| For medical practitioners and the general public - Cholesterol Journal Article Catalog. |
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| Ischemic optic neuropathy as the first manifestation of elevated cholesterol levels in young patients Deramo, V. A., R. C. Sergott, et al. (2003), Ophthalmology 110(5): 1041-6; discussion 1046. Abstract: PURPOSE: To investigate the relationship between idiopathic nonarteritic ischemic optic neuropathy (NAION) and serum lipid levels in patients /= 240 mg/dl) with NAION was 3.3 (95% confidence interval, 1.4-7.8), and the likelihood increased when the comparison was restricted to nondiabetic patients. Diabetes mellitus was more common in cases than controls (P = 0.027), but systemic hypertension was not significantly different (P = 0.63). No patient (0 of 24) had a magnetic resonance imaging study consistent with optic neuritis or central nervous system demyelination. Visual improvement was uncommon. CONCLUSIONS: This study demonstrates that hypercholesterolemia is associated with NAION in younger patients. NAION may be the first manifestation of a lipid disorder, a previously unrecognized syndrome. These patients have experienced a focal, microvascular central nervous system ischemic event at a relatively young age. Aggressive treatment of lipid abnormalities in these patients may be warranted. |
| Isoflavone aglycone-rich extract without soy protein attenuates atherosclerosis development in cholesterol-fed rabbits Yamakoshi, J., M. K. Piskula, et al. (2000), J Nutr 130(8): 1887-93. Abstract: The antiatherogenic effect of soy protein with intact isoflavones is well established, but the effects of isoflavones without soy protein have not been determined. We investigated the antiatherogenic effect of an isoflavone aglycone-rich extract (containing 429.4 mg/g isoflavone aglycones) without soy protein from fermented soy in cholesterol-fed rabbits. We fed 12-wk-old New Zealand white male rabbits diets containing 1 g/100 g cholesterol with 0, 0.33 or 1 g/100 g isoflavone aglycones for 8 wk. We also fed the rabbits a diet containing 1 g/100 g cholesterol with 1.09 g/100 g soy saponin-rich extract, a component other than isoflavone aglycones in the isoflavone aglycone-rich extract. Controls did not consume cholesterol, isoflavone aglycones or saponins. The isoflavone aglycone- and saponin-rich extracts did not affect the serum lipid profile of cholesterol-fed rabbits. The serum concentration of daidzein in its conjugated form was significantly higher in the high isoflavone group than in the low isoflavone group. The level of cholesteryl ester hydroperoxide (ChE-OOH) induced by CuSO(4) in plasma in the high isoflavone group was significantly less than that in the cholesterol group, and the ChE-OOH levels of LDL in the low and high isoflavone groups were significantly less than those in the cholesterol group. The ChE-OOH levels in plasma and LDL in the saponin group did not differ from the cholesterol group. In the aortic arch, the cholesterol concentration was significantly lower in the high isoflavone group, and malondialdehyde concentration was significantly lower in the low and high isoflavone groups compared with the cholesterol group; however these concentrations in the saponin group did not differ from those in the cholesterol group. The atherosclerotic lesion area of the aortic arch was significantly lower in the isoflavone groups (26.3% lower in the low isoflavone group and 36.9% lower in the high isoflavone group) than in the cholesterol group. The lesion areas were not different in the soy saponin and cholesterol groups. Immunohistochemical analysis revealed fewer oxidized LDL-positive macrophage-derived foam cells in atherosclerotic lesions in the aortic arch of isoflavone groups compared with that of the cholesterol group. These results suggest that the antioxidative action of isoflavones and their antioxidative metabolites inhibit the oxidation of LDL, thereby exerting an antiatherosclerotic effect. |
| Isoflavone-free soy protein prepared by column chromatography reduces plasma cholesterol in rats Fukui, K., N. Tachibana, et al. (2002), J Agric Food Chem 50(20): 5717-21. Abstract: To know whether isoflavones are responsible for the hypocholesterolemic effect of soy protein, the effect on plasma cholesterol of isoflavone-free soy protein prepared by column chromatography was examined in rats. Five-week-old male Sprague-Dawley rats were fed cholesterol-enriched AIN-93G diets containing either 20% casein (CAS), 20% soy protein isolate (SPI), 20% isoflavone-free SPI (IF-SPI), 19.7% IF-SPI + 0.3% isoflavone-rich fraction (isoflavone concentrate, IC), or 20% CAS + 0.3% IC for 2 weeks. Plasma total cholesterol concentrations of rats fed SPI and IF-SPI were comparable and were significantly lower than that of rats fed CAS. The addition of IC to the CAS and IF-SPI did not influence plasma cholesterol level. Fecal steroid excretion of the three SPI groups was higher than that of the two CAS groups, whereas the addition of IC showed no effect. Thus, a significant fraction of the cholesterol-lowering effect of SPI in rats can be attributed to the protein content, but the isoflavones and other minor constituents may also play a role. |
| Isoform-dependent cholesterol efflux from macrophages by apolipoprotein E is modulated by cell surface proteoglycans Hara, M., T. Matsushima, et al. (2003), Arterioscler Thromb Vasc Biol 23(2): 269-74. Abstract: OBJECTIVE: Apolipoprotein E (apoE) mediates cellular cholesterol efflux and plays a crucial role in the inhibition of atherogenesis. We investigated whether there is an isoform-specific difference in its function for cholesterol efflux from cholesterol-loaded RAW264.7 cells, a murine macrophage cell line that lacks endogenous apoE expression. METHODS AND RESULTS: When human apoE was expressed in RAW264.7 cells, apoE2 reduced cellular total cholesterol (TC) and esterified cholesterol (EC) levels significantly, whereas apoE3 and apoE4 had no effect. However, treatment of cells with 4-methylumbelliferyl-7-beta-D-xyloside (beta-DX) resulted in all 3 isoforms' reducing cellular TC and EC contents significantly. We also investigated the effect of exogenously derived apoE on cholesterol efflux by utilizing the medium harvested from HeLa cells expressing apoE. ApoE2 and E3 reduced both cellular TC and EC contents significantly, whereas apoE4 did not. However, treatment of the cells with beta-DX resulted in all 3 exogenously derived apoE isoforms' reducing TC and EC contents significantly. The binding ability of apoE to heparan sulfate proteoglycans examined by heparinase I treatment revealed less binding ability of apoE2 compared with that of apoE3 or apoE4. CONCLUSIONS: The present study clarified the differential cellular cholesterol-modulating effect of apoE isoforms in macrophages, which would be due to the difference in their binding to proteoglycans. |
| Isolated low HDL cholesterol as a risk factor for coronary heart disease mortality. A 21-year follow-up of 8000 men Goldbourt, U., S. Yaari, et al. (1997), Arterioscler Thromb Vasc Biol 17(1): 107-13. Abstract: For the purpose of screening individuals at high risk for coronary heart disease (CHD), serum total cholesterol (TC) of 5.2 mmol/L, has been set as a value dividing "desirable" from intermediate high or elevated levels, and HDL cholesterol (HDL-C) < 0.9 mmol/L has been labeled as abnormally low, implying high CHD risk. It has been conjectured that low HDL-C poses no risk in the absence of elevated LDL cholesterol or TC. To assess the risk of CHD-free men with "isolated low HDL-C," ie, abnormally low HDL-C with desirable TC, we examined the CHD and all-cause mortality of some 8000 Israeli men aged 42 years and older during 1965 through 1986. Men with isolated low HDL-C represented one sixth of the cohort. CHD mortality among these men was 36% higher (age adjusted) than in counterparts with desirable TC, of which > 0.9 mmol/L was contained in the high-density fraction. In men with TC > 5.2 mmol/L, abnormally low HDL-C was associated with a virtually identical CHD mortality risk ratio, 38%. These findings persisted after adjustment for multiple CHD risk factors. The excess CHD risk associated with isolated low HDL-C appeared particularly increased in men with diabetes mellitus, whose death rate was 65% higher than in diabetics with HDL-C > 0.9 mmol/L. A second subgroup result was consistent with equal CHD mortality risk among men in the "desirable" TC range, with or without low HDL-C, if systolic blood pressure was > 160 mm Hg. These are post hoc findings, and hypotheses arising from these observations would require independent examination. Total mortality was not increased in men with isolated low HDL-C compared with men who had HDL-C < 0.9 mmol/L and TC > 5.2 mmol/L at baseline. These results indicate that an increased risk of CHD death is associated with abnormally low HDL-C for cholesterol ranges both below and above 5.2 mmol/L. For the individual, therefore, the risk is multiplied by the same amount regardless of TC. Quitting smoking, increasing physical activity, and decreasing body weight would all contribute to raise HDL-C in individuals of most or all age groups. When examined from a community perspective, the results are consistent with a relatively low population-attributable fraction among CHD-free men. This would tend to support the recommended practice of considering a TC level of 5.2 mmol/L (200 mg/dL) as a threshold for further evaluation in screened individuals without manifest CHD. |
| Isolated low HDL cholesterol. An insulin-resistant state Karhapaa, P., M. Malkki, et al. (1994), Diabetes 43(3): 411-7. Abstract: High levels of very-low-density lipoprotein (VLDL) triglycerides (TGs) and low levels of high-density lipoprotein (HDL) cholesterol have been found to be associated with insulin resistance. However, direct evidence that patients with isolated low HDL cholesterol are insulin resistant is still lacking. Therefore, we investigated the degree of insulin resistance and intracellular metabolism of glucose by the euglycemic glucose clamp technique and indirect calorimetry in three groups of subjects with normal glucose tolerance: 17 male control subjects with normolipidemia, 12 male patients with isolated low HDL cholesterol (low HDL group), and 10 male patients with low HDL cholesterol and hypertriglyceridemia (low HDL/high TG group). Fasting, 1-h, and 2-h glucose levels did not differ between the groups in an oral glucose tolerance test (OGTT). In contrast, insulin levels during an OGTT were significantly higher in the low HDL group than in the control group (fasting insulin: 85 +/- 11 vs. 50 +/- 6 pM, P = 0.005; 1-h insulin: 622 +/- 92 vs. 394 +/- 64 pM, P = 0.004; and 2-h insulin: 343 +/- 73 vs. 194 +/- 40 pM, P = 0.006). Similarly, insulin levels were also higher in the low HDL/high TG group than in the control group (fasting insulin: 82 +/- 14 pM, P = 0.037; 1-h insulin: 795 +/- 179 pM, P = 0.063; and 2-h insulin: 488 +/- 145 pM, P = 0.040).(ABSTRACT TRUNCATED AT 250 WORDS) |
| Isolated low HDL cholesterol: an insulin-resistant state only in the presence of fasting hypertriglyceridemia Tai, E. S., S. C. Emmanuel, et al. (1999), Diabetes 48(5): 1088-92. Abstract: Individuals with isolated low HDL cholesterol are at increased risk of coronary artery disease. It has been reported previously that this is an insulin-resistant state. We analyzed data from the 1992 Singapore National Health Survey with the objective of defining the clinical and metabolic parameters associated with isolated low HDL cholesterol. A total of 3,568 individuals were selected by stratified random sampling. Subjects with low HDL cholesterol (<0.9 mmol/l) and "ideal" total cholesterol (<5.2 mmol/l) were identified. Data on anthropometry, blood pressure (BP), insulin resistance, glucose tolerance, sex, smoking habit, and ethnic group were examined. We found that this group was heterogeneous. Those with fasting triglyceride (TG) >1.7 mmol/l (low HDL/high TG) displayed features of the insulin resistance syndrome characterized by obesity, higher diastolic BP, greater insulin resistance, and a greater tendency to have diabetes or impaired glucose tolerance (IGT). If fasting TG was <1.7 mmol/l (isolated low HDL cholesterol), individuals were similar to the general population in terms of insulin resistance and obesity. Both groups were more commonly men and Asian Indian. The ethnic difference in prevalence could not be explained by differences in diet, exercise, alcohol ingestion, or smoking. Our data support the view that Asian Indians are genetically predisposed to isolated low HDL cholesterol as well as the insulin resistance syndrome. The higher prevalence of isolated low HDL cholesterol, the young age at which individuals exhibit this phenotype (mean age 32.5 years), along with the greater propensity for Asian Indians to develop insulin resistance and IGT contribute to the threefold increased incidence of myocardial infarction in those <65 years of age in this ethnic group. |
| Isolated low HDL-cholesterol as an important risk factor for coronary heart disease Miller, M. and P. O. Kwiterovich, Jr. (1990), Eur Heart J 11 Suppl H: 9-14. Abstract: Decreased levels of high density lipoprotein (HDL)-cholesterol are found in patients with hypertriglyceridaemia and in patients who have inherited disorders associated with premature coronary heart disease. Hereditary conditions associated with low levels of HDL-cholesterol and normal total cholesterol levels include familial hypoalphalipoproteinaemia, Tangier disease, fish eye disease, and lecithin: cholesterol acyltransferase deficiency. Secondary causes of low HDL-cholesterol levels include any condition that affects liver metabolism. A recent study of patients with coronary artery disease (CAD) who had normal levels of low density lipoprotein cholesterol and total cholesterol revealed that two-thirds of the men and four-fifths of the women had low HDL-cholesterol levels, suggesting that low HDL-cholesterol may be more prevalent than previously suspected. The high incidence of isolated hypoalphalipoproteinaemia in this group indicates that HDL-cholesterol measurements should be performed on all patients with CAD, regardless of their total cholesterol levels. |
| Isolation and characterization of a cholesterol crystallization promoter from human bile Abei, M., P. Kawczak, et al. (1993), Gastroenterology 104(2): 539-48. Abstract: BACKGROUND: Recent studies on the pathogenesis of cholesterol gallstone disease have focused on the potential importance of an imbalance between biliary proteins having either inhibitory or promoting activities on nucleation and/or growth of cholesterol crystals as the initial stage in stone formation. The current study describes the purification and partial characterization of a 42-kilodalton biliary glycoprotein that shows concentration-dependent cholesterol crystallization-promoting activity. METHODS: Chromatographic methods were used for separation and purification. Characterization steps included electrophoresis, deglycosylation, amino acid and carbohydrate analysis, and activity analysis by crystal growth assay. RESULTS: The 42-kilodalton purified glycoprotein is an extensively glycosylated (37%) monomer with an acidic isoelectric point (pl < 4.1) that is probably based on the sialic acid content of the carbohydrate moiety. Enzymatic N-deglycosylation removes the carbohydrate moiety and inactivates the promoting activity. Furthermore, enzymatic proteolysis results in both its complete structural degradation and functional inactivation. Although the glycoprotein was isolated from normal human gallbladder biles, its presence in gallstone-associated samples is clearly shown. CONCLUSIONS: This report outlines biochemical features of a human biliary glycoprotein that may be of major pathophysiological significance in gallstone disease. |
| Isolation and characterization of calmodulin-inactivating cholesterol hydroperoxides Tipton, C. L., M. Shih, et al. (1991), J Lipid Res 32(9): 1403-8. Abstract: A series of cholesterol hydroperoxides has been prepared and tested as inactivators of calmodulin. Two previously undescribed compounds, tentatively identified as 20-(R)-25-dihydroperoxy-5-cholesten-3 beta-ol and its 20-(S) isomer inactivate calmodulin with 50% loss of activity at 5-10 microM. Cholesterol derivatives with a single hydroperoxy group at C-20 or C-25 are less effective, while 7 alpha-hydroperoxy-cholesterol and 25-hydroxy-cholesterol are inactive. The side-chain hydroperoxide compounds were isolated from a mixture shown earlier to suppress formation of fatty streaks in aortas of rabbits fed a diet supplemented with cholesterol. |
| Isolation and characterization of Chinese hamster ovary cell mutants defective in intracellular low density lipoprotein-cholesterol trafficking Cadigan, K. M., D. M. Spillane, et al. (1990), J Cell Biol 110(2): 295-308. Abstract: This paper reports the isolation and characterization of Chinese hamster ovary cell mutants defective in low density lipoprotein (LDL)-cholesterol trafficking. The parental cell line was 25-RA, which possesses LDL receptors and various cholesterogenic enzyme activities that are partially resistant to down regulation by exogenous sterols (Chang, T. Y., and J. S. Limanek. 1980. J. Biol. Chem. 255:7787-7795). Because these cells accumulate a large amount of intracellular cholesteryl ester when grown in medium containing 10% fetal calf serum, mutagenized populations of 25-RA cells were grown in the presence of a specific inhibitor of acyl-coenzyme A: cholesterol acyltransferase (ACAT), which depleted their cholesteryl ester stores. Without this cholesterol ester storage, 99% of 25-RA cells die after 5-d growth in cholesterol starvation medium, while the mutant cells, which accumulate free cholesterol intracellularly, survived. In two mutant clones chosen for characterization, activation of cholesteryl ester synthesis by LDL was markedly reduced in the mutant cells compared with 25-RA cells. This lack of activation of cholesterol ester synthesis in the mutant cells could not be explained by defective uptake and/or processing of LDL or by a decreased amount of ACAT, as determined by in vitro enzyme activity. Mutant cells grown in the presence of LDL contain numerous cytosolic particles that stain intensely with the fluorescent compound acridine orange, suggesting that they are acidic. The particles are also stained with filipin, a cholesterol-specific fluorescent dye. Indirect immunofluorescence with a monoclonal antibody specific for a lysosomal/endosomal fraction revealed a staining pattern that colocalized with the filipin signal. The mutant phenotype was recessive. The available evidence indicates that the mutant cells can take up and process LDL normally, but the hydrolyzed cholesterol accumulates in an acidic compartment, probably the lysosomes, where it can not be transported to its normal intracellular destinations. |
| Isolation and characterization of Chinese hamster ovary cells defective in the intracellular metabolism of low density lipoprotein-derived cholesterol Dahl, N. K., K. L. Reed, et al. (1992), J Biol Chem 267(7): 4889-96. Abstract: We have isolated clones of an established cell line which express defects in intracellular cholesterol metabolism. Chinese hamster ovary cells were mutagenized, and clones unable to mobilize low density lipoprotein (LDL)-derived cholesterol to the plasma membrane were selected. Biochemical analysis of two mutant clones revealed a phenotype characteristic of the lysosomal storage disease, Niemann-Pick type C. The mutant cell lines were found to be defective in the regulatory responses elicited by LDL-derived cholesterol. LDL-mediated stimulation of cholesterol esterification was grossly defective, and LDL suppression of 3-hydroxy-3-methylglutaryl-CoA reductase was impaired. However, the mutants modulated these activities normally in response to 25-hydroxycholesterol or mevalonate. The LDL-specific defects were predicated by the inability of these mutants to mobilize LDL-derived cholesterol from lysosomes. Cell fractionation studies showed that LDL-derived, unesterified cholesterol accumulated in the lysosomes of mutant cells to significantly higher levels than normal, commensurate with defective movement of cholesterol to other cellular membranes. Characterization of cell lines defective in intracellular cholesterol transport will facilitate identification of the gene(s) required for intracellular cholesterol movement and regulation. |
| Isolation and characterization of cholic acid 7alpha-dehydroxylating fecal bacteria from cholesterol gallstone patients Wells, J. E., F. Berr, et al. (2000), J Hepatol 32(1): 4-10. Abstract: BACKGROUND/AIMS: The development of cholesterol gallstones, in some patients, has been associated with increased proportions of deoxycholic acid in the bile acid pool. Deoxycholic acid is a microbial product of cholic acid 7alpha-dehydroxylation in the intestines. The levels and activities of bile acid 7alpha-dehydroxylating bacteria have been reported to be increased in gallstone patients. The aim of the current study was to isolate 7alpha-dehydroxylating bacteria from gallstone patients and determine if these individuals are colonized by similar bacterial species. METHODS: The levels of 7alpha-dehydroxylating bacteria in fecal samples were determined by fecal dilutions in 24 gallstone patients and 10 controls. 7alpha-Dehydroxylating bacteria were isolated by a non-selective streak plate technique and 7alpha-dehydroxylation activity was determined by measuring the conversion of 14C-cholic acid to 14C-deoxycholic acid using thin-layer chromatography. RESULTS: Gallstone patients had >42-fold (p<0.01) higher levels of 7alpha-dehydroxylating bacteria than patients who had not developed gallstones. Eighteen strains of 7alpha-dehydroxylating bacteria were isolated from eight gallstone patients. Attempts to isolate 7alpha-dehydroxylating bacteria from ten control patients were unsuccessful using identical isolation techniques. Surprisingly, all strains of bacteria isolated from gallstone patients appear to belong to the genus Clostridium. CONCLUSION: Gallstone patients have higher levels of 7alpha-dehydroxylating fecal bacteria and appear to harbor only members of the genus Clostridium with this activity. |
| Isolation and lipid characterization of cholesterol-enriched fractions in cortical and nuclear human lens fibers Rujoi, M., J. Jin, et al. (2003), Invest Ophthalmol Vis Sci 44(4): 1634-42. Abstract: PURPOSE: Human lens membranes contain unusually high levels of cholesterol and sphingolipids, lipids known to segregate into liquid-ordered domains. The current study was conducted to pursue the determination and characterization of these domains in membranes of clear and cataractous human lenses. METHODS: Cortical and nuclear regions of aged clear and cataractous lenses were obtained. After lysis with Triton X-100 at 4 degrees C and sucrose linear-density centrifugation, sedimenting and nonsedimenting fractions (when present) were collected. Phospholipids were analyzed by (31)P-nuclear magnetic resonance (NMR) and mass spectrometry. Caveolae and raft markers were tested by Western blot analysis. RESULTS: Only samples from clear lenses exhibited a nonsedimenting band. Phospholipid contents were comparable for sedimenting fractions of clear and cataractous membranes. Cholesterol to phospholipid molar ratios in light-density bands were nearly 7, three times greater than in sedimenting fractions. The portion of total cholesterol present in nonsedimenting fractions increased from 5.5% in the cortex to 14% in the nucleus. Two lysophospholipids comprising approximately 10% of all phospholipids in total membranes were undetectable in nonsedimenting fractions. Caveolin-1 was enriched in these fractions. CONCLUSIONS: Phospholipid compositional differences between lighter and heavier fractions from clear lenses were relatively minor and could not, alone, account for the substantial enrichment of cholesterol in the lighter fractions. Specific proteins, such as caveolin-1, must recruit cholesterol and induce clustering. Undetectable amounts of light-density domains in cataractous membranes suggest either disruption of these aggregates and thus the function of proteins within them, possibly relevant to lens transparency, and/or greater density of these clusters due to stronger binding of insoluble crystallins to membranes. |
| Isolation and partial characterization of cholesterol pronucleating hydrophobic glycoproteins associated to native biliary vesicles Miquel, J. F., L. Nunez, et al. (1993), FEBS Lett 318(1): 45-9. Abstract: Cholesterol is transported both in unilamellar phosphatidylcholine vesicles and in bile salts-mixed micelles in native bile. The vesicular carrier of biliary lipids apparently has a well defined protein profile with a potent cholesterol crystallization-promoting activity. This study was conducted to identify and further characterize these vesicular proteins and to test the effect of isolated vesicular proteins on the cholesterol crystal formation in supersaturated model bile. The results confirmed that proteins are a constant component of highly purified biliary vesicles both in hepatic and gallbladder bile. Immunoglobulins (IgA, IgG and IgM) and albumin are associated to the purified hepatic biliary vesicles. Furthermore, four different hydrophobic glycoproteins with a molecular mass of 130, 114, 86, and 62-67 kDa were isolated. These glycoproteins showed no reactivity with anti-human whole serum or anti-immunoglobulin antibodies, suggesting that these proteins are biliary-specific. Isolated 130, 114 and 62-67 kDa vesicular glycoproteins significantly decreased the cholesterol nucleation time in artificial model bile. We concluded that some, but not all, vesicular-bound hydrophobic glycoproteins have cholesterol pronucleating activity and they may be involved in the pathogenesis of cholesterol gallstone disease. |
| Isolation and purification of human biliary vesicles with potent cholesterol-nucleation-promoting activity Miquel, J. F., A. Rigotti, et al. (1992), Clin Sci (Lond) 82(2): 175-80. Abstract: 1. Cholesterol nucleation is a critical step in the formation of cholesterol gallstones. This nucleation takes place after aggregation and fusion of cholesterol-rich biliary vesicles, a process probably modulated by biliary proteins. The present study was conducted to identify specific proteins associated with native cholesterol-rich biliary vesicles and to explore their effect on the cholesterol-nucleation time of supersaturated artificial bile. 2. Hepatic bile was obtained from six patients with cholesterol gallstone disease. Biliary vesicles were isolated by ultracentrifugation and were purified by gel filtration chromatography. A small amount of protein (less than 1% by weight) remained associated with the purified cholesterol-rich biliary vesicles. The electrophoretic profile of these proteins was remarkably similar in all six patients, showing the presence of at least six polypeptides (of molecular mass from 52 to 200 kDa), five of them having carbohydrate residues (except the 52 kDa one). The effect of reconstituted biliary vesicle solutions, containing their specific vesicular proteins, on cholesterol-nucleation time was studied by mixing the vesicle solution with artificial supersaturated bile. A potent cholesterol-pronucleating activity, reflected in a 20-70% reduction in nucleation time, was present in the biliary vesicle solutions compared with control solutions having a similar lipid composition. The pronucleating activity disappeared on heating and was not detected in the micellar fraction containing the major proportion of biliary proteins. 3. These results indicate that cholesterol-rich biliary vesicles containing a unique and defined glycoprotein profile can be isolated and purified from human hepatic bile. The potent cholesterol-pronucleating activity of the biliary vesicles from patients with gallstones was unrelated to their lipid composition or cholesterol content.(ABSTRACT TRUNCATED AT 250 WORDS) |
| Isolation and quantification of cholesterol oxides in dairy products by selected ion monitoring mass spectrometry Nielsen, J. H., C. E. Olsen, et al. (1995), J Dairy Res 62(1): 101-13. Abstract: A method for isolation, detection and quantification of cholesterol oxidation products based on solid phase extraction in combination with preparative HPLC and gas chromatography-mass spectrometry selected ion monitoring has been developed for dairy products. The isolation procedure had a high recovery and artifact formation was minimal, as shown by isotope labelling. The limits of detection ranged from 0.3 to 35 pg/microliters of the isomeric forms of 7-hydroxycholesterol, 20 alpha-hydroxycholesterol, the isomeric forms of cholesterol-5,6-epoxides, cholestanetriol, 25-hydroxycholesterol and 7-ketocholesterol corresponding to a limit of quantification of 2-6 ng oxysterol/g lipid in the dairy product, depending on the nature of the cholesterol oxidation product. |
| Isolation of a calcium-regulatory protein from black pigment gallstones: similarity with a protein from cholesterol gallstones Okido, M., S. Shimizu, et al. (1992), Hepatology 15(6): 1079-85. Abstract: We have previously isolated from 13 cholesterol gallstones a low molecular weight acidic bili-protein that inhibited the precipitation of calcium carbonate in vitro. We now report the isolation of a similar protein from seven black pigment gallstones. Cholesterol was removed from the stones by Soxhlet apparatus with methyl t-butyl ether, and bile acids were extracted with methanol. The protein was purified by sodium dodecyl sulfate-polyacrylamide gel electrophoresis after demineralization of the stones with ethylenediaminetetraacetate. Structural and functional properties of the protein from the black stones that were similar to the protein from the cholesterol stones included the following: (a) an apparent molecular weight of about 5 kD; (b) a high content of acidic (19.8%) and hydrophobic (50.1%) amino acids with a low content of basic residues (8.4%) and little sulfide-containing amino acids (1.9%); (c) an inhibitory effect on both the initiation and growth of calcium carbonate crystals in vitro; and (d) very tight (possibly covalent) binding of a diazo-positive yellow pigment, presumably bilirubin, with maximum spectral absorbance at 410 nm. The structural and functional similarities of these bili-proteins from black pigment and cholesterol gallstones and their striking effects on calcium carbonate precipitation in vitro suggest that they play a common role in the regulation of precipitation of calcium salts during the formation of both types of gallstones. |
| Isolation of a candidate gene, CAB1, for cholesterol transport to mitochondria from the c-ERBB-2 amplicon by a modified cDNA selection method Akiyama, N., H. Sasaki, et al. (1997), Cancer Res 57(16): 3548-53. Abstract: An improved cDNA selection method was established to isolate expressed genes efficiently from an amplified chromosome region in human cancer. Biotinylated yeast artificial chromosome DNA containing c-ERBB-2 was hybridized in solution with PCR-amplifiable cDNAs of an esophageal cancer cell line bearing the c-ERBB-2 amplification. After capturing the hybrids on avidin-coated magnetic beads, the cDNAs were amplified by PCR. Four new genes (A39, C51, CAB1, and GRB-7) coamplified with c-ERBB-2 were isolated from the enriched cDNA library. CAB1, GRB-7, and c-ERBB-2 were overexpressed in gastric and esophageal cancer cells in correspondence with the amplification. The deduced amino acid sequence of the CAB1 gene had significant homology to the recently discovered steroidogenic acute regulatory protein, StAR, which plays an essential role in cholesterol transport to mitochondria. It was established that multiple overexpressed genes are frequently present in a single amplicon. |
| Isolation of a delta7-cholesterol desaturase from Tetrahymena thermophila Valcarce, G., J. Florin-Christensen, et al. (2000), Appl Microbiol Biotechnol 53(5): 591-5. Abstract: Cell-free preparations of Tetrahymena thermophila catalyze the direct desaturation of cholesterol to delta7-dehydrocholesterol (provitamin D3). The activity was isolated in the microsomal fraction from Tetrahymena homogenates. Delta7-desaturase activity was stimulated fivefold by the addition of 6 mM ATP. Other cofactors assayed, including NAD, NADP, NADH or NADPH, had no significant effect. The activity was found in microsomes prepared from stationary-phase cultures of the ciliate, grown either with or without added cholesterol, thus indicating that it is constitutively expressed in T. thermophila cells. |