| For medical practitioners and the general public - Cholesterol Journal Article Catalog. |
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| Influence of cholesterol feeding on bile acid metabolism in young and aged germ-free rats Uchida, K., T. Satoh, et al. (1996), Jpn J Pharmacol 71(2): 113-8. Abstract: The effects of cholesterol feeding on serum and liver cholesterol levels, fecal and biliary bile acid levels, bile acid pool size and bile acid composition were examined in 2-, 12- and 24-month-old male germ-free rats. The major bile acids in these animals were cholic and beta-muricholic acids. Cholesterol feeding increased synthesis of bile acids by 3- to 4-fold, especially that of chenodeoxycholic acid (mainly beta-muricholic acid in the rat), decreasing the cholic acid/chenodeoxycholic acid (CA/CDCA) ratio in all rats regardless of age, even though the CA/CDCA ratio increased as a linear function of age in both diet groups. Cholesterol feeding increased the serum cholesterol level markedly in aged rats. This hypercholesterolemia may be produced by the increase in CA/CDCA ratio in aged rats. |
| Influence of cholesterol on electroporation of bilayer lipid membranes: chronopotentiometric studies Koronkiewicz, S. and S. Kalinowski (2004), Biochim Biophys Acta 1661(2): 196-203. Abstract: This paper presents the results of constant-current (chronopotentiometric) measurements of the egg yolk phosphatidylcholine (PC) bilayer membrane without and with cholesterol. The experiments were performed on planar bilayer lipid membrane (BLM) formed by the Mueller-Rudin method. It is demonstrated that the constant-intensity current flow through bilayer membranes generated fluctuating pores in their structure. The presence of cholesterol in the membrane caused an increase in the value of the breakdown potential. It is postulated that greater stability of the bilayer with cholesterol can result from an increased critical pore radius (at which the bilayer would undergo irreversible rupture). This confirms that cholesterol has a stabilizing effect on BLM. Besides, our results suggest that addition of cholesterol causes shift in the distribution of pore conductance towards a smaller value. It is suggested that this can be connected with the phenomenon of domain formation in the membranes containing high concentration of cholesterol. Moreover, it is shown that chronopotentiometry with programmable current intensity is a promising method for observation of the membrane recovery process. |
| Influence of cholesterol on liposome fluidity by EPR. Relationship with percutaneous absorption Coderch, L., J. Fonollosa, et al. (2000), J Control Release 68(1): 85-95. Abstract: The influence of liposome composition on bilayer fluidity and its effect on the percutaneous absorption into the skin were investigated. Liposomes formed with saturated or unsaturated phospholipids (H-PC or PC) with varying amounts of cholesterol were prepared and their penetration behaviour into the stratum corneum was followed up by means of the stripping method. The order and dynamics of the hydrophobic domain of the vesicles were studied using electron paramagnetic resonance (EPR) methodology. Phospholipid composition and the amount of cholesterol exert a considerable influence on the penetration behaviour of the probe encapsulated in the liposomes. This behaviour is closely related to the fluidity characteristics of these liposomes studied by EPR. Therefore, a penetration mechanism of the vesicles into the skin, based on the incorporation of lipids into the skin lipids and on fluidity behaviour, is suggested. |
| Influence of cholesterol on phospholipid bilayers phase domains as detected by Laurdan fluorescence Parasassi, T., M. Di Stefano, et al. (1994), Biophys J 66(1): 120-32. Abstract: Coexisting gel and liquid-crystalline phospholipid phase domains can be observed in synthetic phospholipid vesicles during the transition from one phase to the other and, in vesicles of mixed phospholipids, at intermediate temperatures between the transitions of the different phospholipids. The presence of cholesterol perturbs the dynamic properties of both phases to such an extent as to prevent the detection of coexisting phases. 6-Lauroyl-2-dimethylaminopahthalene (Laurdan) fluorescence offers the unique advantage of well resolvable spectral parameters in the two phospholipid phases that can be used for the detection and quantitation of coexisting gel and liquid-crystalline domains. From Laurdan fluorescence excitation and emission spectra, the generalized polarization spectra and values were calculated. By the generalized polarization phospholipid phase domain coexistence can be detected, and each phase can be quantitated. In the same phospholipid vesicles where without cholesterol domain coexistence can be detected, above 15 mol% and, remarkably, at physiological cholesterol concentrations, > or = 30 mol%, no separate Laurdan fluorescence signals characteristic of distinct domains can be observed. Consequences of our results on the possible size and dynamics of phospholipid phase domains and their biological relevance are discussed. |
| Influence of cholesterol on sphingomyelin metabolism and hemileaflet fluidity of rat liver plasma membranes Nikolova-Karakashian, M. N., H. Petkova, et al. (1992), Biochimie 74(2): 153-9. Abstract: The objective of this study was to examine the effect of dietary Chol supplementation on SM metabolism in rat liver plasma membranes, as well as on membrane leaflet fluidity characteristics. The membrane Chol content increased significantly during the first 20 days of dietary feeding, but returned to the level of the control group when the diet was continued for another ten days. The initially more fluid outer leaflet of the membrane rigidified as a result of the diet, obliterating the natural asymmetry in the fluidity of the membrane bilayer. Changes in the neutral SMase activity were also observed. These changes were in strong negative correlation (r = -0.978) with the Chol/Pr ratio and are consistent with the in vitro inhibition of SMase activity reported earlier. In contrast, the SM synthesizing enzymes, PC:Cer-PCh and PE:Cer-PEt transferase, were stimulated in course of the dietary Chol feeding. The activity of PC:Cer-PCh transferase was more strongly affected. Our results support the concept that SM metabolism is regulated coordinately with that of Chol. The present work could contribute to the better understanding of the parallel accumulation of SM and Chol observed in a variety of pathological conditions such as atherosclerosis and Niemann-Pick disease. |
| Influence of cholesterol on survival after stroke. Beneficial effects of cholesterol lowering on atherosclerosis may not lessen with age Stoy, N. (1997), Bmj 315(7116): 1158; author reply 1159. |
| Influence of cholesterol on survival after stroke. Cholesterol may be marker of inflammation Socin, H. V. (1997), Bmj 315(7116): 1159. |
| Influence of cholesterol on survival after stroke. Effect of cholesterol on prognosis may rely on negative association with atrial fibrillation Marini, C., M. Di Napoli, et al. (1997), Bmj 315(7116): 1159. |
| Influence of cholesterol on survival after stroke. Regression to the mean may have been a factor Hutchesson, A. and S. Martin (1997), Bmj 315(7116): 1158; author reply 1159. |
| Influence of cholesterol on survival after stroke: retrospective study Dyker, A. G., C. J. Weir, et al. (1997), Bmj 314(7094): 1584-8. Abstract: OBJECTIVE: To investigate the association between serum cholesterol concentration and cerebrovascular disease. DESIGN: Retrospective study. SETTING: Acute stroke unit of inner city general hospital. SUBJECTS: 977 patients with acute stroke. MAIN OUTCOME MEASURES: Serum total cholesterol concentration, type of stroke investigated by computed tomography or magnetic resonance imaging, three month outcome (good (alive at home) or bad (dead or in care)), long term mortality. RESULTS: After adjustment for known prognostic factors, higher serum cholesterol concentrations were associated with reduced long term mortality after stroke (relative hazard 0.91 (95% confidence interval 0.84 to 0.98) per mmol/l increase in cholesterol) independently of stroke type, vascular territory and extent, age, and hyperglycaemia. Three month outcome was also influenced independently by serum cholesterol (P = 0.024). CONCLUSIONS: Our data suggest an association between poor stroke outcome and lower serum cholesterol concentration. Until a prospective controlled study has confirmed the benefits of lowering cholesterol concentration in elderly subjects, the application of cholesterol lowering guidelines cannot be justified as secondary prevention of acute stroke. |
| Influence of cholesterol on the association of plasma proteins with liposomes Semple, S. C., A. Chonn, et al. (1996), Biochemistry 35(8): 2521-5. Abstract: The in vivo association of blood proteins with large unilamellar liposomes composed of saturated phosphatidylcholines was analyzed to determine the effect of membrane fluidity and hydrocarbon chain length on liposome-plasma protein interactions and liposome clearance. Liposomes composed of dimyristoylphosphatidylcholine (DMPC), dipalmitoylphosphatidylcholine (DPPC), distearoylphosphatidylcholine (DSPC), and diarachidoylphosphatidylcholine (DAPC) were administered via the lateral tail vein of CD-1 mice and were subsequently isolated from the blood at 2 min postinjection. The protein binding ability (PB, grams of protein bound per mole total lipid) of the liposomes was quantified and related to their circulation half-lives. Liposomes composed of long-chain saturated phospholipids that exist in the gel (frozen) state at 39 degrees C (DPPC,DSPC and DAPC) bound large quantities of blood proteins, in excess of 48 g of protein per mole total lipid, and were found to be rapidly cleared from the circulation. The incorporation of cholesterol into DSPC liposomes resulted in significantly decreased PB values and enhanced circulation lifetimes for this lipid system. This cholesterol effect plateaued at 30 mol % cholesterol, corresponding to the loss of the gel-liquid crystalline phase transition, and resulted in PB values of 23-28 grams of protein per mole of total lipid. The types of blood proteins binding to DSPC liposomes were not significantly altered by the inclusion of cholesterol. This is the first demonstration of rapid clearance of neutral large unilamellar liposomes having high levels of bound protein. |
| Influence of cholesterol on the biophysical properties of the sphingomyelin/DOPC binary system Hao, Y. H. and J. W. Chen (2001), J Membr Biol 183(2): 85-92. Abstract: The influence of cholesterol on the sphingomyelin (SM)/dioleoylphosphatidylcholine (DOPC) binary system was investigated in various respects. Electron spin resonance (ESR) measurements reveal that the order parameter of 5DS (5-doxyl stearic acid) in SM/DOPC bilayers increases notably when the concentration of cholesterol is over 30 mol%. Membrane potential measurements indicate that the K+ permeability of the SM/DOPC bilayer decreases steeply at 40 mol% cholesterol concentration. Both these experiments suggest that cholesterol reduces the motion amplitude of hydrocarbon chains abruptly above 30 mol%. In contrast to the ordering effects on the hydrocarbon chains, (31)P-NMR results indicate that cholesterol slightly increases the motion of phosphate groups of the lipids. (31)P-NMR also raises the possibility of domain formation in the presence of cholesterol. Fluorescence-quenching experiments verified that solid domains appear in the binary system when cholesterol is present, and percolation threshold occurs at 50 mol% cholesterol concentration. The solid domains bear the properties of liquid ordered phase, which is the basic structure of caveolae and functional rafts. So this work provides an artificial model for the study of rafts and caveolae on biological membranes. |
| Influence of cholesterol on the interaction of alpha-crystallin with phospholipids Tang, D., D. Borchman, et al. (1998), Exp Eye Res 66(5): 559-67. Abstract: The influence of cholesterol on the binding of alpha-crystallin to pure phospholipid membranes was studied. The rationale of this investigation stems from two unique aspects of human lens cells: an unusually high level of cholesterol in the membranes and the specific binding of alpha-crystallin to membranes. In the absence of cholesterol, binding of alpha-crystallin liposomes composed of either sphingomyelin, disteroyl-phosphatidylcholine or egg-phosphatidylcholine caused a decrease in the fluorescence intensity and anisotropy of the fluorophore NBD-PE. Since this fluorescence probe resides in the polar headgroup region of the membrane, the observed changes indicated that the binding of alpha-crystallin affected the structure of these membrane regions. The ability of alpha-crystallin to modulate membrane structure suggests yet another potential role for this lens protein. Addition of cholesterol markedly decreased the binding of alpha-crystallin to liposomes composed of either sphingomyelin or disteroylphosphatidylcholine and antagonized the capacity of bound alpha-crystallin to decrease membrane surface order. This antagonism could be explained by the ability of cholesterol to directly decrease the anisotropy of the fluorophore in sphingomyelin membranes unexposed to alpha-crystallin. Thus, with cholesterol present, a further decrease in membrane order upon subsequent binding of alpha-crystallin was less likely. The results obtained with the sphingomyelin liposomes are considered most meaningful, since sphingomyelins are the principal phospholipids in the human lens nuclear membrane and cholesterol preferentially interacts with sphingomyelin. We conclude that cholesterol in lipid membranes can antagonize the binding of alpha-crystallin and thus interfere with the capacity of bound alpha-crystallin to alter membrane order. We suggest that such actions of cholesterol might serve to preserve lens membrane structure in the physiological state where the concentration of soluble alpha-crystallin is great. |
| Influence of cholesterol oxides on endocytosis of cultured endothelial and smooth muscle cells Peng, S. K., B. Hu, et al. (1990), Artery 17(2): 84-95. Abstract: Human umbilical vein endothelial cells and rabbit aortic smooth muscle cells in culture were incubated for intervals up to 24 hrs with varying concentrations of cholesterol, 7-ketocholesterol, 25-hydroxycholesterol, cholestane-3 beta,5 alpha,6 beta-triol or cholesterol-5 alpha, 6 beta-epoxide. Endocytosis, as measured by uptake of horseradish peroxidase (HRP), was inhibited in a dose and time dependent manner in both endothelial and smooth muscle cell cultures by cholestane-3 beta,5 alpha,6 beta-triol and 25-hydroxycholesterol. Inhibition by 7-ketocholesterol in endothelial cells occurred only at higher concentrations, and cholesterol and cholesterol epoxide showed no significant inhibitory effects. The viability of the cells exposed to the cholesterol oxides at the concentrations that inhibited the uptake of HRP was not changed. Cholesterol oxides induce functional endothelial injury, not morphologically apparent, which may be involved in atherogenesis. |
| Influence of cholesterol screening and nutritional counseling in reducing cholesterol levels in children. The American Heart Association Fitch, J., R. E. Garcia, et al. (1997), Clin Pediatr (Phila) 36(5): 267-72. Abstract: The purpose of this study was to determine whether cholesterol screening and nutritional counseling can reduce cholesterol concentrations in populations of otherwise unrecognized hypercholesterolemic children. A large pediatric practice in Parma Heights, Ohio, has conducted cholesterol surveillance of children over 2 years of age since 1986. The importance of cholesterol and other recognized risk factors for the progression of atherosclerosis is discussed with all families, and the American Heart Association's Step-One diet is recommended. The present study examines data from a cohort of 894 children (473 boys, 421 girls) who had cholesterol concentrations above 185 mg/dL (4.79 mmol/L) (the 90th percentile) at baseline and, after counseling, had a repeat measurement an average of 2.2 years later. Their mean ages were 7 years at the first testing and 9.2 years at the second. Children who had cholesterol concentrations above 200 mg/dL (5.18 mmol/L) (the 95th percentile) had lipoprotein profiles done, and if their LDL cholesterol exceeded 130 mg/dL (3.37 mmol/L) (the 95th percentile), they were referred to a nutritionist, and family members were advised to have their blood lipids analyzed. Mean cholesterol concentration for all 894 children over this time period decreased by 9.4% (19.5 mg/dL 0.51 mmol/L; 95% CI = 17.5 mg/dL 0.45 mmol/L to 21.5 mg/dL 0.56 mmol/L; P < 0.001). A similar decrease of 8.6% (16.6 mg/dL 0.43 mmol/L); 95% CI = 14.0 mg/dL 0.36 mmol/L to 19.3 mg/dL 0.50 mmol/L); P < 0.001) was observed for the 463 children who had initial cholesterol concentrations between 185 and 200 mg/dL (4.79 and 5.18 mmol/L) and who therefore received a less intense intervention. Cholesterol concentrations in groups of otherwise unidentified hypercholesterolemic children can be significantly reduced as a result of cholesterol screening and nutritional counseling in a pediatric practice setting. |
| Influence of cholesterol status on blood lipid and lipoprotein enzyme responses to aerobic exercise Grandjean, P. W., S. F. Crouse, et al. (2000), J Appl Physiol 89(2): 472-80. Abstract: To compare postexercise changes in plasma lipids and lipoprotein enzymes in 13 hypercholesterolemic (HC) and 12 normocholesterolemic men total cholesterol (TC) 252 +/- 5 vs. 179 +/- 5 mg/dl, fasting blood samples were obtained 24 h before, immediately, 24, and 48 h after a single bout of treadmill walking (70% peak O(2) consumption, 500 kcal expenditure). Significant findings (P < 0.05 for all) for plasma volume-adjusted lipid and enzyme variables were that TC, low-density-lipoprotein cholesterol, and cholesterol ester transfer protein activity were higher in the HC group but did not influence the lipid responses to exercise. Across groups, TC was transiently reduced immediately after exercise but returned to baseline levels by 24 h postexercise. Decreases in triglyceride and increases in high-density-lipoprotein cholesterol (HDL-C) and HDL(3)-C were observed 24 h after exercise and lasted through 48 h. Lipoprotein lipase activity was elevated by 24 h and remained elevated 48 h after exercise. HDL(2)-C, cholesterol ester transfer protein activity, hepatic triglyceride lipase, and lecithin: cholesterol acyltransferase activities did not change after exercise. These data indicate that the exercise-induced changes in HDL-C and triglyceride are similar in HC and normocholesterolemic men and may be mediated, at least in part, by an increase in lipoprotein lipase activity. |
| Influence of cholesterol supply on cell growth and differentiation in cultured enterocytes (CaCo-2) Herold, G., R. Jungwirth, et al. (1995), Digestion 56(1): 57-66. Abstract: When used as treatment for hypercholesterolemia HMG-CoA reductase inhibitors will first pass through and act upon the gut mucosa. Although cholesterol availability is essential for cell growth of the intestinal mucosa adverse intestinal events are rare which is possibly due to hitherto undefined compensatory mechanisms. In the present work we therefore studied the long-term influence of mevinolin on proliferation and differentiation of CaCo-2 cells as an enterocyte model and their response upon the cholesterol supply of different origin. Mevinolin caused a marked and dose-dependent inhibition of cell proliferation, microvilli length and alkaline phosphatase. This parallel suppression was reversed by the addition of either exogenous free cholesterol, endogenous cholesterol from mevalonolactone or LDL but not HDL3. Surprisingly, sucrase activity reacted in an inverse fashion to alkaline phosphatase activity. Mevinolin induced enzyme activity and this was further enhanced by mevalonolactone supply, while cholesterol and LDL normalized sucrase to controls. In conclusion, the presence of luminal cholesterol as well as plasma LDL as the cholesterol source for the enterocyte may prevent mevinolin toxicity. |
| Influence of cholesterol, triglycerides and fibrinogen on AT III, PC, HC-II and plasminogen measurement Tosetto, A., E. Gatto, et al. (1997), Thromb Haemost 77(4): 804. |
| Influence of cholesterol-lowering on plasma membrane lipids and function Lijnen, P., D. Echevaria-Vazquez, et al. (1996), Methods Find Exp Clin Pharmacol 18(2): 123-36. Abstract: In order to determine whether alterations in membrane or plasma lipids affect transmembrane cationic transport systems in erythrocytes and platelets, cationic fluxes and intracellular concentrations, membrane lipids, plasma lipids, lipoproteins and apolipoproteins were measured in hypercholesterolemic patients before and during administration of a HMG-CoA reductase inhibitor. After a 1-month placebo run-in period, the patients were treated double-blind either with placebo (n = 25) or with pravastatin (n = 25) for 6 months. Placebo or pravastatin 10 mg during the 1st month, 20 mg during the 2nd month and 40 mg during the additional 4 months was administered once daily in the evening. Blood was collected in the morning after an overnight fast for assay of membrane and plasma lipids and of cationic fluxes and concentrations, at the end of the placebo run-in period and after 1, 2, 3 and 6 months of pravastatin therapy. Compared to the placebo group the plasma concentration of total cholesterol and phospholipids, free cholesterol and cholesterol esters, and plasma LDL-cholesterol and LDL-phospholipids were decreased during 6 months of pravastatin therapy. No changes in plasma VLDL-, HDL-, HDL2- or HDL3-cholesterol, phospholipids or triglycerides were observed in the pravastatin-treated patients. A decrease in the plasma level of apolipoprotein B and of LDL-apo B, but not of VLDL-apo B, was observed during pravastatin therapy; the plasma apolipoprotein AI and AII levels, as well as HDL2- and HDL3-apo AI and apo AII levels, however, remained unchanged. Plasma lipoprotein Lp(a) did not change during pravastatin therapy, while the plasma lecithin cholesterol acyltransferase activity (LCAT) increased. Compared to the placebo group the erythrocyte and platelet membrane cholesterol content was reduced in the pravastatin-treated patients. The intraerythrocyte and intraplatelet Na+ concentration was reduced during pravastatin administration, while the erythrocyte and platelet Na+/K+ pump activity was increased. However, the intraerythrocyte and intraplatelet K+, Mg2+, cytosolic Ca2+ concentration and water content as well as the erythrocyte Na+/Li+ countertransport and Na+/K+ cotransport activity and the Na+ and K+ leak were not changed during pravastatin treatment. Our data show that cholesterol lowering in hypercholesterolemic patients may result in a significant decrease in erythrocyte and platelet membrane cholesterol content. These changes in plasma membrane cholesterol are accompanied by an increase in the Na+ pump activity and a decrease in intracellular Na+ concentration. Whether these changes in membrane lipids and function observed during cholesterol lowering also occur in other cells remains to be further elucidated. |
| Influence of curcumin on cyclosporin-induced reduction of biliary bilirubin and cholesterol excretion and on biliary excretion of cyclosporin and its metabolites Deters, M., C. Siegers, et al. (2000), Planta Med 66(5): 429-34. Abstract: We investigated the ability of curcumin, which can be extracted from different Curcuma species, to prevent cyclosporin-induced reduction of biliary bilirubin and cholesterol excretion, and its influence on biliary excretion of cyclosporin (CS) and its metabolites in the bile fistula model in rats. I.v. injection of curcumin (25 and 50 mg/kg) after 30 min increased dose-dependently basal bile flow (30 microliters/kg/min) up to 200%, biliary bilirubin excretion (3000 pmol/kg/min) up to 150%, and biliary cholesterol excretion (22 nmol/kg/min) up to 113%. CS (30 mg/kg) reduced bile flow to 66% and biliary excretion of bilirubin and of cholesterol to 33% of the basal value 30 min after i.v. injection. I.v. administration of curcumin (25 and 50 mg/kg) 30 min after CS increased bile flow dose dependently again to 130% for 1 hour and biliary excretion of cholesterol and of bilirubin to 100% of the basal value for 30 and 150 min, respectively. Injection of curcumin 15 min before CS prevented the CS-induced drop of bile flow at 50 mg/kg and reduction of biliary bilirubin excretion already at 25 mg/kg until the end of the experiment (180 min). The CS-induced reduction of biliary cholesterol excretion, however, was not prevented by curcumin. Finally, the biliary excretions of CS (1200 ng/kg/min) and its metabolites (1200 ng/kg/min) were slightly reduced by curcumin at a dose of 50 mg/kg (to 83% of the initial values). The clinical importance of these controversial effects remains to be shown. |