Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “CASEIN”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 487 records · Page 27Linked to original sources
PubMed1995

Characterization of multiply phosphorylated peptides selectively precipitated from a pancreatic casein digest.

Anticariogenic phosphopeptides, released during the hydrolysis of casein with trypsin, contain the cluster sequence Ser(P)-Ser(P)-Ser(P)-Glu-Glu and have commercial potential as toothpaste, mouthwash, and food additives for the prevention of dental caries. To develop a commercial-scale process for the production of these peptides, we have comprehensively characterized casein phosphopeptides that were selectively precipitated using Ca2+ and ethanol from an acid-clarified (pH 4.6) pancreatic casein hydrolysate. Casein was hydrolyzed using pancreatin at 50 degrees C for 2 h. The precipitate contained a series of casein phosphopeptides that were slightly truncated relative to tryptic casein phosphopeptides. The major casein phosphopeptides released by pancreatin were beta-CN-4P(f7-24), alpha s1-CN-5P(f61-78), and alpha s1-CN-5P(f59-78), all containing the cluster sequence. The truncation of the tryptic peptides beta-CN-4P(1-25) and alpha s1-CN-5P(f59-79) resulted from the chy-motryptic and carboxypeptidase activities of the pancreatin. The peptides containing the cluster sequence constituted 77.8 +/- 6.7 mol/100 mol of the total peptides that were selectively precipitated. This composition was not significantly different from that of casein phosphopeptides produced under identical conditions using trypsin. In conclusion, pancreatin should be a suitable enzyme preparation for the production of anticariogenic casein phosphopeptides on a commercial scale.

Amino Acid Sequence↗
PubMed2001

Non-coordinate expression of closely linked mouse casein genes.

Expression levels of five mouse casein genes were analysed in the mammary gland of virgin, pregnant and lactating mice. We have already shown that the five murine casein genes are arranged in the order, alpha-beta-gamma-epsilon-kappa in a tandem array, very close to each other in a 250 kb DNA fragment of mouse genome. Northern blot analysis showed that, of the calcium-sensitive casein genes, the epsilon casein gene is expressed only during lactation unlike the alpha, beta and gamma casein genes which are expressed during pregnancy and lactation. Even though the alpha, beta and gamma genes exhibited a co-ordinated expression pattern from mid to the later stages of pregnancy, the mRNA levels varied considerably (60, 90 and 100% respectively) by the onset of lactation. The mRNA level of the calcium-insensitive kappa casein gene increased from mid-pregnancy but at a lower rate and reached approximately 60% by the first day of lactation. Considering the locations and closeness of the casein genes, a non-coordinate expression profile is exhibited by the mouse casein genes, particularly the epsilon casein gene.

Animals↗
PubMed1992

Casein kinase II and the tumor suppressor protein P53 associate in a molecular complex that is negatively regulated upon P53 phosphorylation.

Selective immunoisolation of P53 from Sf9 cells coexpressing wild-type P53 and casein kinase II yielded a preparation containing casein kinase II, thus suggesting that the two proteins may associate in a molecular complex in the intact cell. Such a complex could indeed be demonstrated in vitro between purified recombinant P53 and oligomeric casein kinase II and was shown to dissociate when P53 became phosphorylated by the kinase. This suggested that the P53 C-terminal domain, which contains the casein kinase II phosphorylation site was involved in the protein-protein interaction; this was confirmed by the fact that an anti-P53 monoclonal antibody directed to that domain inhibited the P53-casein kinase II association. Studies with isolated recombinant casein kinase II subunits disclosed that although the alpha (catalytic) subunit could phosphorylate P53, the formation of a stable P53-casein kinase II association required the presence of the beta subunit of the kinase. This was confirmed by immunoisolation of a P53-beta subunit complex from cells expressing both polypeptides. Although the biological significance of a reversible P53-casein kinase II molecular complex in the control of cell proliferation processes remains to be defined, these observations suggest the possibility of a novel mechanism regulating P53 and casein kinase II activities in the intact cell.

Adenosine Triphosphate↗
PubMedDate not supplied

Effect of different kinds of dietary casein on blood cholesterol and triglycerides in pair fed rats.

After casein intake, serum cholesterol levels are dependent on many experimental conditions in rats. The effect of the method of casein preparation was assessed in Wistar rats pair-fed for 4 wk with three identical diets differing only by the type of casein used. Compared with dietary casein and Na caseinate, ingestion of lipid- and vitamin-free casein resulted in higher liver weights (4.35 +/- 0.23 vs. 3.89 +/- 0.30 and 3.90 +/- 0.25 g) and fasting serum cholesterol levels (0.55 +/- 0.13 vs. 0.49 +/- 0.09 and 0.44 +/- 0.09 g/L). Compared with the two other casein diets, ingestion of Na caseinate produced the lowest fasting serum triglyceride levels (0.62 +/- 0.13 vs 0.74 +/- 0.12 and 0.73 +/- 0.13 g/L). Peptic digestibility of caseins used might be a regulating factor of serum cholesterol levels in Wistar rats.

Animals↗
PubMed1991

Activation of casein kinase II by sphingosine.

Sphingosine activates casein kinase II in the presence of endogenous substrates as well as a synthetic peptide substrate. The activation response occurred between 12 and 25 micrograms/ml sphingosine and exhibited positive cooperativity with a Hill coefficient of 3.0. Sphingosine not only increased the Vmax of casein kinase II but decreased the Km(app) for the peptide substrate from 0.5 to 0.08 mM. In contrast, the Km(app) for MgCl2 was increased from 0.12 to 0.7 mM. Consequently, sphingosine altered significantly several parameters which determine casein kinase II activity. The effect of sphingosine was relatively specific, inasmuch as related lipids were less potent activators or largely ineffective in stimulating casein kinase II. On the other hand, the effect of sphingosine itself could be potentiated or inhibited by other lipids. Ceramide and sphingosylphosphorylcholine augmented the sphingosine effect. Phospholipids alone did not alter the activity of casein kinase II significantly, but abolished enzyme activation by sphingosine with different potencies (phosphatidylserine greater than phosphatidylethanolamine greater than phosphatidylinositol greater than phosphatidylcholine). Moreover, the sphingosine effect could be abrogated by KCI and NaCl, which alone are known to induce enzyme activation and dissociation of aggregated casein kinase II protein; LiCl and NH4Cl also inhibited the sphingosine effect. Polyamines, known activators of casein kinase II, partially mimicked the effect of sphingosine on endogenous polypeptide phosphorylation but failed to do so with the peptide substrate. These observations demonstrate that sphingosine is a potent activator of casein kinase II. The potential pharmacological and physiological modulation of casein kinase II by sphingoid bases is discussed.

Animals↗
PubMed1990

Casein kinase II from Caenorhabditis elegans. Properties and developmental regulation of the enzyme; cloning and sequence analyses of cDNA and the gene for the catalytic subunit.

The nematode Caenorhabditis elegans provides a model system for investigating the structure, function, and regulation of casein kinase II. Cytosols from C. elegans embryos and gravid adults, which contain fertilized eggs and embryos, are enriched in casein kinase II activity; cytosols from newly hatched larva, four subsequent larval stages, and immature adults exhibit casein kinase II levels that are 3-10-fold lower than those observed in embryo cytosol. C. elegans casein kinase II contains alpha (Mr = 42,000) and beta (Mr = 29,000) subunits and has a Stokes radius of 50 nm. The enzyme utilizes ATP and GTP as substrates, is potently inhibited by heparin and undergoes autophosphorylation. Sequence analyses of cloned cDNAs corresponding to the 1.7-kilobase mRNA encoding the alpha (catalytic) subunit of casein kinase II indicate that the alpha polypeptide contains 359 amino acid residues. Variations in the abundance of casein kinase II alpha mRNA are coordinated with changes in enzyme activity during C. elegans development, indicating that alpha subunit expression is controlled at a pretranslational level. However, the magnitude of the developmentally controlled changes in phosphotransferase activity exceeded the corresponding increments in alpha subunit mRNA content. This suggests that translational and/or post-translational mechanisms also play an important role in the developmental regulation of C. elegans casein kinase II activity. The 2.9-kilobase casein kinase II alpha gene is divided into eight exons by intervening sequences ranging from 48 to 457 base pairs in length. The alpha gene promoter contains a TATA box, and a unique transcription start site has been identified. The intron/exon organization of the casein kinase II alpha gene differs markedly from the gene structure of the catalytic subunit of murine cAMP-dependent protein kinase (Chrivia, J. C., Uhler, M. D., and McKnight, G. S. (1988) J. Biol. Chem. 263, 5739-5744).

Amino Acid Sequence↗
PubMed1989

Effects of extracellular matrix on the growth and casein gene expression of primary mouse mammary tumor cells in vitro.

This study describes a serum-free culture system and provides a tumor model to investigate the effects of extracellular matrices on the growth and beta-casein gene expression of mouse mammary tumor epithelial cells (MMTCs) in vitro. Primary cultures of MMTCs derived from autochthonous mammary tumors in BALB/cfC3H x DBA/8 F1 mice, FUKU cells, an established MMTC line, and COMMA-1D cells established from mouse mammary tissues were studied. A reconstituted basement membrane from the Englbreth-Holm-Swarm tumor (Matrigel) allowed a 2.7-fold increase in cell number of 5-day primary MMTC cultures in serum-free, insulin-supplemented medium. FUKU and COMMA-1D cells in serum-free medium displayed a 13.6- and 11.5-fold increase in cell number, respectively, after 5 and 6 days in culture on Matrigel. In semisolid agar cultures, Matrigel or laminin was shown to promote colony-forming efficiency of FUKU cells when either of the matrices was mixed in the top agar layer. An increase of 4.4 or 2.1 times in colony-forming efficiency was detected when 20% (v/v) Matrigel or 112 micrograms/ml of laminin were mixed in the agar layer compared with FUKU cells plated in plain agar. beta-Casein mRNA was detectable by Northern blot assays in the primary mammary tumors. MMTCs in primary cultures grown on Matrigel in serum-free, insulin-supplemented medium for 4 days were inducible for beta-casein mRNA following the treatment with prolactin and hydrocortisone (FPRL) for 24 h. No beta-casein mRNA was detectable in the absence of FPRL. MMTCs in the primary cultures could also be induced for beta-casein mRNA when they were cultivated on type I collagen gels for 4 days but not on laminin, type IV collagen, or plastic. However, the capacity to respond to FPRL was not lost in MMTCs cultured on laminin. When MMTCs were initially cultured on laminin for 4 days and then subcultured on Matrigel for another 4 days, they were inducible for beta-casein mRNA upon exposure to FPRL for 24 h. In contrast, no beta-casein mRNA upon exposure to FPRL for 24 h. In contrast, no beta-casein mRNA was found in MMTCs from the same tumors cultured on laminin for 8 days with the same treatment of hormones. These data demonstrate that cells from autochthonous mammary tumors, which are not dependent on estrogen for growth in vivo, are inducible in vitro for beta-casein mRNA by FPRL; and this hormonal response of MMCTs requires appropriate extracellular matrix.

Animals↗
PubMed1982

Hormonal induction of casein gene expression limited to a small subpopulation of 7,12-dimethylbenz(a)anthracene-induced mammary tumor cells.

In the hormonally responsive 7,12-dimethylbenz(a)anthracene (DMBA)- or N-nitrosomethylurea (NMU)-induced mammary carcinomas, regulatory mechanisms have been altered such that these tumors retain their hormonal dependence for growth but possess only a limited ability to synthesize the mammary gland-specific milk proteins. Quantitation of casein mRNA levels revealed that very low levels of casein messenger RNA (mRNA) were expressed in both the DMBA- and NMU-induced tumors growing in virgin animals (0.1 to 0.4% of the maximally induced 8-day-lactating mammary gland). Growth of DMBA-induced tumors in pregnant rats and the treatment of NMU-induced tumor-bearing animals with thioproperazine indicated that the tumor casein mRNA levels were hormone inducible (3.4- and 2.1-fold for the DMBA- and NMU-induced tumors, respectively). However, casein mRNA levels were still only 1 to 2% of those found in the normal mammary gland under the same hormonal environment. Localization of the casein-synthesizing cells in the DMBA-induced tumors by peroxidase-antiperoxidase staining and a specific casein antiserum indicated that, in both control and hormone-treated tumors, the vast majority of cells (greater than 95%) were unstable to synthesize casein. The hormonal induction of casein mRNA sequences could be correlated with an increase in the number of cells synthesizing casein, which appeared as small clusters of cells throughout the tumors. Therefore, the loss of hormone-regulated differentiated function in these tumors, which maintained hormone-dependent growth, suggests the presence of a defective regulatory mechanism beyond the level of the hormone-receptor-complex.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1996

[HMG 14--a physiological substrate for casein kinase NII of neuronal chromatin].

The "in vivo" effects of antifeins on casein kinase NII from rat brain neuronal chromatin have been investigated. Injection of antifeins into rats resulted in changed in cAMP-independent phosphorylation of HMB 14 by casein kinase NII. No changes in HMB 17 phosphorylation were found. Casein kinase NII was isolated and purified from rat brain neuronal chromatin. It was established that casein kinase phosphorylates HMG 14 (but not HMB 17) from rat rain cells and calf thymus as effectively as do exogenous substrates, phosvitin and casein. The Km values for HMB 14 and HMB 17 from brain cells are 5.1 and 180.5 mumol, respectively. Antifeins do not influence casein kinase NII, when HMB 17, phosvitin and casein are used as substrates. HMG 14 phosphorylation changed significantly under the action of antifeins (10(-8)-10(-6) M). "In vivo" and "in vitro", some antifeins increase, and others reduce phosphorylation of HMB 14 by casein kinase NII. This correlates with their action on the transcription and long-term memory. The role of casein kinase NII and its physiological substrates in regulation of chromatin transcription is discussed.

Animals↗
PubMed1998

Antipeptide Antibodies as Analytical Tools To Discriminate among Bovine alpha(s1)-Casein Components.

Polyclonal antibodies raised against synthetic peptides reproducing sequence stretches of bovine alpha(s1)-casein were used as probes to discriminate within the alpha(s1)-casein fraction of bovine milk and cheese. A minor alpha(s1)-casein component, selectively recognized by an antisera directed against the bovine 139-149 alpha(s1)-casein sequence, was found to be a C-terminally truncated alpha(s1)-casein form. This component coeluted with the main alpha(s1)- and alpha(s2)-casein by anion-exchange chromatography of whole casein, whereas by RP-HPLC it eluted with alpha(s2)-casein only. Similarly to the main alpha(s1)-casein, the C-terminally truncated form was hydrolyzed in vitro by chymosin and early in the cheese-making.

Journal Article↗
PubMed1985

Partial Isolation and Degradation of Caseins by Cell Wall Proteinase(s) of Streptococcus cremoris HP.

The cell wall proteinase fraction of Streptococcus cremoris HP has been isolated. This preparation did not exhibit any activity due to either specific peptidases known to be located near the outside surface of and in the membrane or intracellular proteolytic enzymes. By using thin-layer chromatography for the detection of relatively small hydrolysis products which remain soluble at pH 4.6, it was shown that beta-casein is preferentially attacked by the cell wall proteinase. This was also the case when whole casein or micelles were used as the substrate. kappa-casein hydrolysis is a relatively slow process, and alpha(s)-casein degradation appeared to proceed at an extremely low rate. These results could be confirmed by using CH(3)-labeled caseins. A relatively fast and linear initial progress of CH(3)-labeled beta-casein degradation is not inhibited by alpha(s)-casein and only slightly by kappa-casein at concentrations of these components which reflect their stoichiometry in the micelles. Possible implications of beta-casein degradation for growth of the organism in milk are discussed.

Journal Article↗
PubMed1982

Electrophoretic and biochemical comparison of casein and whey protein from porcine colostrum and milk.

Porcine colostrum casein contained at least one major polypeptide band in both acid gel and sodium dodecyl sulfate gel electrophoresis that did not appear in patterns of casein prepared from porcine milk. In sodium dodecyl sulfate gel patterns, this polypeptide possessed a molecular weight of 62,000 and stained positively with "Stains-all" but not with periodic acid-Schiff reagent. Several minor caseins that appeared in acid and alkaline gel patterns from colostrum could not be detected in casein prepared from milk. Seven minor polypeptides in sodium dodecyl sulfate gel patterns of whey proteins prepared from porcine colostrum could not be detected in milk. Identical acid and alkaline gel patterns were obtained for whey proteins prepared from colostrum and milk. Only the sodium dodecyl sulfate gel electrophoretic pattern of casein prepared from milk, and possibly the alkaline gel electrophoretic pattern of whey protein prepared from milk, contained polypeptides not in patterns from colostrum. Total phosphorus contents of colostrum and milk casein were 2.96% and 3.78%. Casein prepared from porcine colostrum contained almost twice as much hexosamine and slightly elevated N-acetylneuraminic acid as casein prepared from milk. Hexose content was nearly equivalent. Whey protein prepared from milk contained more total hexose than casein prepared from colostrum, whereas N-acetylneuraminic acid and hexosamine contents were nearly equivalent.

Animals↗
PubMed1993

Hierarchical regulation by casein kinases I and II of the activation of protein phosphatase-1i by glycogen synthase kinase-3 is ionic strength dependent.

The roles of casein kinases I and II in the activation of protein phosphatase-1i (PP-1i) by glycogen synthase kinase-3 (GSK-3) were studied using enzyme preparations from porcine heart. PP-1i was activated by GSK-3 and the levels of activation achieved decreased by increasing the ionic strength (0-0.2 M KCl) in the incubation mixtures. At low ionic strength (no KCl added) casein kinase II increased the rate of activation of PP-1i by GSK-3 and the activation proceeded to a slightly greater extent (110-120%) than that obtained by GSK-3 alone. In the presence of 0.14 M KCl only a partial activation of PP-1i by GSK-3 was observed, but when casein kinase II was also added activation was restored to levels observed when PP-1i was activated by GSK-3 in the absence of salt. This effect was shown to be dependent on the concentration of casein kinase II. These results would imply that at low ionic strength casein kinase II and GSK-3 synergistically activate PP-1i as has been previously reported for the rabbit skeletal muscle enzyme (DePaoli-Roach, A. A., J. Biol. Chem. 259, 12144-12152, 1984), whereas, at physiological ionic strength, casein kinase II action may be obligatory for GSK-3 activity. Similar results were obtained when casein kinase I replaced casein kinase II.

Animals↗
PubMed1982

Isolation and solubilization of casein kinase from Golgi apparatus of bovine mammary gland and phosphorylation of peptides.

Phosphate incorporation from [gamma-32P]ATP into native and dephosphorylated alpha s1-casein is catalyzed by a casein kinase localized in the Golgi apparatus of lactating bovine mammary gland. Casein kinase from the Golgi is activated with either Mg2+ or Ca2+, and increased specific activity is observed with dephosphorylated casein as the substrate. The casein kinase can be solubilized from Golgi apparatus by the non-ionic detergent, Triton X-100. Gel permeation chromatography on Sepharose CL-4B yields a Stokes radius of 10 nm for the detergent-solubilized casein kinase. Dephosphorylated beta-peptide, the amino-terminal peptide from beta-casein, is a good substrate for the solubilized casein kinase. With dephosphorylated beta-peptide, the maximal velocity is 9.1 and 12.0 nmol/min per mg protein with Mg2+ and Ca2+ activation, respectively. The Michaelis constant for beta-peptide is greater with Ca2+ than with Mg2+ (4.8 mg/ml compared to 0.97 mg/ml). However, the Michaelis constant for ATP is not greatly influenced by these metal ions. The Triton X-100-solubilized Golgi enzyme can also catalyze the phosphorylation of peptides, such as fibrinopeptide A and alpha-melanocyte stimulating hormone.

Animals↗
PubMed1999

Epitope analysis of the multiphosphorylated peptide alpha s1-casein (59-79).

The multiphosphorylated tryptic peptide alpha(s1)-casein(59-79) has been shown to be antigenic with anti-casein antibodies. In an approach to determine the amino acyl residues critical for antibody binding we undertook an epitope analysis of the peptide using overlapping synthetic peptides. With alpha(s1)-casein(59-79) as the adsorbed antigen in a competitive ELISA only two of five overlapping synthetic peptides at 1 mM significantly inhibited binding of the anti-casein antibodies. Peptides Glu-Ser(P)-Ile-Ser(P)-Ser(P)-Ser(P)-Glu-Glu and Ile-Val-Pro-Asn-Ser(P)-Val-Glu-Glu inhibited antibody binding by 20.0+/-3.6% and 60.3+/-7.9%, respectively. The epitope of Glu63-Ser(P)-Ile-Ser(P)-Ser(P)-Ser(P)-Glu-Glu70 was further localised to the phosphoseryl cluster as the peptide Ser(P)-Ser(P)-Ser(P) significantly inhibited binding of the anti-casein antibodies to alpha(s1)-casein(59-79) by 29.5+/-7.4%. Substitution of Ser(P)75 with Ser75 in the second inhibitory peptide Ile-Val-Pro-Asn-Ser(P)75-Val-Glu-Glu also abolished inhibition of antibody binding to x(s1)-casein (59-79) demonstrating that Ser(P)75 is also a critical residue for recognition by the antibodies. These data show that the phosphorylated residues in the cluster sequence -Ser(P)66-Ser(P)-Ser(P)68 and in the sequence -Pro73-Asn-Ser(P)-Val-Glu77- are critical for antibody binding to x(s1)-casein(59-79) and further demonstrate that a highly phosphorylated segment of a protein can be antigenic.

Amino Acid Sequence↗
PubMed2006

Resolution and characterisation of multiple isoforms of bovine kappa-casein by 2-DE following a reversible cysteine-tagging enrichment strategy.

Visualisation of multiple isoforms of kappa-casein on 2-D gels is restricted by the abundant alpha- and beta-caseins that not only limit gel loading but also migrate to similar regions as the more acidic kappa-casein isoforms. To overcome this problem, we took advantage of the absence of cysteine residues in alpha(S1)- and beta-casein by devising an affinity enrichment procedure based on reversible biotinylation of cysteine residues. Affinity capture of cysteine-containing proteins on avidin allowed the removal of the vast majority of alpha(S1)- and beta-casein, and on subsequent 2-D gel analysis 16 gel spots were identified as kappa-casein by PMF. Further analysis of the C-terminal tryptic peptide along with structural predictions based on mobility on the 2-D gel allowed us to assign identities to each spot in terms of genetic variant (A or B), phosphorylation status (1, 2 or 3) and glycosylation status (from 0 to 6). Eight isoforms of the A and B variants with the same PTMs were observed. When the casein fraction of milk from a single cow, homozygous for the B variant of kappa-casein, was used as the starting material, 17 isoforms from 13 gel spots were characterised. Analysis of isoforms of low abundance proved challenging due to the low amount of material that could be extracted from the gels as well as the lability of the PTMs during MS analysis. However, we were able to identify a previously unrecognised site, T(166), that could be phosphorylated or glycosylated. Despite many decades of analysis of milk proteins, the reasons for this high level of heterogeneity are still not clear.

Amino Acid Sequence↗
PubMed1993

Human erythrocyte casein kinase II: characterization and phosphorylation of membrane cytoskeletal proteins.

Casein kinase II activities were purified from human erythrocyte membrane and cytosolic fractions to apparent homogeneity. The kinases isolated from the membrane and cytosolic fractions exhibited the same subunit composition and the ability to utilize ATP and GTP as phosphoryl donors. Antibodies against the alpha and alpha' subunits of human casein kinase II cross reacted with the corresponding subunits of both erythrocyte casein kinases. Spermine, spermidine, putrescine, and polylysine stimulated to varying degrees the activities of erythrocyte casein kinase II, whereas heparin inhibited the kinase activities. Both kinases were found to catalyze the phosphorylation of several erythrocyte membrane cytoskeletal proteins, including spectrin, ankyrin, adducin, protein 4.1, and protein 4.9. Unlike casein kinase I, casein kinase II did not phosphorylate band 3 appreciably. A preliminary estimate indicates that both human erythrocyte membrane and cytosolic casein kinase II catalyze the incorporation of approximately 1.2 and 3.5 moles of phosphate into each mole of spectrin and ankyrin, respectively. An analysis of the phosphopeptide maps of ankyrin indicates that both membrane and cytosolic kinases phosphorylate the same domains within ankyrin. These data, taken together, suggest that the type II casein kinases isolated from human erythrocyte membrane and cytosol are either identical or closely related and may play a role in the regulation of cytoskeletal protein interactions.

Adenosine Triphosphate↗
PubMed1996

Correction of dyslipoproteinaemia of casein-fed rabbit by FCE 27677, a potent novel ACAT inhibitor.

Rabbits fed a wheat starch casein diet develop hypercholesterolaemia characterized by the plasma elevation of low density lipoprotein (LDL) that is caused by oversecretion of apoB-100 containing lipoproteins by the liver and by the suppression of the EDTA-sensitive hepatic beta- very low density lipoprotein (VLDL)-LDL receptor. In this study, the effect of FCE 27677 ((-)N-[2,6-bis(1-methylethyl)phenyl]-N'-[(4R,5R)-2-(4-dimethylaminoph eny l)-4,5-dimethyl-dioxolan-2-yl]methylurea) a novel potent systemic acylCoA:cholesterol acetyltransferase (ACAT, EC 2.3.1.26) inhibitor, has been evaluated. When New Zealand White rabbits were fed with casein for 4 weeks, LDL cholesterol increased from 14 +/- 3 mg/dl-1 to 77 +/- 6 mg/dl-1. By contrast the animals receiving FCE 27677 (10 mg kg-1 d-1) mixed with the casein diet maintained a normal LDL concentration (22 +/- 3 mg dl-1). This hypolipidaemic effect was also observed when rabbits previously made hypercholesterolaemic by being fed casein for 4 weeks were then treated for a month with FCE 27677. [125I]LDL plasma turnover studies and [125I]LDL binding studies to liver membranes were carried out with the purpose of investigating the mechanism of action of the drug. The LDL apoB-100 production rate in chow-fed, casein-fed, and casein-fed rabbits receiving FCE 27677, was respectively 10.5, 22.4, and 12.5 mg kg-1 d-1. The turnover rate of [125I]LDL in the animals receiving the drug was not, however, different from that in the rabbits fed the casein diet alone (2.381 vs 2.079 pools d-1). Both values were lower than that in chow-fed animals (3.271 pools d-1). FCE 27677 did not normalize the activity of the hepatic beta-VLDL-LDL EDTA-sensitive receptor which is suppressed by casein feeding. Altogether the results are consistent with the idea that FCE 27677 by acting through inhibition of the cholesterol esterification in the liver normalizes the LDL synthetic rate. ACAT inhibitors may be useful drugs for the treatment of human dyslipoproteinaemia secondary to derangement of the apoB-100 synthetic rate.

Aniline Compounds↗