| For medical practitioners and the general public - Cholesterol Journal Article Catalog. |
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| Measurement of serum low density lipoprotein-cholesterol in patients with hypertriglycemia Horiuchi, Y., K. Takanohashi, et al. (2000), Electrophoresis 21(2): 293-6. Abstract: Low density lipoprotein-cholesterol (LDL-c) concentration measured by a homogeneous enzymatic assay was reported to correlate well with the modified beta-quantification assay, especially in samples with high triglyceride (TG) concentration. In this study, we evaluated a homogeneous enzymatic assay, Cholestest-LDL assay system, in hypertriglycemic patient samples, and found that 56% (9/16) of serum samples with intermediate TG concentrations (2.27-4.52 mmol/L) showed more than 10% discrepancy with concentration by the modified beta-quantification assay. Such serum samples originated from patients with hyperglycemia of type II a (three cases), type II b (two cases), type III (one case), and type IV (six cases). Differential staining of cholesterol and triglyceride after agarose gel electrophoresis revealed that these serum samples contained significant amounts of intermediate fractions between pre-beta- and beta-lipoproteins. Since lipoprotein (a), which migrates between pre-beta- and beta-lipoproteins, is not correlated with the discrepancy, we believe the intermediate fraction consists of intermediate density lipoprotein (IDL) and a chylomicron remnant. A part of IDL and chylomicron remnant, which contain a significant amount of triglyceride, might be measured as LDL-c by the homogeneous enzymatic assay, but not by the modified beta-quantification assay. |
| Measurements of cholesterol in a department store--a publicity generating groundless anxiety Hakansson, J. (1999), Lakartidningen 96(12): 1426-7. |
| Measurements of serum LDL cholesterol--uncertainty and sources of errors Kallner, A. (2004), Lakartidningen 101(13): 1199-201. Abstract: LDL cholesterol concentrations are still routinely estimated from results of cholesterol, triglycerides and HDL-cholesterol measurements. Deficiencies in this approach are discussed and sources of uncertainty in the estimation highlighted. It is concluded that random variation in the estimated LDL is less than the systematic deviation in the target concentration interval for statin treatment and that an increased use of apolipoprotein measurements would enhance diagnosis and treatment of hyperlipemia. |
| Measuring and knowing. The trouble with cholesterol and decision making Gwynne, J. T. (1991), Jama 266(12): 1696-8. |
| Measuring behaviour in children with high cholesterol levels Joyce, D. P. and M. M. Limbos (1997), Cmaj 157(4): 372-3. |
| Measuring blood cholesterol Hailey, D. M., A. R. Lea, et al. (1991), Aust J Public Health 15(4): 310-1. |
| Measuring blood cholesterol outside the pathology laboratory: issues of accuracy and reliability Reid, C. M., G. L. Jennings, et al. (1991), Aust J Public Health 15(2): 142-6. Abstract: Desk-top analysers that are simple to use, portable and free from technical requirements are now widely used for blood cholesterol measurement outside the traditional pathology laboratory setting. Test accuracy and reliability are essential if these portable desk-top analysers are to be of value in the assessment and management of elevated blood cholesterol. To determine their accuracy and reliability we compared the results obtained from four different desk-top analysers with those from a teaching hospital's routine laboratory method. The desk-top analysers assessed were the Ames Minilab, the Kodak DT60, the Boehringer Reflotron and the Abbott Vision. The precision of each desk-top analyser was within acceptable limits, defined as a coefficient of variation less than 5 per cent. The results from the Vision, Reflotron and DT60 related closely to those from routine laboratory method, with least squares linear regression slopes ranging from 0.92 to 1.06 and intra-class correlation coefficients from 0.95 to 0.99. The Minilab showed least agreement with the routine laboratory method and caution should be taken in the interpretation of cholesterol estimations made with this device. |
| Measuring cholesterol in macrophages: comparison of high-performance liquid chromatography and gas-liquid chromatography with enzymatic fluorometry Cullen, P., K. Tegelkamp, et al. (1997), Anal Biochem 251(1): 39-44. Abstract: Cholesterol and cholesteryl esters in human macrophages were analyzed by three different methods. Values obtained by high-performance liquid chromatography and by gas-liquid chromatography were compared with those obtained using enzymatic fluorometry. We also assessed fractional lipid recovery from these cells using radiolabeled cholesterol and cholesteryl ester. Enzymatic fluorometry substantially underestimated cellular cholesterol content. Two reasons for this were found. First, recovery into a variety of solvents was incomplete, particularly when extracted lipids were dried and redissolved in a second solvent. Second, the cells appeared to contain an intrinsic inhibitor of the enzymatic fluorometric method. |
| Measuring cholesterol without interference from lipemia Poon, R., I. Hinberg, et al. (1990), Clin Chem 36(12): 2149-50. |
| Measuring cholesterol. A handbook for out-patient clinics and laboratory personnel Nilsson-Ehle, P. (1990), Ups J Med Sci 95(3): 279-85. |
| Measuring lipogenesis and cholesterol synthesis in humans with deuterated water: use of simple gas chromatographic/mass spectrometric techniques Diraison, F., C. Pachiaudi, et al. (1997), J Mass Spectrom 32(1): 81-6. Abstract: Lipogenesis and cholesterol synthesis can be studied by measuring the incorporation into fatty acids and cholesterol of deuterium from deuterated water. This has been previously achieved in human subjects using low levels of deuterium enrichment in plasma water, and thus in fatty acids and cholesterol. For the measurement of enrichment in lipids, this required the use of isotope ratio mass spectrometry, a tedious and time-consuming technique. It is shown that these measurements can be performed using the much simpler gas chromatography/mass spectrometry if higher, but always safe, deuterium enrichments in plasma water are obtained. Normal subjects ingested deuterated water in order to obtain stable enrichment in plasma water of 0.3% during a 60 h period. Enrichment in palmitate of plasma triglycerides (TG) plateaued (0.6-0.76%) whereas plasma cholesterol enrichment increased progressively 0.32 +/- 0.08% (12 h) to 0.78 +/- 0.18% (60 h). Endogenous synthesis was estimated to contribute, in post-absorptive subjects, 8-10% of the plasma TG pool and 3-5% of plasma free cholesterol pool. These data agree with results obtained previously using isotope ratio mass spectrometry. The present method will be useful for studies of normal and abnormal lipid metabolism in humans. |
| Measuring serum total cholesterol: do vascular surgeons know what they are doing? Wijesinghe, L. D., L. Gamage, et al. (1999), Ann R Coll Surg Engl 81(1): 32-6. Abstract: Raised serum total cholesterol (TC) is an accepted risk factor for both coronary and peripheral vascular disease and three landmark trials have shown the benefit of lowering TC using statins. Vascular surgeons tend to measure TC, but little is known about how they manage hypercholesterolaemia or whether they believe treatment will be of benefit. A questionnaire was sent to listed members of the Vascular Surgical Society of Great Britain and Ireland seeking responses to a range of questions on the measurement and management of raised TC. In all, 374 questionnaires were sent out. The response rate was 67%. Over 90% of respondents said they measured TC and considered a level below 5.5 mmol/l as normal. The cut-off for initiating drug therapy, referral to a dietician or to a lipid specialist varied from 5.5 to 7.5 mmol/l. Most (62%) believed that lowering TC improved coronary mortality, but fewer (26%) that it prevented worsening of claudication. Although most vascular surgeons check for raised TC, the level at which treatment begins and the form it takes varies; in many cases being at odds with recommendations. Few surgeons are convinced of the benefits of lowering TC for claudication and nearly one-fifth do not believe it improves coronary mortality. |
| Meat consumption and serum cholesterol concentration Bodenmann, A., U. Ackermann-Liebrich, et al. (1991), Dtsch Med Wochenschr 116(28-29): 1089-94. Abstract: In a representative cross-sectional study of the population of Basel, Switzerland (252 men, 281 women, mean age 48 25-74 years), there was a significant association between the consumption of meat and sausages, determined from a questionnaire, and the total serum cholesterol concentration. In subjects who ate meat or sausages daily, the mean cholesterol concentration was 6.29 mmol/l (242 mg/dl) (95% confidence interval 6.06-6.52 mmol/l) for men, and 6.63 mmol/l (255 mg/dl) (95% confidence interval 6.35-6.91 mmol/l) for women. In subjects who consumed meat or sausages at most once per week, the mean cholesterol concentration was 5.66 mmol/l (218 mg/dl) (95% confidence interval 4.99-6.33 mmol/l) for men, and 5.33 mmol/l (205 mg/dl) (95% confidence interval 4.98-5.68 mmol/l) for women. The association remained significant (P less than 0.001) using multiple linear regression (taking age, sex, social grouping, body mass index and consumption of whole-grain bread, yoghurt or cottage cheese, eggs and alcohol as possible confounding factors). The HDL-cholesterol fraction was not influenced by consumption of meat and sausages. These results support the nutritional advice concerning, among other things, a reduction in the intake of animal fats. |
| Mechanism for the transit-induced increase in colonic deoxycholic acid formation in cholesterol cholelithiasis Thomas, L. A., M. J. Veysey, et al. (2000), Gastroenterology 119(3): 806-15. Abstract: BACKGROUND & AIMS: Many patients with cholesterol gallbladder stones (GBS) have a high percentage of deoxycholic acid (DCA) in gallbladder bile (all of which are in the conjugated form), probably as a result of prolonged large bowel transit times (LBTT). However, whether the prolonged LBTT increases DCA formation, solubilization, or absorption (or all 3) is not known. METHODS: In 40 subjects (20 with GBS; age range, 24-74 years), we measured LBTT using radiopaque markers, and intestinal luminal pH by radiotelemetry. We also measured quantitative anaerobic bacteriology and the activities of 2 bile acid-metabolizing enzymes in fresh cecal aspirates obtained during clinically indicated unprepared colonoscopy, and related these results to the percentage of DCA in fasting serum measured by gas chromatography-mass spectrometry. RESULTS: Compared with controls, GBS patients had longer LBTT (mean 23.1 +/- SEM 2.8 h vs. 36.5 +/- 3.3 h; P < 0.01); more total (2.7 +/- 0.6 x 10(9) vs. 5.9 +/- 1.5 x 10(9) cfu/mL) and Gram-positive (9.5 +/- 3.1 x 10(8) vs. 18.0 +/- 4.1 x 10(8) cfu/mL; P < 0.05) anaerobes; and greater 7alpha-dehydroxylating (7alpha-DH) activity (3.39 +/- 0.59 vs. 10.37 +/- 1.15 x 10(-4) U/mg protein) in the cecal aspirates. They also had higher intracolonic pH values (P < 0.02) and increased percentages of DCA in fasting serum (13.4% +/- 1.52% vs. 21.8% +/- 2. 19%; P < 0.005). Results of univariate and multivariate analyses confirmed that LBTT was critical in determining the percentage of DCA in serum and showed that 7alpha-DH activity and apparent distal colonic pH were also significant independent variables. CONCLUSIONS: Slow colonic transit (more time), increased Gram-positive anaerobes (more bacteria), and greater 7alpha-DH activity (more enzyme) favor enhanced DCA formation; transit-induced increases in distal colonic luminal pH favor enhanced DCA solubilization/bioavailability; and increases in LBTT (more time) again favor DCA absorption. |
| Mechanism of accumulation of cholesterol and cholestanol in tendons and the role of sterol 27-hydroxylase (CYP27A1) von Bahr, S., T. Movin, et al. (2002), Arterioscler Thromb Vasc Biol 22(7): 1129-35. Abstract: OBJECTIVE: Tendon xanthomas are deposits of lipids and connective tissue commonly found in hypercholesterolemic patients. Macrophages are likely to be responsible for the lipid accumulation. Normolipidemic patients with the rare disease cerebrotendinous xanthomatosis, lacking the enzyme sterol 27-hydroxylase (CYP27A1), develop prominent xanthomas in tendons and brain containing both cholestanol and cholesterol, with a cholestanol:cholesterol ratio higher than that in the circulation. Because of its ability to convert cholesterol into polar metabolites that leave the cells faster, CYP27A1 has been suggested to be an antiatherogenic enzyme. The hypothesis was tested that tendons contain CYP27A1 that may be of importance for the normal efflux of both steroids. METHODS AND RESULTS: Western blotting and combined gas chromatography-mass spectrometry showed that human tendons contain significant amounts of CYP27A1 and its product, 27-hydroxycholesterol. Immunohistochemistry showed that CYP27A1 is present in macrophages and tenocytes. The tendons also contained cholestanol, with a cholestanol:cholesterol ratio slightly higher than that in the circulation. Recombinant human CYP27A1, and cultured human macrophages containing this enzyme, had similar activity toward cholesterol and cholestanol. After loading of macrophages with labeled cholesterol and cholestanol, there was an efflux of these steroids in both unmetabolized and 27-oxygenated form, resulting in a significant cellular accumulation of cholestanol compared with cholesterol. CONCLUSION: The results are consistent with the possibility that CYP27A1 is of importance for the efflux of both cholesterol and cholestanol from tendons. |
| Mechanism of action of sterol regulatory element binding proteins (SREBPs) in cholesterol and fatty-acid biosynthesis Manzano Leon, N., N. Torres, et al. (2002), Rev Invest Clin 54(2): 145-53. Abstract: Cholesterol is an important lipid in higher organisms, and its concentration must be maintained in narrow limits depending of the cell needs. An excess of dietary cholesterol can lead to serious health problems, however, if consumption of this lipid is restricted in the diet, cells have the capacity to synthesize it. For the synthesis of cholesterol, the cell uses a family of proteins named sterol regulatory element binding proteins (SREBP's), that are transcriptional factors involved in the control of expression of genes of cholesterol and fatty acids synthesis. SREBP's regulate gene transcription by binding to cis-acting elements denominated sterol regulatory elements (SRE-1). SREBP's are localized in the endoplasmic reticulum, but in the event that the cell needs to synthesize cholesterol, the NH2-terminal portion of these proteins is cleaved by two specific proteases, and then travels into the nucleus to function as transcriptional factor. The present review shows the details of the mechanism that the cell uses to regulate cholesterol biosynthesis by the SREBP's, and its potential metabolic implications. |
| Mechanism of cellular cholesterol removal: a communication system between extracellular cholesterol transport and intracellular cholesterol homeostasis Yokoyama, S. (1998), Nippon Yakurigaku Zasshi 111(2): 77-85. Abstract: Cholesterol efflux is one of the essential events in cellular cholesterol homeostasis since peripheral cells do not catabolize the cholesterol molecule. There are two distinct mechanisms for the efflux. One is the non-specific classical pathway mediated by physicochemical diffusion of cholesterol through the aqueous phase and its esterification on high density lipoprotein (HDL) by lecithin: cholesterol acyltransferase (LCAT). The other is the specific and biological pathway in which new HDL particles are generated from cellular lipid by the direct interaction of cell membrane and amphiphilic apolipoproteins that have dissociated from HDL. The latter reaction consists of binding of apolipoprotein to the specific binding site of the cellular surface and subsequent mobilization of intracellular cholesterol for the HDL generation mediated by intracellular signal transduction. This reaction seems to be a major source of plasma HDL. |
| Mechanism of cholesterol reduction to coprostanol by Eubacterium coprostanoligenes ATCC 51222 Ren, D., L. Li, et al. (1996), Steroids 61(1): 33-40. Abstract: The mechanism of reduction of cholesterol to coprostanol by Eubacterium coprostanoligenes ATCC 51222 was studied by incubating the bacterium with a mixture of alpha- and beta-isomers of 4-3H,4-14Ccholesterol. Coprostanol, isolated after incubation of 4-3H,4-14Ccholesterol in a growth medium under anaerobic conditions, retained 97% of the tritium originally present in cholesterol. The majority of this tritium (64%), however, was in the C-6 position in coprostanol, which showed that the conversion of cholesterol into coprostanol by E. coprostanoligenes involved the intermediate formation of 4-cholesten-3-one followed by the reduction of the latter to coprostanol. In resting cell assays in which washed bacterial cells were incubated with micellar cholesterol in phosphate buffer at 37 degrees C, both 4-cholesten-3-one and coprostanone were produced in addition to coprostanol. Furthermore, 5-cholesten-3-one, 4-cholesten-3-one, and coprostanone were converted efficiently to coprostanol by E. coprostanoligenes. These results support the hypothesis that the major pathway for reduction of cholesterol by E. coprostanoligenes involves the intermediate formation of 4-cholesten-3-one followed by reduction of the latter to coprostanol through coprostanone as an intermediate. |
| Mechanism of hypocholesterolemic effect of oyster mushroom (Pleurotus ostreatus) in rats: reduction of cholesterol absorption and increase of plasma cholesterol removal Bobek, P., L. Ozdin, et al. (1994), Z Ernahrungswiss 33(1): 44-50. Abstract: The content of cholesterol in the serum and liver of male Wistar rats fed, for the period of 8 weeks shortly after weaning, a diet containing 0.3% of cholesterol was reduced by 33 and 27% by the addition of 5% of dried oyster mushroom powder. Although the level of serum triacylglycerols was not affected by oyster mushroom, their content in liver of rats on mushroom diet was reduced by 41%. Very-low-density lipoproteins and low-density lipoproteins participated by 55 and 38%, respectively, in the total reduction of serum cholesterol. Cholesterol content in high-density lipoproteins was not significantly affected by oyster mushroom. Cholesterol absorption as determined by dual-isotope plasma ratio method was significantly reduced by 14% with oyster mushroom diet. Similarly, this diet increased by 42% the fractional catabolic rate of cholesterol determined by the analysis of decay curve of 4-14Ccholesterol. |
| Mechanism of inhibition of lipid peroxidation by tamoxifen and 4-hydroxytamoxifen introduced into liposomes. Similarity to cholesterol and ergosterol Wiseman, H., M. Cannon, et al. (1990), FEBS Lett 274(1-2): 107-10. Abstract: The anticancer drug tamoxifen when introduced into phospholipid liposomes during their preparation inhibited Fe(III)-ascorbate induced lipid peroxidation to a greater extent than similarly introduced cholesterol. Ergosterol was equipotent with tamoxifen, but much less effective than 4-hydroxytamoxifen. Possible mechanisms underlying these effects are discussed in relation to structural mimicry of the sterols by these triphenylethylene drugs as membrane stabilizers against lipid peroxidation. |