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Query: UMLS:C0004153 (atherosclerosis)
 77,401 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Aortic smooth muscle cell death is an important initial lesion of atherosclerosis. A number of autooxidation products of cholesterol which has been recognized recently has the capability of inducing rabbits' aortic smooth cell death in vitro. Twelve oxidation derivatives of cholesterol, available commercially, were dissolved in small amounts of ethanol, then added to the culture medium at levels not exceeding 0.8%. The medium contained 10% fetal calf's serum which served as an in situ vehicle for the sterols. The degrees of cytotoxicity were graded and measured as percentage of dying and dead cells in the cultures within 24 hr. 25-Hydroxycholesterol and cholesthan-3 beta, 5 alpha, 6 beta-triol, were the most toxic compounds among the sterols tested. When these oxidation derivatives of cholesterol were added to these cultured cells, they significantly depressed activity of 3-hydroxy-3-methylglutaryl coenzyme A reductase, a regulatory enzyme of cholesterol biosynthesis (up to 83% inhibition by 25 hydroxycholesterol at a 3 microgram/ml concentration in culture medium) but the sequence of degree of inhibition was not exactly correlated with that of cytotoxicity. Various mechanisms are speculated. Purified cholesterol showed no cytotoxic effect and minimal inhibition of cholesterol biosynthesis.
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PMID:Cytotoxicity of oxidation derivatives of cholesterol on cultured aortic smooth muscle cells and their effect on cholesterol biosynthesis. 3 98

A simple procedure has been devised to give virtually pure preparations of polymorphonuclear leucocytes. This has permitted study of the regulation of cholesterol biosynthesis at cell level. Freshly isolated cells from donors with various forms of hyperlipoproteinaemia have been shown to have very low levels of cholesterol synthesis, presumably due to high circulating levels of apoprotein-B in donor plasma [1]. The activity of the rate-limiting enzyme for cholesterol biosynthesis, 3-hydroxy-3-methylglutaryl coenzyme A reductase, rapidly increases as the cells are incubated in lipoprotein-deficient medium, until, by 12 h, cells from patients heterozygous for familial type IIa hypercholesterolaemia are clearly distinguished from other hyperlipoproteinaemias. The possible significance of this finding is discussed in relation to the causation and treatment of atherosclerotic disease.
Atherosclerosis 1978 Mar
PMID:Regulation of cholesterol synthesis in the hyperlipoproteinaemias. Polymorphonuclear leucocyte abnormality specific to familial type II hypercholesterolaemia. 20 84

Sterol synthesis from radioactive acetate and the suppression of this synthesis by human low density lipoprotein (LDL) have been investigated in skin fibroblast strains derived from infant donors and from donors over the age of 70 years. The activity of the enzyme hydroxymethylglutaryl-CoA reductase and its repression by LDL has also been investigated in these fibroblast strains and in senescent cells of the foetal lung cell strain MRC-5. No age-related differences could be detected either in repression of [3H]acetate incorporation by LDL, or in repression of HMG-CoA reductase activity.
Atherosclerosis 1979 Jul
PMID:Regulation of cholesterol synthesis in skin fibroblasts derived from old people. 22 8

The nephrotic syndrome is often accompanied by hyperlipidemia associated with an increased risk of accelerated atherosclerosis. The present study was undertaken to evaluate the effects of pravastatin, a novel competitive inhibitor of 3-hydroxy-3-methylglutaryl coenzyme A reductase, on the serum lipids and apolipoproteins in patients with this syndrome and marked hyperlipidemia. Eleven adult patients received 10 mg of pravastatin twice daily for 4 to 8 weeks. The total serum cholesterol decreased from 426 +/- 44 to 309 +/- 18 mg/dl (-27.4%, mean +/- S.E.; p less than 0.01) following administration of pravastatin. The serum triglyceride decreased from 332 +/- 122 to 229 +/- 50 mg/dl (-30.9%), although this change was not significant. Despite the fact that the HDL cholesterol level was barely changed (51 +/- 7 to 51 +/- 6 mg/dl), the LDL cholesterol fell from 313 +/- 30 to 211 +/- 16 mg/dl (-32.5%; p less than 0.005), and the LDL to HDL cholesterol ratio fell from 7.57 +/- 1.59 to 4.94 +/- 0.88 (-34.8%; p less than 0.05). These changes caused the atherogenic index to decline from 9.6 +/- 2.4 to 6.1 +/- 1.2 (-36.5%; p less than 0.05). No significant alterations could be found among apolipoproteins A-1, A-2, B, C-2, C-3, and E. During the present study period, pravastatin was well tolerated and did not affect the serum protein, albumin, serum urea nitrogen, creatinine levels, or urine protein excretion. Also, there were no serious adverse effects. Pravastatin appears to be effective for treating patients with hyperlipidemia of the nephrotic syndrome.
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PMID:Effects of pravastatin on serum lipids and apolipoproteins in hyperlipidemia of the nephrotic syndrome. 163 84

Using differential hybridization techniques we have isolated a hamster cDNA encoding a cholesterol-regulated protein. By sequence homology we concluded that the isolated cDNA encodes alpha 1-inhibitor III (alpha 1 I3), a protein of the alpha-macroglobulin (alpha M) family. When hamsters were fed diets rich in cholesterol, cholic acid, or chenodeoxycholic acid, the amount of alpha 1I3 RNA was reduced between 5- and 10-fold. Drugs that lower plasma cholesterol levels, such as colestipol and mevinolin, increased alpha 1I3 RNA between 2- and 3-fold. Additionally, plasma alpha 1I3 protein levels, as measured by immunoblotting techniques using an anti-human alpha 2M antibody, correlate well with alpha 1I3 RNA levels in those hamsters. Plasma alpha 1I3 protein was inversely proportional to plasma cholesterol levels in those hamsters. The observed suppression of alpha 1I3 expression by cholesterol mimics the cholesterol-mediated regulation of other genes that maintain cholesterol homeostasis, such as 3-hydroxy-3-methylglutaryl coenzyme A synthase, 3-hydroxy-3-methylglutaryl coenzyme A reductase, and low density lipoprotein receptor. We hypothesize that alpha 1I3 may play a role in the onset of atherosclerosis and may provide a link between cholesterol and the clotting system. Furthermore, the availability of another sterol-regulated gene, like alpha 1I3, should help elucidate the molecular mechanisms of cholesterol-mediated regulation of gene transcription.
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PMID:Cholesterol-mediated suppression of alpha 1-inhibitor III, a plasma alpha-macroglobulin family protein. 171 65

The 3-years efficacy and safety of the 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitor simvastatin (S) (previously called synvinolin or MK-733) has been studied in single and combined therapy with cholestyramine (C) in 48 hypercholesterolaemic patients. Plasma lipids, lipoproteins and apolipoproteins A-I and B, and blood safety tests (haematology, liver function, creatine phosphokinase (CPK), creatinine, blood glucose and thyroid function) were determined regularly throughout the study. Extensive ophthalmological examinations with particular focus on the lens were done before initiation of therapy and at every 6 months during drug treatment. Maximal reductions of mean plasma total cholesterol concentration (34% with S; 47% with S + C) and low-density lipoprotein (LDL)-cholesterol concentration (42% with S; 56% with S + C) were achieved after 4 weeks on full-dose therapy. During continued treatment, years 1 through 3, the reduction of mean plasma total cholesterol was 26-29% with S alone, and 31-41% with S + C. Significant reductions of plasma triglycerides (15-27%) and very low density lipoprotein (VLDL) triglycerides (10-27%) were achieved in the group treated with S as single therapy. In this group there was also a significant increase (10-14%) of high-density lipoprotein (HDL)-cholesterol. In liver aspartate (AST) and alanine (ALT) aminotransferases, as well as alkaline phosphatase (ALP), minor and variable, but usually transient, increases were seen. Repeated ophthalmological examinations did not demonstrate any drug-related side effects. It is concluded that simvastatin is a safe and efficient cholesterol-lowering drug for long-term therapy, both as a single drug and in combination with cholestyramine.
Atherosclerosis 1991 Dec
PMID:Long-term efficacy and safety of simvastatin alone and in combination therapy in treatment of hypercholesterolaemia. 178 13

Normal rabbits typically respond to a diet high in cholesterol with a large increase in the concentration of plasma cholesterol. We have previously described the breeding and partial characterization of a variant rabbit which does not respond to a high cholesterol diet with changes in plasma cholesterol concentration. In the present report we have characterized three components involved in cholesterol homeostasis: the B/E (LDL) receptor, 3-hydroxy-3-methylglutaryl coenzyme A reductase activity (HMG-CoA reductase, EC 1.1.1.34) and acyl-coenzyme A: cholesterol acyltransferase activity (ACAT, EC 2.3.1.26) in the livers of the hypercholesterolemia-resistant rabbits. Using normal cholesterol-fed rabbit [125I] beta-VLDL as a ligand, liver membranes prepared from resistant rabbits fed a low-cholesterol diet had 70% higher binding capacity than membranes from normal rabbits fed the same diet. Similar experiments demonstrated that the resistant rabbits had a 240% higher B/E receptor binding capacity compared to normal animals when liver membranes were prepared from animals fed a 0.25% cholesterol-enriched diet. No difference in the binding affinity of [125I]beta-VLDL was detected in membranes prepared from normal or resistant animals. When fed a low-cholesterol diet, the resistant rabbits had approximately 2-fold higher hepatic HMG-CoA reductase activity (97.4 +/- 3.5 pmol product/mg/min in resistant animals compared to 45 +/- 1.1 pmol product/min/mg in normal animals). The difference was exaggerated in animals fed the 0.25% cholesterol-enriched diet, 73.3 +/- 5.5 vs 2.4 +/- 0.56 pmol product/min/mg for resistant and normal membranes respectively. The basal activity of ACAT in hepatic membranes was significantly lower in the resistant rabbits compared to normal rabbits (138 +/- 11 vs 268 +/- 19 pmol cholesteryl ester/min/mg in resistant and normal rabbits respectively); when fed a 0.25% cholesterol-enriched diet, the enzyme was induced 6-fold in normal animals but was increased only 2-fold in the resistant animal. These biochemical data suggested that the resistant rabbit maintained low intracellular cholesterol even when fed a cholesterol-enriched diet. Direct measurement of cellular cholesterol and cholesteryl esters demonstrated that the concentration of these lipids was significantly lower in the resistant animal than in normal animals with the largest differences found in the cytoplasmic rather than the membrane compartment. These studies demonstrate that the resistant rabbit manifests several quantitative differences in cholesterol metabolism and in the regulation of cholesterol metabolism; but these studies do not directly explain the underlying cause of the resistance to hypercholesterolemia in the resistant rabbit.
Atherosclerosis 1991 Apr
PMID:Cholesterol metabolism in hypercholesterolemia-resistant rabbits. 185 63

NB-598, a new inhibitor of mammalian squalene epoxidase, was found to be a potent inhibitor of microsomal squalene epoxidase from dog liver. Hypolipidemic effects of NB-598 were compared with those of simvastatin (MK-733, a 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitor) in dogs. NB-598 was found to decrease serum total cholesterol levels and increase serum squalene levels in a dose-dependent manner. MK-733 decreased serum total cholesterol and squalene levels. Both NB-598 and MK-733 decreased all classes of lipoprotein cholesterol, and they decreased low density lipoprotein cholesterol most potently. Both drugs decreased phospholipid levels in parallel with cholesterol levels. NB-598 also decreased triacylglycerol levels. After termination of drug administration, these levels returned to the control levels. The potency of NB-598 is thought to be as great or greater than that of MK-733. Moreover, NB-598 increased squalene concentrations in the feces and gallbladder bile, but it did not affect neutral sterol and bile acid concentrations. NB-598 did not affect the lithogenic index.
Atherosclerosis 1991 Jun
PMID:Hypolipidemic effects of NB-598 in dogs. 189 85

Vasomotor reactivity was assessed in vitro in arterial segments obtained from rabbits with different stages of atherosclerosis. Rabbits were fed a standard chow diet (controls) or a cholesterol-enriched diet to induce hypercholesterolemia and atherosclerosis. A third group received the hydroxymethylglutaryl coenzyme A reductase inhibitor, lovastatin, simultaneously with the cholesterol diet. Contractile responses of thoracic aortas to norepinephrine, serotonin, and potassium-rich solution, as well as endothelium-dependent dilations to acetylcholine, were compared after 2 and 4 months on the respective diet. Additionally, plasma cholesterol levels and the amount of plaques covering the intimal surface (as a percentage of the intimal surface) were determined; transmission electron microscopy of atherosclerotic arteries was also performed. After 2 months, the only difference was an enhancement of contractile responses to serotonin in the cholesterol-fed versus the control group. After 4 months on the diet, contractile responses to serotonin were further enhanced, and norepinephrine- and potassium-induced vasoconstrictions were now also significantly enhanced in cholesterol-fed animals versus controls. Endothelium-dependent vasodilations were simultaneously reduced in cholesterol-fed animals. These alterations were partly prevented in cholesterol-fed and lovastatin-treated animals. Suppression of nitric oxide synthesis in control aortas by NG-nitro-L-arginine did not reveal any significant increases in contractile responses. Contractile responses to serotonin were enhanced after 2 months on the diet but before the appearance of intimal plaques, whereas attenuation of endothelium-dependent dilations, as well as the further enhancement of contractile responses to serotonin and to other agonists, were closely correlated with the degree of intimal plaques after 4 months on the diet.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Hypercholesterolemia and atherosclerosis change vascular reactivity in rabbits by different mechanisms. 193 72

There is increasing evidence that conventional lipid-lowering therapy can arrest the progression of coronary atherosclerosis. Trials are now under way to determine whether more radical reduction of low-density-lipoprotein cholesterol will reverse atherosclerosis and lead to regression of coronary lesions. The ability to effect such reductions has been markedly enhanced by the introduction into clinical practice of the 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors.
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PMID:Towards a new era: is coronary artery disease reversible? 207 74


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