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

The association of serum LDL and HDL cholesterol with hepatic microsomal enzyme induction, assessed by plasma antipyrine kinetics was investigated in 30 epileptics. Patients on enzyme-inducing anticonvulsants had reduced LDL/HDL cholesterol ratios and elevated HDL cholesterol concentrations and HDL/total cholesterol ratios, indicating a cholesterol transfer from LDL to HDL. Strong hepatic microsomal enzyme induction was associated with reduced LDL cholesterol. The LDL/HDL cholesterol ratio was negatively proportional and the HDL/total cholesterol ratio positively proportional to the antipyrine clearance rate. Epileptics, particularly those with a high antipyrine clearance, had a cholesterol distribution pattern characteristic of a low probability of developing coronary atherosclerosis. The results support the view that hepatic microsomal enzyme induction favourably alters the cholesterol distribution in the body.
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PMID:Serum LDL cholesterol, the LDL/HDL cholesterol ratio and liver microsomal enzyme induction evaluated by antipyrine kinetics. 666 16

To test the effects of trans unsaturated fatty acids (t-FA) on atherosclerosis, lipidemia and enzyme activities, rabbits were fed a semipurified, cholesterol-free diet containing 40% sucrose, 25% casein and 14% fat for 5 months. Two experimental diets provided either 6% (high) or 3.2% (low) t-FA. The control group was fed a fat of composition similar to the two experimental diets but free of t-FA. Serum cholesterol and triglycerides were elevated in the rabbits fed 6% t-FA. Liver glycerides were also elevated in this group. The fatty acids of plasma, erythrocytes, epididymal fat, liver microsomes and liver mitochondria reflected the dietary composition. Levels of aortic atherosclerosis were identical in the three groups. There were no significant differences in activity of five hepatic enzymes: glucose-6-phosphatase (microsomal), fatty acid synthetase (cytosolic), malate dehydrogenase, beta-hydroxybutyrate dehydrogenase and monoamine oxidase (mitochondrial).
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PMID:Influence of trans unsaturated fats on experimental atherosclerosis in rabbits. 683 52

When cultured human skin fibroblasts were incubated at 37 degrees C with sonically dispersed positively charged sphingomyelin liposomes, sphingomyelin accumulated within the cell. This resulted in stimulation of cholesterol synthesis by increasing 3-hydroxy-3-methylglutaryl Coenzyme A reductase activity. Activation was rapid and was not due to the efflux of cell cholesterol or to cell growth and proliferation. Neither low density lipoprotein cholesterol nor nonlipoprotein cholesterol could suppress the sphingomyelin-induced cholesterol synthesis or activate the acyl-CoA cholesterol acyltransferase, despite an increase in cell cholesterol content. In contrast, the response to 7-ketocholesterol or 26-hydroxycholesterol was not impaired. The effect of sphingomyelin on cholesterol synthesis was temporary and reversible. Twenty-four hours after removal of sphingomyelin, cholesterol synthesis returned to normal and could be suppressed by LDL. Accumulation of sphingomyelin in the cell decreased lysosomal cholesteryl ester hydrolase but had no effect on the microsomal cholesteryl ester hydrolase. These results suggest that accumulation of sphingomyelin in the cell markedly affects cellular cholesterol homeostasis. Resultant accumulation of cholesteryl esters in the presence of extracellular cholesterol could be relevant to atherogenesis.
Atherosclerosis 1983 Mar
PMID:Effect of positively charged sphingomyelin liposomes on cholesterol metabolism of cells in culture. 684 46

Arteriosclerotic lesions were formed in rat aorta by the administration of vitamin D2, a high-fat diet and a thyroid suppressing agent. This treatment increased the serum total cholesterol level to 12 times the control level. In the arteriosclerotic lesions that were induced the activities of lysosomal enzymes, such as acid phosphatase and acid lipase, were higher than in controls, that of acid cholesterol esterase was decreased, those of microsomal lipid-synthesizing enzymes--such as acyl-CoA synthetase and cholesterol ester synthesizing activity--were increased and that of neutral cholesterol esterase was decreased. These data suggest that lipid metabolism in arteriosclerotic lesions was changed, resulting in the accumulation of cholesterol esters in the aorta. Administration of high-fat diet and thyroid suppressing agent also increased the serum cholesterol levels to 12-fold the control level, but did not induce arteriosclerotic lesions. After this treatment the activities of hydrolyzing enzymes, such as acid and neutral cholesterol esterase and lipase, in the aorta increased, but the activities of lipid synthesizing enzymes also increased. These data suggest that lipid metabolism in the aorta in this condition changed to compensate for the large influx of serum lipids and to prevent arteriosclerosis. The roles of the serum lipid level, cell injury and lipid metabolism in the aorta in forming arteriosclerotic lesions are discussed on the basis of these results.
Atherosclerosis 1982 May
PMID:Lipid metabolism in arteriosclerotic arterial wall of rats. 709 82

Bezafibrate markedly reduced the activity of fatty acyl CoA:cholesterol acyltransferase (ACAT) in the microsomal fraction of aortas from cholesterol-fed rabbits, while clofibrate was a less potent inhibitor. The activity of lysosomal cholesterol ester hydrolase (LCEH) was not significantly affected by either agent, indicating that inhibition of ACAT rather than stimulation of LCEH is a mechanism whereby these agents may decrease the cholesterol ester content of atherosclerotic aorta.
Atherosclerosis 1982 Oct
PMID:The effect of bezafibrate and clofibrate on microsomal ACAT and lysosomal cholesterol ester hydrolase activity in the cholesterol-fed rabbit aorta. 715 86

Accumulation of cholesteryl esters in arterial tissue is a prominent feature of human and experimental atherosclerosis. This accumulation does not occur in undisturbed venous tissue, but has been reported in veins which have been surgically placed into the arterial system as bypass grafts. The formation of cholesteryl esters and some properties of the fatty acyl-CoA:cholesterol acyltransferase system have been studied in microsomal preparations from canine arterial and venous tissue. The rate of synthesis of cholesteryl palmitate was five-fold faster in venous than in arterial preparations. There was no difference, however, in the apparent Km values. Our results indicate that venous tissue possesses active fatty acyl-CoA:cholesterol acyltransferase activity which may be partly responsible for the accumulation of cholesteryl esters in veins grafted into the arterial system.
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PMID:Cholesteryl ester synthesis in canine vein and artery. 731 78

When experimental animals are kept on an atherogenic diet the NADP.H-dependent phospholipid deoxygenase in the membranes of the hepatic endoplasmic reticulum is activated and the degree of membrane oxidation is increased. "Peroxide" modification of microsomal membranes is attended by changes in their conformation and as a consequence, changes in the activity of membrane-bound enzymes. Proceeding from the fact that the synthesis of the components and the assembly of the supramolecular lipoprotein structure as well as cholesterol catabolism are accomplished by the enzyme systems localized in the hepatic microsomes, the role of peroxidation of the microsomal lipids in the pathogenesis of atherosclerosis is discussed.
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PMID:[Lipid peroxides and atherosclerosis. Hypothesis: the role of cholesterol and free-radical lipid peroxidation in altering cell membrane properties in hypercholesterolemia and atherosclerosis]. 741 95

The local anesthetics lidocaine, tetracaine, benzocaine and dibucaine were found to inhibit sterol esterification by acylCoA:cholesterol acyltransferase (ACAT, EC 2.3.1.26) in the microsomal fraction isolated from rabbit aortas. In arterial microsomes, the incorporation of [14C]oleoylCoA into [14C]steryl esters was inhibited in a dose-dependent way by the anesthetics over the concentration range 0.25-5.0 mM. The potency of inhibition was dibucaine greater than benzocaine greater than tetracaine greater than lidocaine greater than procaine with inhibition of about 85% occurring with 0.25 mM dibucaine. Sterol esterification to [14C]oleic acid was also inhibited by the anesthetics in intact aortic tissue from the rabbit, dog, and rat. A detailed study of the effects of 5 mM lidocaine on lipid biosynthesis in the rabbit aorta in vitro revealed that lidocaine not only inhibited sterol esterification to [14C]oleate but stimulated [14C]oleate incorporation into glycerides.
Atherosclerosis
PMID:The effect of local anesthetics on arterial lipid metabolism. Inhibition of sterol esterification in vitro. 747 Feb 8

The object of this study was to examine changes in plasma membranes of arterial smooth muscle (ASM) during atherogenesis obtained from cholesterol-fed (2%) rabbits. A microsomal fraction highly enriched with plasma membrane markers was prepared by subcellular organelle fractionation from ASM freshly isolated from the thoracic aorta. The membranes were analyzed for unesterified (free) cholesterol (FC) content, membrane bilayer structural parameters (X-ray diffraction), phospholipid (PL) composition, and Na+/K(+)-ATPase activity and kinetics. Following 8 weeks on diet, membrane FC content increased 67.1%. Small angle X-ray diffraction demonstrated an increase in membrane hydrocarbon core electron density and an increase in overall lipid bilayer width (56-62 A). This increase in bilayer width was highly correlated with the membrane FC content (r = 0.992). Both membrane FC content And bilayer width independently correlated with time on cholesterol diet. The phospholipid profile of the membrane revealed a 16.4% increase in phosphatidylcholine (PC), 19.3% decrease in phosphatidylethanolamine (PE) and 62.8% increase in sphingomyelin (SM) content with no change in total PL content. Na+/K(+)-ATPase activity was decreased 52.2% (P < 0.005), and [3H]ouabain binding kinetics demonstrated a 27.6% decrease in maximum binding sites (Bmax) (P < 0.01) while the dissociation constant (Kd) remained unaltered. Membranes obtained from control ASM cells enriched with FC in culture demonstrated changes similar to those in atherosclerotic ASM membranes including an increase in membrane FC content, an increase in bilayer width, and a decrease in Na+/K(+)-ATPase activity with decreased ouabain Bmax. These data demonstrate marked compositional, structural and functional changes in ASM cell membrane characteristics in dietary atherosclerosis. These changes were highly correlated with cholesterol accumulation in the plasma membrane bilayer and were observed before the appearance of visible lesions. We suggest that these membrane defects may be linked with early atherogenesis.
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PMID:Atherosclerosis alters the composition, structure and function of arterial smooth muscle cell plasma membranes. 754 33

Agents that inhibit hepatic cholesterol biosynthesis reduce circulating cholesterol levels in experimental animals and humans, and may be of pharmacological importance in the prevention of atherosclerosis. Azalanstat (RS-21607), a synthetic imidazole, has been shown to inhibit cholesterol synthesis in HepG2 cells, human fibroblasts, hamster hepatocytes and hamster liver, by inhibiting the cytochrome P450 enzyme lanosterol 14 alpha-demethylase. When administered orally to hamsters fed regular chow, RS-21607 (50 mg/kg/day) lowered serum cholesterol in a dose-dependent manner (ED50 = 62 mg/kg) in a period of 1 week. It preferentially lowered low density lipoprotein (LDL) cholesterol and apo B relative to high density lipoprotein (HDL) cholesterol and apo A-1. It also lowered plasma cholesterol levels in hamsters fed a high saturated fat and cholesterol diet. RS-21607 inhibited hepatic microsomal hydroxymethylglutaryl-CoA (HMG-CoA) reductase activity in hamsters in a dose-dependent manner (ED50 = 31 mg/kg), and this was highly correlated with serum cholesterol lowering (r = 0.97). Cholesterol lowering by azalanstat and cholestyramine was additive, and the increase in HMG-CoA reductase brought about by cholestyramine was attenuated significantly by azalanstat. In vitro studies with HepG2 cells indicated that this modulation of reductase activity was indirect, occurring at a post-transcriptional step, and it is proposed that a regulatory oxysterol derived from dihydrolanosterol (or lanosterol) may be responsible for this regulation. Azalanstat does not appear to lower circulating cholesterol in the hamster by up-regulation of the hepatic LDL receptor, suggesting that other mechanisms are involved. Orally administered azalanstat (50-75 mg/kg) stimulated hepatic microsomal cholesterol 7 alpha-hydroxylase activity by 50-400% in hamsters, and it is postulated that this may result from modified cholesterol absorption and bile acid synthesis.
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PMID:Azalanstat (RS-21607), a lanosterol 14 alpha-demethylase inhibitor with cholesterol-lowering activity. 764 60


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