Cholesterol Journal Articles

Record 7221 to 7240

Improving the reliability of total and high-density lipoprotein cholesterol measurements. Four testing strategies compared in a high-risk population
Christenson, R. H., J. R. Roeback, Jr., et al. (1991), Arch Pathol Lab Med 115(12): 1212-6.
Abstract: Four testing strategies for assessing total and high-density lipoprotein cholesterol are compared in a homogeneous group of male outpatients at increased risk for cardiovascular disease: (1) a single measurement at one occasion; (2) the mean of duplicate measurements at one occasion; (3) the mean of single measurements in specimens collected 1 week apart; and (4) the overall mean of duplicate measurements at two occasions 1 week apart. Results of strategy 1 were comparatively less reliable as demonstrated by lower intraclass correlation coefficients and higher within-subject variance components. Use of strategy 3 decreased within-subject variance by 50% and improved the 95% confidence interval by 30% for both total and high-density lipoprotein cholesterol, compared with strategy 1. Duplicate testing on either one or two occasions resulted in a nominal improvement in reliability and confidence. Calculating the mean of single measurements in specimens collected 1 week apart is clinically useful because: (1) it reduces the risk of misclassification, (2) it improves intervention monitoring, (3) it supports the National Cholesterol Education Program guidelines for total cholesterol, and (4) it improves the use of high-density lipoprotein as an independent risk factor.

Imputations of missing values in practice: results from imputations of serum cholesterol in 28 cohort studies
Barzi, F. and M. Woodward (2004), Am J Epidemiol 160(1): 34-45.
Abstract: Missing values, common in epidemiologic studies, are a major issue in obtaining valid estimates. Simulation studies have suggested that multiple imputation is an attractive method for imputing missing values, but it is relatively complex and requires specialized software. For each of 28 studies in the Asia Pacific Cohort Studies Collaboration, a comparison of eight imputation procedures (unconditional and conditional mean, multiple hot deck, expectation maximization, and four different approaches to multiple imputation) and the naive, complete participant analysis are presented in this paper. Criteria used for comparison were the mean and standard deviation of total cholesterol and the estimated coronary mortality hazard ratio for a one-unit increase in cholesterol. Further sensitivity analyses allowed for systematic over- or underestimation of cholesterol. For 22 studies for which less than 10% of the values for cholesterol were missing, and for the pooled Asia Pacific Cohort Studies Collaboration, all methods gave similar results. For studies with roughly 10-60% missing values, clear differences existed between the methods, in which case past research suggests that multiple imputation is the method of choice. For two studies with over 60% missing values, no imputation method seemed to be satisfactory.

In a quasi-simultaneous assessment, imprecise cholesterol monitoring and screening tests were improved
Costanza, M. C., H. Wolff, et al. (2005), J Clin Epidemiol 58(8): 841-8.
Abstract: OBJECTIVE: To calibrate Reflotron-measured capillary total cholesterol (cTC) relative to a laboratory-measured venous total cholesterol (vTC) criterion standard for monitoring and screening hypercholesterolemia. STUDY DESIGN AND SETTING: Quasi-simultaneous assessment in 1999-2002 of Reflotron cTC and laboratory vTC in a random sample of 4,269 adult residents of Geneva, Switzerland (calibration development subsample n=3,067; validation subsample n=1,172), by means of bias, precision, correlation, sensitivity, and false positive percentage (calculated as 100-specificity) analyses of Reflotron cTC vs. laboratory vTC measures for predicting hypercholesterolemia. RESULTS: Total bias was small (-0.26 mmol/L), but there was substantial negative drift in Reflotron cTC (annual biases +0.08, -0.17, -0.27, and -0.60 mmol/L in 1999-2002). Overall, 57% of Reflotron cTC measurements for 894 hypercholesterolemic patients underestimated laboratory vTC (2%, 57%, 71%, and 98% in 1999-2002). Prior to calibration, sensitivity was 73% for the development and 35% for the validation subsample, with false positive at 4% (development) and 0.1% (validation). After calibration, sensitivity was 78% for the development and 37% for the validation subsample, with false positive at 5% (development) and 0.2% (validation). Using 95% upper prediction limits (UPL) for individual vTC values increased sensitivity to 99% and 83% and false positive percentage to 30% and 7% for the development and validation subsamples, respectively. CONCLUSION: Crude results of Reflotron-measured cTC have poor sensitivity. Instead, 95% UPL can be used for monitoring and screening. Simply adding 0.8 mmol/L to a patient's observed Reflotron cTC value provides a very good approximation to the 95% UPL.

In CCR2-/- mice monocyte recruitment and egress of LDL cholesterol in vivo is impaired
Stein, O., Y. Dabach, et al. (2003), Biochem Biophys Res Commun 300(2): 477-81.
Abstract: Recruitment of macrophages plays an important role in initiation of atheroma, but their involvement in cholesterol clearance during regression is unknown. We developed a mouse model to quantitate cholesterol clearance from a depot of cationized LDL injected into a leg muscle, which evokes a sterile inflammatory reaction. In the CCR2(-/-) mice, cholesterol clearance was significantly slower than in C57BL controls because of decrease in cholesteryl ester (CE) hydrolysis, which is mandatory prior to cholesterol efflux. In CCR2(-/-) mice, macrophage recruitment to the injected site, identified by immunohistochemistry, was markedly delayed. CE hydrolysis was also significantly reduced in thioglycollate elicited peritoneal exudate cells of CCR2(-/-) mice, related to paucity of macrophages in the cell differential. The present study provides definite evidence that recruitment of macrophages is required for LDL cholesterol clearance, which plays a prominent role in regression of an atheroma.

In cholesterol lowering, moderation kills
Esselstyn, C. B., Jr. (2000), Cleve Clin J Med 67(8): 560-4.
Abstract: The high-fat American diet is responsible for an epidemic of coronary artery disease. A plant-based diet with less than 10% fat will prevent coronary disease from developing, halt the progress of existing disease, and even reverse the disease in many patients. Given proper support and education, motivated patients with a history of coronary disease can follow this diet and prevent future cardiac events.

In K562 and HL60 cells membrane ageing during cell growth is associated with changes in cholesterol concentration
Levi, M., P. Wilson, et al. (1997), Mech Ageing Dev 97(2): 109-19.
Abstract: In a cell culture model of aging we have previously shown that there is an age-related decrease in the lipid dynamics of the proerythropoetic K562 cell membranes, as determined by the generalized polarization (GP) of the phase-sensitive lipid probe 2-dimethylamino-6-lauroylnaphthalene (Laurdan) (T. Parasassi, M. Di Stefano, G. Ravagnan, O. Sapora and E. Gratton. Exp. Cell Res., 202 (1992) 432-439). In the present study we also extended our observations to the lymphoblastoid HL60 cell line. In both K562 and HL60 cells during the four days after the last cell culture medium renewal the GP Laurdan value increased in a linear fashion indicating a time-dependent decrease in lipid dynamics. The initial membrane physical properties were almost completely restored upon renewal of the cell culture medium. We measured lipid composition, including individual and total phospholipids, free and esterified cholesterol at the first ('young') and at the fourth ('aged') day after culture medium renewal. We found that the decreased membrane lipid 'fluidity' at the fourth day of cell growth was associated with a 40% increase in cholesterol concentration in both cell lines. This increase in cholesterol concentration was reversible 24 h following the culture medium change. We conclude that in K562 and HL60 cells the 'age-related' decrease in membrane lipid dynamics is mediated by an 'age-related' increase in cell cholesterol content.

In nonhepatic cells, cholesterol 7alpha-hydroxylase induces the expression of genes regulating cholesterol biosynthesis, efflux, and homeostasis
Spitsen, G. M., S. Dueland, et al. (2000), J Lipid Res 41(8): 1347-55.
Abstract: CHO cells expressing the liver-specific gene product cholesterol-7alpha-hydroxylase showed a 6-fold increase in the biosynthesis of (14)Ccholesterol from (14)Cacetate, as well as increased enzymatic activities of 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase and squalene synthase. Cells expressing cholesterol-7alpha-hydroxylase contained less sterol response element-binding protein 1 (SREBP1) precursor, whereas the cellular content of mature SREBP1, as well as the mRNAs of cholesterol biosynthetic genes (HMG-CoA reductase and squalene synthase), were all increased approximately 3-fold. Cells expressing cholesterol-7alpha-hydroxylase displayed greater activities of luciferase reporters containing the SREBP-dependent promoter elements derived from HMG-CoA reductase and farnesyl diphosphate synthase, in spite of accumulating significantly more free and esterified cholesterol and 7alpha-hydroxycholesterol. While cells expressing cholesterol-7alpha-hydroxylase displayed increased SREBP-dependent transcription, sterol-mediated repression of SREBP-dependent transcription by LDL-cholesterol and exogenous oxysterols was similar in both cell types. Cells expressing cholesterol-7alpha-hydroxylase displayed greater rates of secretion of cholesterol as well as increased expression of the ABC1 cassette protein mRNA. Adding 25-hydroxycholesterol to the culture medium of both cell types increased the expression of ABC1 cassette protein mRNA. The combined data suggest that in nonhepatic CHO cells multiple regulatory processes sensitive to cellular sterols act independently to coordinately maintain cellular cholesterol homeostasis.

In search of abnormal enzyme activities of hepatic cholesterol metabolism in patients with cholesterol gallstone disease
Rigotti, A. and F. Nervi (1991), Hepatology 14(6): 1295-7.

In situ hybridization of high density lipoprotein (scavenger, type 1) receptor messenger ribonucleic acid (mRNA) during folliculogenesis and luteinization: evidence for mRNA expression and induction by human chorionic gonadotropin specifically in cell types that use cholesterol for steroidogenesis
Li, X., H. Peegel, et al. (1998), Endocrinology 139(7): 3043-9.
Abstract: The present studies were undertaken to examine the expression of the high density lipoprotein (HDL) receptor, SR-B1 messenger RNA (mRNA) in ovarian cell types during folliculogenesis and luteinization using in situ hybridization histochemistry and to examine its hormonal regulation using Northern blots. For the in situ study for HDL receptor mRNA localization, 21-day-old rats were treated with 50 IU PMSG, and ovaries were collected 0, 24, and 56 h postinjection. At 56 h, animals were treated with a single dose of hCG, and ovaries were subsequently collected at 6-, 12-, 24-, and 72-h and 5-day intervals. In addition, on day 4 of pseudopregnancy, a second dose of 50 IU hCG or saline was administered, and ovaries were collected at 12, 24, and 48 h to determine the induction of the expression of HDL receptor mRNA. The results of in situ hybridization histochemistry showed that in the immature ovary, HDL receptor mRNA is associated with theca interna and interstitial cells (stroma). The mRNA expression in these cell types increased with PMSG treatment, but no signal was detected in the granulosa cells. Northern blot analysis also showed a marked increase in mRNA content in thecal and interstitial cells during follicular development. During luteinization, the intensity of the signal began to appear in the luteinized granulosa cells. With the completion of luteinization, the signal in the corpus luteum tissue became more intense. Further treatment with hCG increased the HDL receptor mRNA content compared with that in the saline-treated control. These results demonstrate that the cholesterol-using cell types of the ovary, namely the interstitial cells, thecal cells, and fully luteinized granulosa cells are endowed with the HDL receptor mRNA, which provides credence to the functional significance of the role of HDL receptor SR-B1 in cholesterol transport and ovarian steroidogenesis.

In situ localization of cholesterol in skeletal muscle by use of a monoclonal antibody
Clarke, M. S., C. R. Vanderburg, et al. (2000), J Appl Physiol 89(2): 731-41.
Abstract: A common perception is that cholesterol, the major structural lipid found in mammalian membranes, is localized nearly exclusively to the plasma membrane of living cells and that it is found in much smaller quantities in internal membranes. This perception is based almost exclusively on cell fractionation studies, in which density gradient centrifugation is used for purification of discrete subcellular membrane fractions. Here we describe a monoclonal antibody, MAb 2C5-6, previously reported to detect purified cholesterol in synthetic membranes (Swartz GM Jr, Gentry MK, Amende LM, Blanchette-Mackie EJ, and Alving CR. Proc Natl Acad Sci USA 85: 1902-1906, 1988), that is capable of detecting cholesterol in situ in the membranes of skeletal muscle sections. Localization of cholesterol, the dihydropyridine receptor of the T tubule, and the Ca(2+)-ATPase of the sarcoplasmic reticulum (SERCA2) by means of double and triple immunostaining protocols clearly demonstrates that cholesterol is primarily localized to the sarcoplasmic reticulum membranes of skeletal muscle rather than the sarcolemmal or T tubule membranes. The availability of this reagent and its ability to spatially localize cholesterol in situ may provide a greater understanding of the relationship between membrane cholesterol content and transmembrane signaling in skeletal muscle.

In this issue: genetics, cholesterol, and the risk of Alzheimer's disease
Reiman, E. M. (2005), J Clin Psychiatry 66(7): 938-9.

In vitro and in vivo evidence for the role of HDL in reverse cholesterol transport
Pieters, M. N., D. Schouten, et al. (1994), Biochim Biophys Acta 1225(2): 125-34.

In vitro and in vivo transfection of melanoma cells B16-F10 mediated by cholesterol-based cationic liposomes
Reynier, P., D. Briane, et al. (2002), J Drug Target 10(7): 557-66.
Abstract: In vitro and in vivo transgene expression in B16-F10 melanoma cells has been investigated using an original cationic liposome prepared with triethyl aminopropane carbamoyl cholesterol iodide (TEAPC-Chol) as carrier. TEAPC-Chol/DOPE (dioleoyl phosphatidyl ethanolamine) liposomes are unilamellar, very stable and not toxic in the used concentration range. The yield in complexation with plasmid DNA can reach 100% even in the presence of fetal calf serum. The transfection level has been evaluated by luminometric measurements of luciferase expression. With TEAPC-Chol/DOPE (1:1) liposomes, a relatively high transfection level in B16-F10 cells has been observed comparing to commercial reagents. For in vivo assays, the transfection level in tumors induced in Nude mice has been optimized by studying the effects of charge ratio, of the helper lipid and of the injection volume. Results showed that TEAPC-Chol/DOPE (1:1) liposomes have improved 10-fold transfection level versus direct gene transfer of free DNA.

In vitro characterization of two types of LDL apheresis module and effect of repetitive LDL apheresis on plasma cholesterol levels and aortic atherosclerosis in heterozygous WHHL rabbits
Kim, S. S., Y. Kutsumi, et al. (1991), Jpn Circ J 55(1): 68-80.
Abstract: In vitro filtration was used to characterize and compare the function of two types of LDL apheresis module: membrane filtration (module M: pore diameter, 0.04 micron; effective surface area, 0.1 m2) and LDL adsorption (module A: a column containing 20 ml of polyvinyl alcohol gels fixed with polyacrylic acid). Module A had better selectivity of LDL removal, while module M could rapidly remove a larger amount of LDL. The effect of repetitive LDL apheresis with module A on the plasma cholesterol level and on the development of aortic atherosclerosis was examined in 6 heterozygous WHHL rabbits (5 to 10 months old; mean plasma total cholesterol level, 270 +/- 39 mg/dl), treated with LDL apheresis at weekly intervals for 2 months. Plasma total and LDL cholesterols were lowered approximately 40% by a signal procedure. The LDL cholesterol level tended to decrease as treatment progressed, while the HDL cholesterol level was unchanged or rose above the baseline value in a week after LDL apheresis. The ratio of atherosclerotic lesion area to whole aortic area was relatively low in treated rabbits (6.5 +/- 1.9%) in comparison with that in 5 untreated heterozygous WHHL rabbits (18.3 +/- 7.7%). The mean cholesterol content in the thoracic aorta was 4.9 +/- 1.3 mg/g wet tissue in treated rabbits vs 13.3 +/- 6.1 mg/g wet tissue in untreated rabbits. These results suggest that repetitive LDL apheresis might be effective in maintaining a lower level of LDL cholesterol and retarding the atherosclerotic process in vivo.

In vitro complex formation between cholesterol and alpha 1-proteinase inhibitor
Janciauskiene, S. and S. Eriksson (1993), FEBS Lett 316(3): 269-72.
Abstract: The in vitro interaction between human alpha 1-proteinase inhibitor (alpha 1-PI) and cholesterol was studied with electrophoretic and gel chromatographic methods. The addition of cholesterol (from 1 to 20 mol/mol alpha 1-PI) at 37 degrees C resulted in retarded electrophoretic mobility of alpha 1-PI towards the anode, diminished immunoreactivity and antiproteinase activity. At a molar ratio of 2:1 (cholesterol/alpha 1-PI), antitryptic activity was reduced by 15% but antielastase activity by 50%. At this ratio the gel filtration alpha 1-PI peak appeared at 67 kDa, as compared to 52 kDa for native alpha 1-PI. No size difference was noted on SDS-PAGE. These results suggest the occurrence of noncovalent complex formation between cholesterol and alpha 1-PI in vitro.

In vitro determination by 1H-NMR studies that bile with shorter nucleation times contain cholesterol-enriched vesicles
Sequeira, S. S., H. G. Parkes, et al. (1995), Biochim Biophys Acta 1256(3): 360-6.
Abstract: Although biliary vesicles are considered to be the primary source of cholesterol found in cholesterol gallstones, difficulties in quantitatively separating the different cholesterol transport modes in bile still remain. Proton nuclear magnetic resonance spectroscopy (1H-NMR) offers an alternative approach. Investigations were carried out on both model biles and human gallbladder bile samples: (i) to follow the effect of increasing sodium glycocholate concentrations on the 1H-NMR spectra of arachidonic acid rich-phospholipid, and cholesterol-lecithin vesicles, (ii) to compare the concentrations of total phospholipids in bile determined enzymatically with those obtained by integration of the phospholipid choline head group resonance peak, and (iii) to examine the relationship between biliary cholesterol nucleation time (NT) and the areas of the biliary lipid 1H-NMR peaks. It was found that the molecular motions of vesicle phospholipid, as determined by 1H-NMR, were restricted by saturation with cholesterol. In bile from patients with cholesterol gallstones, the reduced NMR fluidity of the phospholipid choline-head group indicated that the proportion of cholesterol-phospholipid vesicles containing more than 50% cholesterol, on a molar basis, was increased. The ratios of the N+(CH3)3 and = CH proton resonance peaks showed no overlap between samples with cholesterol gallstones and shorter NT and those with either no gallstones or pigment stones and longer NT. 1H-NMR spectroscopy indicates in a non-invasive manner those biles which are prone to cholesterol crystal formation.

In vitro dissolution of cholesterol and brown pigmented gallstones: a comparison of MTBE, DMSO and BA-EDTA
Cheng, J. S., K. H. Lai, et al. (2000), Zhonghua Yi Xue Za Zhi (Taipei) 63(9): 667-72.
Abstract: BACKGROUND: Gallstones are a common problem in Taiwan and surgical removal remains the essential treatment. Successful dissolution of the stones with chemical solutions and then removal by endoscopic or percutaneous methods have previously been reported. We designed this study to find the ideal agent for dissolving gallstones. METHODS: Twelve chemical solutions with dimethylsulfoxide (DMSO), methyl tert-butyl ether (MTBE) and ethylenediamine tetra-acetic acid (EDTA) in different mixtures were tested to investigate their ability to dissolve gallstones in vitro. The dissolution of stones was performed at 37 degrees C and each procedure was repeated five to seven times. RESULTS: The solvent containing DMSO/MTBE (1/1) had a higher dissolving capacity for cholesterol stones, with solubility reaching 96.8% after 6 hours. The solution containing DMSO/MTBE (7/3) had the maximal solubility for calcium bilirubinate stones, with solubility reaching 22.9% after 6 hours. Also, we found that the intact stones of calcium bilirubinate became fragmented after treatment with the DMSO/MTBE solution without stirring. CONCLUSIONS: The DMSO, MTBE and EDTA agents that we used effectively dissolved gallstones, especially cholesterol stones, in vitro. Further in vivo studies are necessary to confirm the efficacy and safety of these solvents before clinical application.

In vitro dissolution of cholesterol gallstones
Sternal, R. S. and M. A. Davis (1992), Invest Radiol 27(12): 1040-3.
Abstract: RATIONALE AND OBJECTIVES. Methyl tert-butyl ether (MTBE) is the solvent most commonly used for in vivo dissolution of cholesterol gallstones. Its limitations, however, include high volatility and flammability along with potential toxicologic concerns. Therapy may take several hours. This study was initiated to identify alternate solvents which may be superior to MTBE in one or more of these areas. METHODS. MTBE was compared with several other solvents for cholesterol-dissolving capacity. Groups of human cholesterol gallstones were placed in test tubes, and, without agitation, subjected to mixtures of MTBE:ethanol or another solvent:ethanol. RESULTS. Six other solvents were found to have higher capacities. In several cases, other solvent mixtures dissolved gallstones up to twice as fast as the MTBE:ethanol mixture. These faster solvents were cyclic ethers (tetrahydrofuran THF, methyl tetrahydrofuran MTHF, tetrahydropyran THP, methyl tetrahydropyran MTHP, and possibly dimethyl tetrahydrofuran DMTHF) and limonene. Some of these solvents also have lower volatility and higher flash points than MTBE, resulting in safer storage and handling. THF and pyridine, however, were found to precipitate bile components when mixed with bile. CONCLUSION. The authors describe solvents that may be superior to MTBE for rapid dissolution of gallstones in vivo.

In vitro effect of cholesterol on calcifying activity of vesicles isolated from rabbit aortas
Hsu, H. H. (2003), Biochim Biophys Acta 1638(3): 235-40.
Abstract: It has been shown that vesicles play a key role in the onset mechanism of aortic calcification related to cholesterol-induced atherosclerosis. This study using a rabbit model was conducted to determine whether cholesterol exerts a direct effect on vesicle's calcifiability. Inclusion of cholesterol in calcifying media stimulated ATP-initiated deposition of calcium in a dose-dependent manner by vesicles isolated from normal aortas using crude collagenase digestion. By contrast, cholesterol did not significantly affect ATP-promoted calcification if vesicles were isolated from atherosclerotic aortas. To determine whether high cholesterol levels in atherosclerotic vesicle preparations may have already maximized calcifying activity and therefore account for lack of the vesicle's response to the sterol, Fourier transform infrared spectroscopy (FT-IR) was used to compare the cholesterol contents in control and atherosclerotic vesicles. The spectral patterns revealed higher levels of cholesterol in vesicle preparations from atherosclerotic aortas than those from normal aortas. Removal of extra-vesicular cholesterol micelles from atherosclerotic vesicles by a relatively low centrifugal force sensitized the vesicles to cholesterol stimulation causing a 2-fold increase in calcifying activity. Of various oxidized forms of cholesterol tested, 7-keto and 6-keto cholesterol enhanced the activity by 2-fold. Altogether, these observations suggest that cholesterol and especially its oxidized forms may induce aortic calcification by directly enhancing the vesicle's ability to calcify.

In vitro effects of fat, FA, and cholesterol on sphingomyelin hydrolysis induced by rat intestinal alkaline sphingomyelinase
Liu, J. J., A. Nilsson, et al. (2002), Lipids 37(5): 469-74.
Abstract: Dietary sphingomyelin (SM) may have regulatory effects on cell proliferation and tumorigenesis in the colon. Alkaline sphingomyelinase (SMase) is the major enzyme responsible for hydrolysis of SM in the gut. Previously we purified the enzyme and showed that the presence of glycerophospholipids inhibited SM hydrolysis induced by alkaline SMase in vitro. In the present work, we studied the effects of TG, DG, FA, ceramide, and cholesterol on SM hydrolysis catalyzed by purified alkaline SMase. The results showed that both TG (triolein and tristearin) and DG (1,2-dioleoyl-sn-glycerol and 1,2-distearoyl-rac-glycerol) inhibited the activity of alkaline SMase. 1-Monooleoyl-rac-glycerol, 1-monostearoyl-rac-glycerol, stearic acid, oleic acid, linoleic acid, linolenic acid, and arachidonic acid stimulated the activity of alkaline SMase at 0.4-0.8 mM concentrations but inhibited the enzyme at higher concentrations. There was no difference between the effects induced by saturated and unsaturated FA. A short-chain FA such as lauric acid had a stronger stimulatory effect at low concentrations and weaker inhibitory effect at high concentrations than long-chain FA. Choosing linoleic acid as an example, we found that FA had similar effects on both alkaline SMase and neutral SMase. Cholesterol and ceramide when mixed with FA to increase its solubility in bile salt micelles inhibited SMase activity. In conclusion, glycerides, FA, ceramide, and cholesterol influence SM hydrolysis catalyzed by intestinal alkaline SMase. The presence of lipids in the diet may thus influence the course of SM digestion in the gut and thereby the exposure of colon to SM metabolites.

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Cholesterol Journal Articles