| For medical practitioners and the general public - Cholesterol Journal Article Catalog. |
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| Compared with Acyl-CoA:cholesterol O-acyltransferase (ACAT) 1 and lecithin:cholesterol acyltransferase, ACAT2 displays the greatest capacity to differentiate cholesterol from sitosterol Temel, R. E., A. K. Gebre, et al. (2003), J Biol Chem 278(48): 47594-601. Abstract: The capacity of acyl-CoA:cholesterol O-acyltransferase (ACAT) 2 to differentiate cholesterol from the plant sterol, sitosterol, was compared with that of the sterol esterifying enzymes, ACAT1 and lecithin:cholesterol acyltransferase (LCAT). Cholesterol-loaded microsomes from transfected cells containing either ACAT1 or ACAT2 exhibited significantly more ACAT activity than their sitosterol-loaded counterparts. In sitosterol-loaded microsomes, both ACAT1 and ACAT2 were able to esterify sitosterol albeit with lower efficiencies than cholesterol. The mass ratios of cholesterol ester to sitosterol ester formed by ACAT1 and ACAT2 were 1.6 and 7.2, respectively. Compared with ACAT1, ACAT2 selectively esterified cholesterol even when sitosterol was loaded into the microsomes. To further characterize the difference in sterol specificity, ACAT1 and ACAT2 were compared in intact cells loaded with either cholesterol or sitosterol. Despite a lower level of ACAT activity, the ACAT1-expressing cells esterified 4-fold more sitosterol than the ACAT2 cells. The data showed that compared with ACAT1, ACAT2 displayed significantly greater selectively for cholesterol compared with sitosterol. The plasma cholesterol esterification enzyme lecithin:cholesterol acyltransferase was also compared. With recombinant high density lipoprotein particles, the esterification rate of cholesterol by LCAT was only 15% greater than for sitosterol. Thus, LCAT was able to efficiently esterify both cholesterol and sitosterol. In contrast, ACAT2 demonstrated a strong preference for cholesterol rather than sitosterol. This sterol selectivity by ACAT2 may reflect a role in the sorting of dietary sterols during their absorption by the intestine in vivo. |
| Compared with saturated fatty acids, dietary monounsaturated fatty acids and carbohydrates increase atherosclerosis and VLDL cholesterol levels in LDL receptor-deficient, but not apolipoprotein E-deficient, mice Merkel, M., W. Velez-Carrasco, et al. (2001), Proc Natl Acad Sci U S A 98(23): 13294-9. Abstract: Heart-healthy dietary recommendations include decreasing the intake of saturated fatty acids (SFA). However, the relative benefit of replacing SFA with monounsaturated fatty acids (MUFA), polyunsaturated fatty acids (PUFA), or carbohydrates (CARB) is still being debated. We have used two mouse models of atherosclerosis, low density lipoprotein receptor-deficient (LDLRKO) and apolipoprotein E-deficient (apoEKO) mice to measure the effects of four isocaloric diets enriched with either SFA, MUFA, PUFA, or CARB on atherosclerotic lesion area and lipoprotein levels. In LDLRKO mice, compared with the SFA diet, the MUFA and CARB diets significantly increased atherosclerosis in both sexes, but the PUFA diet had no effect. The MUFA and CARB diets also increased very low density lipoprotein-cholesterol (VLDL-C) and LDL-cholesterol (LDL-C) in males and VLDL-C levels in females. Analysis of data from LDLRKO mice on all diets showed that atherosclerotic lesion area correlated positively with VLDL-C levels (males: r = 0.47, P < 0.005; females: r = 0.52, P < 0.001). In contrast, in apoEKO mice there were no significant dietary effects on atherosclerosis in either sex. Compared with the SFA diet, the CARB diet significantly decreased VLDL-C in males and the MUFA, PUFA, and CARB diets decreased VLDL-C and the CARB diet decreased LDL-C in females. In summary, in LDLRKO mice the replacement of dietary SFA by either MUFA or CARB causes a proportionate increase in both atherosclerotic lesion area and VLDL-C. There were no significant dietary effects on atherosclerotic lesion area in apoEKO mice. These results are surprising and suggest that, depending on the underlying genotype, dietary MUFA and CARB can actually increase atherosclerosis susceptibility, probably by raising VLDL-C levels through a non-LDL receptor, apoE-dependent pathway. |
| Comparing physical activity assessment methods in the Seasonal Variation of Blood Cholesterol Study Matthews, C. E., P. S. Freedson, et al. (2000), Med Sci Sports Exerc 32(5): 976-84. Abstract: PURPOSE: This paper evaluated three measures of physical activity employed in the Seasonal Variation of Blood Cholesterol Study (Seasons), and it had two objectives: 1) To examine the laboratory validity of the Actillume activity monitor, and 2) To examine the relative validity of three 24-h physical activity recalls (24HR) in quantifying short-term physical activity behaviors. METHODS: Nineteen healthy middle-age adults completed seven activity trials (reading, typing, box moving, stepping, and walking (3.5, 4.25, 5.0 km x h(-1))) while oxygen consumption and Actillume measures were obtained. ANOVA, linear regression, and a scatter plot were employed to examine the validity of the Actillume. In relative validity analyses of the 24HR in the Seasons study, participants (N = 481) completed two or three 24HR (MET-h x d(-1)) and a modified Baecke Questionnaire. A subset of the cohort (N = 41) wore the Actillume for 3-8 d (counts x min(-1) x d(-1)). The relative validity of the 24HR method was examined by comparison to these criterion measures. RESULTS: In laboratory validation analyses, the monitor was found to discriminate between sedentary and moderate intensity activities, changes in walking speed, and to account for 79% of the variance in oxygen consumption across sedentary and walking trials. In relative validity analyses, correlations between the 24HR and the modified Baecke ranged from 0.29 to 0.52 (P < 0.01) across total, household, occupational, and leisure-time activities. CONCLUSIONS: In laboratory testing, the Actillume monitor discriminated between sedentary and moderate intensity activities and was highly correlated with oxygen consumption. Three 24HR of physical activity were observed to have a relative validity that was comparable to published data from other short-term activity assessments that also employed the Baecke Questionnaire and activity monitors as criterion measures. |
| Comparing the efficacy and safety of atorvastatin and simvastatin in Asians with elevated low-density lipoprotein-cholesterol--a multinational, multicenter, double-blind study Wu, C. C., R. Sy, et al. (2002), J Formos Med Assoc 101(7): 478-87. Abstract: BACKGROUND AND PURPOSE: There have been few reports on the efficacy and safety of statins in the Asian population. The study objectives were to compare the efficacy and safety of atorvastatin and simvastatin in Asian people. MATERIALS AND METHODS: This was a 16-week, double-blind, double-dummy, randomized, multicenter study involving eight medical centers in six Asian countries or areas. After a 6-week, diet-controlled, placebo lead-in period, 157 patients with low-density lipoprotein cholesterol (LDL-C) of between 160 and 250 mg/dL and serum triglyceride (TG) of less than 400 mg/dL were randomized to receive 10 mg of either atorvastatin (n = 79) or simvastatin (n = 78). After 8 weeks of treatment, all patients had the dose of study medication increased to 20 mg, irrespective of LDL-C concentration. Data obtained by monitoring lipid profiles, adverse events, and laboratory tests during the 16 weeks of study were used to assess the efficacy and safety of both treatments. RESULTS: After 8 weeks of treatment, LDL-C concentrations were reduced by 42.5% from baseline in patients receiving atorvastatin and 34.8% in those receiving simvastatin (p = 0.0006). Patients treated with atorvastatin also had a significantly greater reduction in very-low-density lipoprotein cholesterol (VLDL-C), TG, and total cholesterol (TC) after 8 weeks of treatment. The significantly greater reductions in LDL-C, VLDL-C, TG, and TC from baseline achieved with atorvastatin were still observed after an additional 8 weeks of treatment with 20 mg study medication. Both drugs increased high-density lipoprotein cholesterol (HDL-C) concentrations after 16 weeks of treatment, with no significant difference between the two treatments. After 16 weeks of treatment, 93% of atorvastatin and 85% of simvastatin patients had achieved their National Cholesterol Education Program LDL-C goals. No deaths occurred in the study population and the incidence of treatment-emergent adverse events was the same in the two groups (28%). Only one patient who was treated with simvastatin had a transaminase or creatine phosphokinase concentration that was more than three-fold the upper limit of normal. CONCLUSIONS: Asian people with primary hypercholesterolemia treated with atorvastatin had lower LDL-C, VLDL-C, TG, and TC after 8 weeks and 16 weeks of treatment than those treated with simvastatin. Both drugs demonstrated acceptable safety profiles. |
| Comparing the results of a cholesterol and saturated fat screener when using two different scores Rohrmann, S. and G. Klein (2003), Eur J Epidemiol 18(5): 413-5. Abstract: Screener are useful instruments for categorising individuals according to their nutrient intake. To accurately classify the individuals it is important to correctly analyse the screener. Therefore we compared a simple and a weighed score of a cholesterol and saturated fat (SF) screener with the cholesterol and SF intake, respectively, calculated from an extensive food frequency questionnaire. The validation results did not change when a weighed score was used instead of the simple one, indicating that a simple score does not introduce a higher amount of misclassification. |
| Comparing two strategies to modify dietary behavior and serum cholesterol Reynolds, K. D., J. L. Gillum, et al. (1997), J Cardiovasc Risk 4(1): 1-5. Abstract: AIM: To test the hypothesis that a strategy including cholesterol screening and dietary education is more effective than dietary education alone in changing dietary behavior and serum cholesterol levels. METHODS: Individuals at four worksites were enrolled in a randomized trial with a 'full intervention' condition in which subjects were told their serum cholesterol value and also received a dietary change kit (n = 236), and a 'partial intervention' condition in which subjects received the same dietary change kit, but were not told their serum cholesterol value (n = 284). Individuals (n = 115) in two worksites served as a nonrandomized 'untreated control group'. Subjects were tested for serum cholesterol and completed a questionnaire at baseline, and 3 and 6 months later. RESULTS: Dietary changes occurred in seven of nine categories in individuals subjects to the full and partial interventions but in only one of nine categories in those studied in the control condition. Mean dietary intake differed between the full and partial intervention conditions for only three of nine dietary categories. Cholesterol level dropped in the full, partial and control conditions by 4.9, 3.9 and 9.6%, respectively. CONCLUSIONS: Dietary education has favorable effects on the dietary behaviors of individuals. Being told one's cholesterol level at the outset of this educational intervention has little effect on dietary change. |
| Comparison between HDL and LDL cholesterol as risk factors for carotid atherosclerosis Gagliardi, R. J., M. Sanches, et al. (1995), Arq Neuropsiquiatr 53(4): 730-6. Abstract: In order to find out whether there exists a relationship between HDL and LDL serum levels and atherosclerotic plaques in the carotid artery (CA), a prospective study was carried out involving 125 patients. They were aleatorily included, of both sexes and age between 45-75 years old. HDL and LDL serum levels were measured as well CA ultrasonographic mode B investigated. It was verified that the number of patients having atherosclerotic plaques in CA was inversely proportional to the HDL levels. We came up with the same ratio when the HDL levels were compared to the number of patients having CA stenosis. These results were statistically significant (x2 = 6.57 and x2 = 9.24 respectively; critical x2 = 5.99 to alpha = 5%). A direct ratio was also found out in the relationship between the presence of atherosclerotic plaques in the CA and the LDL serum levels (greater in patients with plaques). However no relationship between LDL levels and the occurrence or not of CA stenosis in patients having plaques was demonstrated. The results were not statistically significant (x2 = 0.97 and x2 = 0.41, respectively, critical x2 = 5.99 to alpha = 5%). The obtained results seem to be at least in part in agreement with literature findings. Statistically significative results in the comparison of HDL and LDL levels with the grade of stenosis of the CA were not found out (x2 = 11.78 and x2 = 4.03, respectively; critical x2 = 12.59 to alpha = 5%). |
| Comparison between the effects of dietary saturated (16:0), monounsaturated (18:1), and polyunsaturated (18:2) fatty acids on plasma lipoprotein metabolism in cebus and rhesus monkeys fed cholesterol-free diets Khosla, P. and K. C. Hayes (1992), Am J Clin Nutr 55(1): 51-62. Abstract: Cebus and rhesus monkeys were fed cholesterol-free diets providing 40% of energy as fat for 6-wk periods. The fats were high-linoleic acid safflower oil (HLSO), high-oleic acid safflower oil (HOSO), or palm oil (PO), rich in polyunsaturated (18:2), monounsaturated (18:1), or saturated (16:0) fatty acids, respectively. In cebus monkeys, plasma cholesterol concentrations during HLSO intake were 17-19% lower than those during HOSO or PO intake, attributed to a decrease in high-density lipoprotein (HDL). Plasma triglyceride (TG) and low-density-lipoprotein (LDL) cholesterol concentrations were comparable during all dietary treatments. Sixty-eight percent of total LDL catabolism was receptor mediated in all dietary groups and this was associated with similar apolipoprotein B pool sizes and fractional catabolic rates. Rhesus monkeys revealed similar cholesterol concentrations (total, LDL, and HDL) during all dietary treatments. TG concentrations during PO intake were 34% and 63% higher than those during HOSO and HLSO intakes, respectively. Hence, dietary 16:0 and 18:1 produce similar effects on LDL and HDL metabolism in normocholesterolemic primates. |
| Comparison between wheat, triticale, rye, soyabean oil and strain of laying bird on the production, and cholesterol and fatty acid contents of eggs Shafey, T. M., J. G. Dingle, et al. (1992), Br Poult Sci 33(2): 339-46. Abstract: 1. The effects of feeding three types of cereal grain (wheat, triticale or rye) and soyabean oil (0 or 20 g/kg) over a 12-week period on the production, yolk cholesterol and yolk fatty acid concentrations of three strains of laying pullets were studied. 2. Pullets fed on wheat- or triticale-based diets had higher body weight gains, egg productions, egg weights, egg mass and lower yolk cholesterol concentrations than pullets fed on rye-based diets. However, there were no significant differences between the cereals in yolk cholesterol content. 3. There were no significant differences between the three cereals in total food consumption of pullets nor of yolk weight nor yolk concentration of palmitic, stearic and oleic acids. 4. Pullets fed on triticale-based diets had higher yolk linoleic acid concentrations and lower yolk oleic acid: linoleic acid ratios than pullets fed on rye- or wheat-based diets. 5. Soyabean oil supplementation increased egg production, egg mass, yolk linoleic concentration and yolk unsaturated to saturated fatty acid ratio, but reduced yolk oleic acid: linoleic acid ratio. 6. There were differences between strains of pullets in weight gain, food consumption, rate of lay, egg weight and yolk cholesterol, but not in yolk fatty acid concentrations. 7. It was concluded that wheat- or triticale-based diets gave good production of eggs of lower cholesterol content, that soyabean oil supplementation gave eggs with a high unsaturated to saturated fatty acid ratio and that two strains of layers produced eggs with lower yolk cholesterol concentrations than a third strain. |
| Comparison of 2 cholesterol synthesis inhibitors (simvastatin and pravastatin) Golay, A., T. Lehmann, et al. (1993), Schweiz Med Wochenschr 123(33): 1553-8. Abstract: Inhibitors of cholesterol synthesis (HMG-CoA reductase) are the most effective cholesterol-lowering drugs. Comparison of several studies in the literature suggests that simvastatin is approximately twice as effective as pravastatin on a milligram basis. These results are confirmed by the present study, which compares treatment with simvastatin (10 mg/d) with pravastatin (20 mg/d) in the same hypercholesterolemic patients (n = 17). The reduction in LDL cholesterol is the same with twice the dose of pravastatin as with simvastatin (26 +/- 3% vs 27 +/- 2% respectively). The reductions in atherogenic ratios, total cholesterol, HDL cholesterol and ApoB/ApoA1 are similar. Undesirable effects are rare and comparable. The differences between the two inhibitors appear to be on the molecular level, in tissue selectively and regarding in vivo efficacy. |
| Comparison of 2 electrophoretic procedures for quantifying lipoprotein cholesterol Kessler, B., J. Aufenanger, et al. (1990), Klin Wochenschr 68 Suppl 22: 110-1. |
| Comparison of 2 homogeneous high-density lipoprotein cholesterol assays Hoang, M. P., S. V. Hirany, et al. (1998), Arch Pathol Lab Med 122(11): 1005-9. Abstract: BACKGROUND: High-density lipoprotein cholesterol (HDL-C) is an independent inverse risk factor for coronary artery disease. Current methodologies for measurement of HDL-C in most clinical laboratories involve chemical precipitation-based methods. However, these methods are time-consuming, affected by high triglycerides, are not suitable for complete automation, and require a large sample size. New direct homogeneous methods are now available that do not have these constraints. DESIGN: We evaluated the performance of 2 direct homogeneous methods, Liquid N-geneous HDL-C assay (LN-HDL) and Boehringer Mannheim HDL Cholesterol assay (BM-HDL), and compared these methods against a modified Centers for Disease Control and Prevention reference method (MR-HDL) in 126 patients with normotriglyceridemia (triglycerides < 4.5 mmol/L, range 0.6-4.3 mmol/ L) and 50 patients with hypertriglyceridemia (triglycerides > or =4.5 mmol/L, range 4.5-18.8 mmol/L). RESULTS: Excellent precision profiles were exhibited by both homogeneous methods. Both LN-HDL and BM-HDL correlated well with MR-HDL in normotriglyceridemia (r = 0.98, slope = 0.93 and r = 0.97, slope = 1.0, respectively). However, compared with the modified reference method, the LN-HDL correlated better than the BM-HDL in hypertriglyceridemic samples (r = 0.97, slope = 1.0 and r = 0.91, slope = 0.9, respectively). The 1998 National Cholesterol Education Program guidelines for accuracy (bias < +/-5%) were met by LN-HDL in both normotriglyceridemic and hypertriglyceridemic samples (bias = 1.3% and 3.3%, respectively); however, BM-HDL failed to meet the National Cholesterol Education Program accuracy criteria in both triglyceride subgroups (bias = 8.2% and 11.3%, respectively). In addition, the total error for LN-HDL in both normotriglyceridemia (6.6%) and hypertriglyceridemia (8.6%) was well within the National Cholesterol Education Program guidelines for total error (< or =13%); BM-HDL exhibited a higher total error than LN-HDL in normotriglyceridemia (11.9%) and failed to meet the National Cholesterol Education Program guidelines in hypertriglyceridemia (15.0%). CONCLUSION: Although both homogeneous methods are precise, the LN-HDL assay is superior in accuracy to the BM-HDL assay when compared with the modified reference method. |
| Comparison of a homogeneous assay with a precipitation method for the measurement of HDL cholesterol in diabetic patients Jensen, T., Q. Truong, et al. (2002), Diabetes Care 25(11): 1914-8. Abstract: OBJECTIVE: To compare direct-measured HDL cholesterol with HDL cholesterol measured by a precipitation method. RESEARCH DESIGN AND METHODS: We compared a homogeneous assay for direct HDL cholesterol analysis with the phosphotungstic acid magnesium chloride precipitation method in 55 type 1 diabetic patients, 70 type 2 diabetic patients, and 82 nondiabetic normal control subjects with plasma triglyceride levels <4.6 mmol/l. The cholesterol content of HDL determined by the direct assay was overall 0.1 mmol/l higher in all three groups than HDL cholesterol measured after precipitation, but the two methods were closely correlated (r(2) = 0.98, P < 0.001). RESULTS: HbA(1c), blood glucose, serum albumin, serum bilirubin, or triglyceride did not influence the differences of the two HDL cholesterol measurements. Because we have previously shown HDL cholesterol isolated by phosphotungstic acid precipitation to be lower than that by ultracentrifugation, the positive bias found in this study was expected. It seems that the direct HDL cholesterol assay reacts with apolipoprotein (apo) B-containing lipoproteins in the fraction with a density of >1.063; these apo B-containing lipoproteins are suggested to be coprecipitated with the phosphotungstic acid method. We also measured LDL cholesterol directly by a LDL cholesterol plus method and found no significant differences between this method and LDL cholesterol calculated from Friedewald's formula. CONCLUSIONS: Direct homogeneous assay for HDL cholesterol determination in diabetic patients seems not to exhibit a negative bias, in contrast to the precipitation method, when compared with the ultracentrifugation method. In addition, the direct assay saves time and is not influenced by type of diabetes or degree of metabolic control. |
| Comparison of a new method for the direct and simultaneous assessment of LDL- and HDL-cholesterol with ultracentrifugation and established methods Benlian, P., C. Cansier, et al. (2000), Clin Chem 46(4): 493-505. Abstract: BACKGROUND: Automated electrophoresis combined with enzymatic cholesterol staining might improve routine assessment of LDL- and HDL-cholesterol (LDLC and HDLC), as an alternative to the Friedewald equation and precipitation. A new method (Hydrasys; SEBIA) that adapts the cholesterol esterase/cholesterol oxidase reaction within urea-free gels was evaluated. METHODS: Fresh sera from 725 subjects (512 dyslipidemics) were analyzed by electrophoresis, in parallel with sequential ultracentrifugation, beta-quantification, calculation, and precipitation. RESULTS: Electrophoresis was linear up to 4 g/L cholesterol, with a detection limit of 0.042 g/L cholesterol/band. Within-run, between-run, between-batch, and between-operator imprecision (CVs) were 1.6%, 2.0%, 1.5%, and 2.7% for LDLC, and 3.9%, 4.3%, 5.5%, and 4.9% for HDLC, and remained unchanged up to 6.3 g/L plasma triglycerides (TGs). Precision decreased with very low HDLC (<0.25 g/L). Serum storage for 3-7 days at +4 or -80 degrees C did not interfere significantly with the assay. Agreement with beta-quantification was stable for LDLC up to 5.07 g/L (r = 0.94), even at TG concentrations >4 g/L (r = 0.91). Bias (2.88% +/- 12%) and total error (7.84%) were unchanged at TG concentrations up to 18.5 g/L. Electrophoresis predicted National Cholesterol Education Program cut-points with <0.04 g/L error, exactly and appropriately classified 79% and 96% of the subjects, and divided by 2.4 (all subjects) and 5.8 (TGs >1.5 g/L) the percentage of subjects underestimated by calculation. One-half of the patients with TGs >4 g/L had LDLC >1.30 g/L. For HDLC, correlation was better with precipitation (r = 0.87) than ultracentrifugation (r = 0.76). Error (-0.10% +/- 26%) increased when HDLC decreased (<0.35 g/L). Direct assessment of the LDLC/HDLC ratio detected 45% more high-risk subjects than the calculation/precipitation combination. CONCLUSIONS: Electrophoresis provides reliable quantification of LDLC, improving precision, accuracy, and concordance over calculation, particularly with increasing plasma TGs. Implementation of methods to detect low cholesterol concentrations could extend the applications for HDLC assessment. |
| Comparison of an immunoprecipitation method for direct measurement of LDL-cholesterol with beta-quantification (ultracentrifugation) Jialal, I., S. V. Hirany, et al. (1995), Am J Clin Pathol 104(1): 76-81. Abstract: A direct LDL cholesterol assay was evaluated using immunoprecipitation (Sigma Diagnostics, St. Louis, MO) with beta-quantification obtained by ultracentrifugation. Excellent intra- and interassay coefficients of variation were obtained (< 4.5%). There was a good correlation (r = 0.88, P <.0001) between the two methods for low-density lipoprotein cholesterol (LDL-C) in 249 samples with triglyceride levels ranging from 13 mg/dL to 2,236 mg/dL and LDL cholesterol levels ranging from 28 mg/dL to 290 mg/dL. Similar correlations were seen for patients with triglyceride levels < 400 mg/dL (r = 0.89, n = 174) and > or = 400 mg/dL (r = 0.89, n = 75). However, using the Friedewald equation, there was a good correlation only in samples with triglyceride levels < 400 mg/dL. No significant differences were found between LDL-C quantitated by the direct LDL assay and beta quantification for patients with dysbetalipoproteinemia (Type III disorder). However, calculated LDL values using the Friedewald equation were found to be significantly higher when compared to beta-quantification in patients with the Type III disorder. There was a slight but significant decrease in LDL-C determined by direct LDL cholesterol assay for non-fasting versus fasting serum (4.7%) despite a strong correlation between these samples (r = 0.98, P <.0001). In addition, freezing samples for 30 days resulted in a significant decrease in levels (15.1%). Thus, this direct LDL cholesterol assay is recommended in place of beta-quantification in hypertriglyceridemic samples (TG > or = 400 mg/dL) and to monitor LDL cholesterol levels in patients with Type III dyslipidemia, because it is less time consuming, more cost-effective and can be adapted to the clinical laboratory. |
| Comparison of antioxidant effects of naringin and probucol in cholesterol-fed rabbits Jeon, S. M., S. H. Bok, et al. (2002), Clin Chim Acta 317(1-2): 181-90. Abstract: BACKGROUND: Due to the strong evidence on the involvement of active oxygen species in a variety of disorders, the role of antioxidants against oxidative stress has recently received increased attention. METHODS: Twenty male rabbits were served a high-cholesterol (HC, 5 g/kg diet) diet or high-cholesterol diet supplemented with naringin (0.5 g/kg diet) or probucol (0.5 g/kg diet) for 8 weeks to compare the antioxidative effects of the citrus bioflavonoid (naringin) and antioxidative cholesterol-lowering drug (probucol). RESULTS: The plasma thiobarbituric acid-reactive substances (TBARS) concentration was not significantly different between the groups, whereas the hepatic TBARS concentration was significantly lower in the probucol group than in both normal and HC control or naringin group. Probucol and naringin supplementation led to an increase in the hepatic superoxide dismutase (SOD) and catalase (CAT) activities, and a decrease in the hepatic mitochondrial hydrogen peroxide (H(2)O(2)) content compared to the HC-control group. However, there was no difference in the cytosolic H(2)O(2) content or cytosolic glutathion peroxidase (GSH-Px) activity in the liver between the groups. Both naringin and probucol supplements significantly increased the plasma vitamin E concentration compared to the HC-control group. As regards the antioxidant enzyme gene expressions, naringin significantly increased the expression of three antioxidant enzyme mRNAs compared to the HC-control group, whereas probucol significantly increased the only SOD mRNA expression. CONCLUSIONS: The probucol supplement was very potent in the antioxidative defense system, whereas naringin exhibited a comparable antioxidant capacity based on increasing the gene expressions in the antioxidant enzymes, while also increasing the hepatic SOD and CAT activities, sparing plasma vitamin E, and decreasing the hepatic mitochondrial H(2)O(2) content. |
| Comparison of antioxidative capacities and inhibitory effects on cholesterol biosynthesis of quercetin and potential metabolites Glasser, G., E. U. Graefe, et al. (2002), Phytomedicine 9(1): 33-40. Abstract: The flavonol quercetin is known to be rapidly metabolized after ingestion by enterocytes and bacteria in the intestinal tract which may influence the biological, e.g. antioxidative potency of this compound. Therefore, quercetin and several of its possible metabolites were compared with regard to their antioxidant activity and their capacity to inhibit hepatocellular cholesterol biosynthesis. Using the 2,2,-diphenylpicrylhydrazyl radical scavenger assay, all compounds with an ortho diphenolic structure acted as strong antioxidants. In contrast, in a cellular assay focusing on lipid peroxidation in cultured rat hepatocytes challenged with tert.-butylhydroperoxide only the lipophilic compounds quercetin and 3,4-dihydroxytoluene were active. Concerning the inhibition of cholesterol biosynthesis, 3,4-dihydroxytoluene surprisingly mimicked the effect of quercetin in primary rat hepatocytes, but much less so in HepG2 cells. All other metabolites were almost ineffective in both cell types. These results suggest that some of the biological functions of flavonoids detectable by in vitro assays may persist in vivo as long as comparably potent metabolites are systemically present. |
| Comparison of aorta and pulmonary artery: I. Early cholesterol accumulation and relative susceptibility to atheromatous lesions Schwenke, D. C. (1997), Circ Res 81(3): 338-45. Abstract: In rabbits, the pulmonary artery and the aorta are susceptible to atherosclerosis. However, susceptibility of the pulmonary artery, compared with the aortic arch, to atherosclerosis and the relationship between the accumulation of cholesterol during the early stages of atherogenesis and the development of atheromatous lesions for these arterial regions remain to be clarified. Cholesterol concentrations for the pulmonary artery and aorta were measured in normal rabbits and in rabbits fed a 0.5% cholesterol diet for 8, 12, and 16 days and 17 weeks. In normal rabbits, the rank order of arterial cholesterol concentrations was pulmonary artery>aortic arch>descending thoracic aorta, with concentrations of total and nonesterified cholesterol 17% and 25% (both P<.05) greater, respectively, for the pulmonary artery than for the descending thoracic aorta. Rank order remained the same during 16 days of cholesterol feeding, but differences between arterial regions were exaggerated. After rabbits were fed cholesterol for 16 days, total and esterified cholesterol concentrations were 57% and 920% (both P<.01) greater, respectively, for the pulmonary artery than for the descending thoracic aorta, with much smaller differences between the aortic regions. In contrast, after rabbits were fed cholesterol for 17 weeks, concentrations of total, esterified, and nonesterified cholesterol were similar for the pulmonary artery and aortic arch, but these forms of cholesterol were increased 100%, 130%, and 53% (all P<.03), respectively, for the aortic arch compared with the descending thoracic aorta. Cholesterol concentrations for the pulmonary artery were positively associated with those for the aortic regions during the first 16 days of cholesterol feeding, but for rabbits fed cholesterol for 17 weeks the associations were either negative or absent. These results indicate that relative rates of cholesterol accumulation in the pulmonary artery and aorta differ at different stages of atherogenesis and suggest that the balance between processes that deliver cholesterol to, and remove cholesterol from, the artery may change in different ways in these arterial regions during atherogenesis. |
| Comparison of appropriateness of cholesterol testing in general practice with the recommendations of national guidelines: an audit of patient records in 20 general practices van der Weijden, T., A. Dansen, et al. (1996), Qual Health Care 5(4): 218-22. Abstract: OBJECTIVE: To compare the profiles of those patients selected by general practitioners for measurement of serum cholesterol with the recommended profiles for opportunistic cholesterol testing described in the national practice guidelines published by the Dutch College of General Practitioners. DESIGN: Retrospective audit of general practitioners' records. MATERIALS: Practice records of 3577 adult patients systematically sampled from 20 general practices. MAIN MEASURES: With criteria set by the national guidelines, the proportion of patients per practice (a) for whom cholesterol testing would be considered justified, and (b) for whom cholesterol testing would be considered unjustified, and the proportion of patients within each of these groups who had had a cholesterol measurement recorded. RESULTS: Cholesterol tests were performed on 415 (11.7%) of the 3577 patients. National guidelines on the management of hypercholesterolaemia state that a positive cardiovascular risk profile is an indication for cholesterol measurement. Just under one fifth (668) of the patients in this study were recorded as having a positive cardiovascular risk profile, but only 31% of these had had their cholesterol measured. Of the patients without recorded evidence of a positive cardiovascular risk profile cholesterol had been measured in 8%. Restricting the analyses to the age group 18-65 (n = 3060) of whom 12.5% had a positive risk profile, did not improve the results. In practices with a computerised information system 37% of patients with recorded evidence of a positive cardiovascular risk profile had had their cholesterol measured. CONCLUSIONS: Cholesterol testing was not targeted as selectively as recommended by the national guidelines. The major problem was failure to test those likely to benefit. Improving the targeting of cholesterol measurements would undoubtedly increase the workload of general practitioners. If the national guidelines are to have an effect on health promotion the first step must be to increase the proportion of patients with positive cardiovascular risk profiles who get their cholesterol tested. A major factor in successfully selecting cases seems to be that practices are equipped with a computerised medical information system. |
| Comparison of biosensors based on entrapment of cholesterol oxidase and cholesterol esterase in electropolymerized films of polypyrrole and diaminonaphthalene derivatives for amperometric determination of cholesterol Vidal, J. C., E. Garcia-Ruiz, et al. (2003), Anal Bioanal Chem 377(2): 273-80. Abstract: Cholesterol amperometric biosensors constructed with enzymes entrapped in electropolymerized layers of polypyrrole and poly-naphthalene derivative polymers are compared. The biosensors are based on entrapment of cholesterol oxidase and/or cholesterol esterase in monolayer or multilayer films electrochemically synthesised from pyrrole, 1,8-diaminonaphthalene (1,8-DAN), and 1,5-diaminonaphthalene (1,5-DAN) monomers. Seven configurations were assayed and compared, and different analytical properties were obtained depending on the kind of polymer and the arrangement of the layers. The selectivity properties were evaluated for the different monolayer and bilayer configurations proposed as a function of the film permeation factor. All the steps involved in the preparation of the biosensors and determination of cholesterol were carried out in a flow system. Sensitivity and selectivity depend greatly on hydrophobicity, permeability, compactness, thickness, and the kind of the polymer used. In some cases a protective outer layer of non-conducting poly(o-phenylenediamine) polymer improves the analytical characteristics of the biosensor. A comparative study was made of the analytical performance of each of the configurations developed. The biosensors were also applied to the flow-injection determination of cholesterol in a synthetic serum. |