol concentration did not change between periods. There was a trend towards greater fecal excretion of neutral sterols and bile acids (p = 0.13 and 0.16, respectively) in the final period. However, fecal fat excretion did not differ between periods.Conclusions: Serum cholesterol reduction by a chitosan/glucomannan supplement is likely mediated by increased fecal steroid excretion and is not linked to fat excretion.

Regulation of PUFA metabolism: pharmacological and toxicological aspects

Levels of the long-chain polyunsaturated fatty acids (LCP) of the n-6 and n-3 series in animal plasma and cells are directly or indirectly dependent upon the intakes of either their precursors, the short-chain polyunsaturated fatty acids (SCP), linoleic (LA, 18:2 n-6) and alpha linolenic acid (ALA, 18:3 n-3), respectively, and/or of the preformed products (arachidonic, 20:4 n-6) and eicosapentaenoic acid (EPA, 20:5 n-3) and docosahexaenoic acid (DHA, 22:6 n-3). We report here that pharmacological agents and cytotoxic compounds significantly affect the production of LCP from SCP in cultured cells. Using labelled substrates and radio HPLC separations, we observed that the potent hypocholesterolemic agent, simvastatin, activates the formation of AA from LA, mainly acting at the Δ5 desaturation step, and increases also the mRNA levels, in cultured monocytic cells (THP-1). Elevation of AA occurs also in plasma lipids of hyperlipemic patients treated with statins (but not with fibrates). Conversely, oxysterols (mainly 7-β-oxysterol), which are detected in circulating lipoproteins of rabbits on a hypercholesterolemic diet, potently inhibit the synthesis of AA from LA in hepatocytic cell lines (Hep-G2). At the same time plasma levels o AA are reduced vs controls, in spite of an identical intake of LA. Finally, on the basis of previous work showing reduced levels of LCP, mainly DHA, in the milk of cigarette-smoking mothers, we have observed that the incubation of human mammary gland cells with sera exposed to cigarette smoke results in marked inhibition of the production of DHA from ALA. The products in smoke responsible for this effect, are being identified through mass spectrometric techniques. In conclusion, pharmacological agents and toxic compounds, such as oxysterols and smoke products affect key steps in the synthesis of the LCP, major bioregulators in mammalian cells.

The combined effects of novel tocotrienols and lovastatin on lipid metabolism in chickens

Both lovastatin (a fungal product) and a tocotrienol rich fraction (TRF 25, a mixture of tocols isolated from stabilized and heated rice bran containing desmethyl [ d-P 21-T3] and didesmethyl [ d-P 25-T3] tocotrienols) are potent hypocholesterolemic agents, although they suppress cholesterol biosynthesis by different mechanisms. To determine additive and/or synergistic effects of both agents, chickens were fed diets supplemented with 50 ppm TRF 25 or d-P 25-T3 in combination with 50 ppm lovastatin for 4 weeks. Combinations of d-P 25-T3 with lovastatin were found most effective in reducing serum total cholesterol and low-density lipoprotein (LDL) cholesterol compared to the control diet or individual supplements. The mixture of TRF 25+lovastatin inhibited the activity of β-hydroxy- β-methylglutaryl coenzymeA reductase (21%) compared to lovastatin alone, which did not change its activity. Cholesterol 7 α-hydroxylase activity was increased by lovastatin (11%) and by lovastatin plus TRF 25 (19%). TRF 25+lovastatin decreased levels of serum total cholesterol (22%), LDL cholesterol (42%), apolipoprotein B (13–38%), triglycerides (19%), thromboxane B 2 (34%) and platelet factor 4 (26%), although high-density lipoprotein (HDL) cholesterol, and apolipoprotein A1 levels were unaffected. The mixture of TRF 25+lovastatin showed greater effects than did the individual treatments alone, reflecting possible additive pharmacological actions. The effects, however, of the d-P 25-T3/lovastatin combination were no greater than that of d-P 25-T3 alone, possibly indicating that d-P 25-T3 produced a maximum cholesterol lowering effect at the concentration used.

Effect of hypocholesterolemic doses of 17 alpha-ethinyl estradiol on cholesterol balance in liver and extrahepatic tissues.

This study was performed to investigate the effects of 17 alpha-ethinyl estradiol, a potent hypocholesterolemic agent at pharmacological doses, on cholesterol balance in the liver and extrahepatic tissues of the rat in vivo. Female Sprague-Dawley rats were treated with 17 alpha-ethinyl estradiol (5 mg/kg per day s.c. for 5 days) or with 4-aminopyrazolo(3,4-d) pyrimidine (20 mg/kg per day i.p. for 3 days). Both drug regimens suppressed plasma total and low density lipoprotein-cholesterol by more than 80%. Analysis of the kinetic parameters of low density lipoprotein transport did not show increased receptor activity in extrahepatic tissues during either treatment. 17 alpha-Ethinyl estradiol significantly increased low density lipoprotein tissue spaces and clearance rates in the liver, with a 5-fold increase in low density lipoprotein-receptor activity, whereas 4-aminopyrazolo(3,4-d)pyrimidine suppressed hepatic transport of low density lipoprotein probably due to a nospecific toxic effect. Treatment with 17 alpha-ethinyl estradiol markedly enhanced the hepatic expression of low density lipoprotein-receptor protein and mRNA despite a 7-fold increase in hepatic cholesteryl ester levels. Finally, treatment with both drugs increased cholesterol synthesis in several extrahepatic tissues, such as adrenals, ovaries, small bowel, and spleen. These findings confirm that 17 alpha-ethinyl estradiol at pharmacological doses markedly increases synthesis and expression of low density lipoprotein-receptor in the liver. Hypocholesterolemia, whether induced by activation of low density lipoprotein-receptors or by other mechanisms, fails to up-regulate low density lipoprotein transport in extrahepatic tissues, which rather respond by increasing local sterol synthesis. This suggests the occurrence of separate regulatory mechanisms for low density lipoprotein transport and cholesterol synthesis.

Synthesis and biological evaluation of a new series of sterols as potential hypocholesterolemic agents.

A new series of sterols was synthesized and tested in a CHO cell-based LDL receptor/luciferase (LDLR/Luc) assay to investigate the capability of derepressing the transcription of LDL receptor promoter in the presence of 25-hydroxycholesterol. The effect of various substitutions on antagonizing the repressing effect mediated by 25-hydroxycholesterol was also studied in terms of regio- and stereochemistry, lipophilicity, steric bulk, and pi-electron density. Except 12, compounds active in the primary LDLR/Luc assay were not active in the secondary simian virus 40/luciferase (SV40/Luc) assay, demonstrating the specificity of their in vitro activity. Eight active compounds of various structural types were selected and screened in a [1-14C-acetate]cholesterol biosynthesis inhibition assay; none has shown any interference with the cholesterol biosynthesis in CHO cells. In hypercholesterolemic hamsters, generally, compounds that were active in vitro were active in vivo and vice versa, with the exception of three in vitro inactive compounds: 3 beta-ols 3a' and 3c' as well as 3-ketone 2a. Experimental results from the livers of hamsters revealed that the in vivo conversion of 3a' or 2a to 3a has in part contributed to the observed in vivo activity, and it is also anticipated that 3c' may similarly be converted to 3c in hamsters.

Inhibitors of Sterol Synthesis: 3β-Hydroxy-25,26,26,26,27,27,27-heptafluoro-5α-cholestan-15-one, an Analog of a Potent Hypocholesterolemic Agent in Which Its Major Metabolism Is Blocked

The chemical synthesis of 3β-hydroxy-25,26,26,26,27,27,27-heptafluoro-5α-cholestan-15-one ( IV) has been pursued to provide an analog of the potent hypocholesterolemic agent 3β-hydroxy-5α-cholest-8(14)-en-15-one ( I) in which its major metabolism is blocked. Reduction of 3β-acetoxy-5α-chola-8(14),23-dien-15-one with lithium in liquid ammonia gave 3β-hydroxy-5α-chol-23-en-15-one ( VI). Addition of (CF 3) 2CFI to VI in the presence of triethyl borane gave 3β-hydroxy-23R-iodo-25,26,26,26,27,27,27-heptafluoro-5α-cholestan-15-one, which was reduced to IV with tributyltin hydride. IV was found to be highly active in lowering the levels of HMG-CoA reductase activity in CHO-K1 cells, in lowering acyl coenzyme A:cholesterol acyltransferase activity in jejunal microsomes, and in lowering serum cholesterol levels in rats.

ChemInform Abstract: Inhibitors of Acyl‐CoA:Cholesterol Acyltransferase. Part 4. A Novel Series of Urea ACAT Inhibitors as Potential Hypocholesterolemic Agents

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Inhibitors of acyl-Coa:cholesterol acyltransferase. 4. A novel series of urea ACAT inhibitors as potential hypocholesterolemic agents.

We have synthesized a series of N-phenyl-N'-aralkyl and N-phenyl-N'-(1-phenylcycloalkyl)ureas as inhibitors of acyl-CoA:cholesterol acyltransferase (ACAT). This intracellular enzyme is thought to be responsible for the esterification of dietary cholesterol; hence inhibition of this enzyme could reduce diet-induced hypercholesterolemia. For this series of compounds, the in vitro ACAT inhibitory activity was improved by increasing the bulk of the 2,6-substituents on the phenyl ring. Additionally, we found that spacing of the aromatic rings was critical for ACAT inhibitory activity. A phenyl ring five atoms away from the requisite 2,6-diisopropylphenyl moiety was optimal for in vitro activity. Substitution alpha to the N'-phenyl moiety enhanced in vitro potency. In the case of phenylcycloalkyl ureas, ACAT inhibitory activity was independent of the size of the cycloalkyl ring. From this series of analogs, compound 25, which had excellent in vitro potency for inhibiting ACAT, was found to lower plasma cholesterol by 73% in vivo when administered in the diet at 50 mg/kg in an animal model of hypercholesterolemia. In this model, compound 25 lowered plasma cholesterol dose dependently and was as efficacious as the Lederle ACAT inhibitor CL 277082.

Effects of pravastatin on cholesterol metabolism in Watanabe heritable hyperlipidemic rabbits.

Pravastatin, a competitive inhibitor of hydroxymethylglutaryl CoA reductase (HMG CoA reductase) is a potent hypocholesterolemic agent in humans as well as experimental animals, including the Watanabe heritable hyperlipidemic (WHHL) rabbit, lacking low density lipoprotein (LDL) receptor activity. We studied the effect of pravastatin on several aspects of cholesterol metabolism in WHHL rabbits. Cholesterol synthesis was measured by intraperitoneal injection of radioacetate and determination of its incorporation into the nonsaponifiable lipid fraction of liver, plasma, adrenal glands and gonads. A single dose of pravastatin (25 mg/kg) caused statistically significant inhibition of hepatic cholesterol synthesis at 2, 6, 12, and 24 hours following oral administration. By 48 hours, the inhibitory effect of the drug was no longer demonstrable. The pattern of radioactivity in the plasma was similar to that in the liver. The drug had no statistically significant effect on cholesterol synthesis in adrenal glands and gonads, suggesting a selective effect on the liver. Cholesterol absorption was studied after simultaneous oral administration of [3H] cholesterol and [14C] beta-sitosterol. Pravastatin, 50 mg/kg for 10 days had no effect on fecal excretion of the radiolabelled steroids over 4 days. At 24 hours the plasma level of [14C] cholesterol was 1/3 that of control in pravastatin treated animals (p < 0.05) but did not undergo an accelerated decline over 6 days. The activity of acyl CoA: cholesterol acyltransferase (ACAT) in intestinal mucosa and the concentration of hepatic cholesterol were similar in animals treated over one year with pravastatin 50 mg/kg/day or with placebo. Our data do not allow us to make definitive conclusions about the effect of pravastatin on cholesterol absorption but are compatible with the hypothesis that the drug inhibits the hepatic synthesis as well as the assembly of cholesterol into lipoproteins.

Inhibitors of 3-hydroxy-3-methylglutaryl coenzyme A reductase induce reductase accumulation and altered lamellar bodies in rat forestomach keratinocytes.

Lovastatin, an inhibitor of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase and a potent hypocholesterolemic agent, induces a hyperplastic thickening of the rat forestomach mucosa after oral administration of its active form, a hydroxyacid. We studied the effects of lovastatin on the intracellular accumulation of HMG-CoA reductase immunostaining and the accompanying morphological changes in rat forestomach keratinocytes by immunofluorescence microscopy and transmission electron microscopy (TEM). Administration of lovastatin hydroxyacid induced increases in HMG-CoA reductase levels within forestomach keratinocytes that were dose and time dependent and reversible. The adjacent glandular stomach epithelium did not exhibit induction of reductase. A pharmacologically inactive epimer of lovastatin hydroxyacid did not increase keratinocyte reductase accumulation, and lovastatin lactone induced minimal forestomach reductase. TEM of forestomachs from rats given lovastatin hydroxyacid demonstrated profound alterations in epidermal lamellar bodies (organelles that transport lipids and steroids to the intercellular spaces of the stratum corneum). Treated cells lacked internal lipid lamellae and failed to secrete sheets of lipid material into the intercellular spaces of the stratum corneum. We hypothesize that sustained inhibition of HMG-CoA reductase in rat forestomach keratinocytes induces accumulation of HMG-CoA reductase and hyperplasia by inhibiting sterol synthesis, assembly of lamellar bodies, and formation of intercellular lipid sheets.