Quantitation of high density lipoproteins.
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Adult↗
Biomedical subjects
G R Warnick
Publications and source records attributed to G R Warnick.
A comprehensive evaluation of the heparin-manganese precipitation procedure for estimating high density lipoprotein cholesterol.
The accurate quantitation of high density lipoproteins has recently assumed greater importance in view of studies suggesting their negative correlation with coronary heart disease. High density lipoproteins may be estimated by measuring cholesterol in the plasma fraction of d > 1.063 g/ml. A more practical approach is the specific precipitation of apolipoprotein B (apoB)-containing lipoproteins by sulfated polysaccharides and divalent cations, heparin-Mn(2+) being the most commonly used combination. The present heparin-Mn(2+) procedure was found to be reasonably specific and not often subject to large errors; however, 9% (primarily hypertriglyceridemic samples) of the 966 plasma samples treated with heparin-Mn(2+) had obvious supernatant turbidity, indicating incomplete sedimentation of apoB-associated lipoproteins. Furthermore, 48% of the nonturbid supernates contained more than 1 mg/dl (mean 2.5 mg/dl) of apoB-associated cholesterol when measured by a radial immunodiffusion procedure, indicating slight overestimation of HDL cholesterol. Determination of the extent of the unprecipitated apoB-associated lipoproteins by sensitive radioimmunoassay and of the amount of precipitated high density lipoprotein by radial immunodiffusion assay of apolipoproteins A-I and A-II at various heparin and Mn(2+) concentrations indicated that the usual heparin level (approximately 1.3 mg/ml) was adequate. However, a twofold increase in Mn(2+) concentration to 0.092 M improved precipitation of the apoB-associated lipoproteins without excessive precipitation of high density lipoprotein from plasma. This increased Mn(2+) level also provided improved sedimentation of the apoB-associated lipoproteins from hypertriglyceridemic plasma. Additional observations suggested that, for convenience, the heparin and Mn(2+) can be added simultaneously as a combined reagent, that samples can be incubated for 10 minutes at room temperature before centrifugation, and that turbid supernates from hypertriglyceridemic samples can usually be made free of apoB-associated lipoproteins by centrifugation at 12,000 g for 10 minutes.
Apolipoproteins↗
Multi-laboratory comparison of three heparin-Mn2+ precipitation procedures for estimating cholesterol in high-density lipoprotein.
Plasma high-density lipoprotein is commonly estimated by measuring the cholesterol remaining in plasma supernatant solutions after other lipoproteins, which contain apolipoprotein B, are precipitated with heparin and Mn2+. The method (method I) now in use by the Lipid Research Clinics, in which Mn2+ is at 46 mmol/liter final concentration, is reasonably accurate, but precipitation and sedimentation of lipoproteins other than high-density lipoproteins is often incomplete. We evaluated two modifications of method I. In method II, the Mn2+ concentration was doubled; the second modification (method III) included the increased Mn2+ concentration in a combined heparin Mn2+ reagent, decreased sample volume (2 ml), and a shorter incubation time (10 min at room temperature). The percentages of samples with turbid supernates (i.e., incomplete sedimentation) by methods I, II, and III were 9, 3, and 2%, respectively. Among non-turbid supernates, the percentages of samples containing measurable apolipoprotein B (incomplete precipitation) were 79, 19, and 16%, respectively. We conclude that method III is the most convenient and accurate of the three procedures.
Chemical Precipitation↗
Heparin--Mn2+ quantitation of high-density-lipoprotein cholesterol: an ultrafiltration procedure for lipemic samples.
We describe a modified heparin--Mn2+ procedure for high-density-lipoprotein cholesterol quantitation, especially in lipemic samples. High-density-lipoproteins may be estimated as cholesterol remaining in plasma supernates after precipitation of other lipoproteins by heparin and Mn2+ treatment. However, in lipemic samples or those from non-fasting individuals, the lower density of the precipitated chylomicrons, very-low-, and low-density-lipoproteins frequently prevents their sedimentation by the usual low-speed centrifugation, and high-density-lipoprotein cholesterol thus is overestimated in the resulting turbid supernates. Sedimentation is improved by a twofold increase in Mn2+ concentration to 92 mmol/liter. The procedure reported here produced clear supernates in more than 95% of samples tested. Any remaining turbid supernates can be cleared by a simple, convenient ultrafiltration technique. The filtration removed essentially all of the very-low- and low-density-lipoproteins without removing appreciable amounts of high-density-lipoproteins.
Apolipoproteins↗
Type III hyperlipoproteinemia: a comparative study of current diagnostic techniques.
Research into the prevalence, genetic transmission and pathophysiology of Type III hyperlipoproteinemia has suffered from the lack of a practical specific diagnostic procedure. In this study, very low density lipoprotein (VLDL) compositional criteria were established in a population lacking the beta-migrating VLDL characteristic of this disorder. Diagnosis by these criteria was compared to diagnosis using current criteria for the Type III lipoprotein pattern. In addition two techniques for detecting Type III without preliminary VLDL isolation by ultracentrifugation were evaluated. Plasma triglyceride (TG) concentration dependent cutlines for the compositional criteria reduced false positives at low TG levels and false negatives at high TG levels. Furthermore, an agarose electrophoresis heparin-manganese precipitation technique was effective for screening for a possible Type III pattern in plasma whereas the combination agarose-polyacrylamide gel electrophoresis system was not effective.
Cholesterol↗
Physiological and analytical variation in cholesterol and triglycerides.
Plasma cholesterol and triglyceride levels were determined, on each of two AutoAnalyzer systems in 11 healthy subjects, weekly over a 10-week and monthly over a 12-month period. Analytical variation was 1-2% for cholesterol and 2-5% for triglyceride. Cholesterol and triglyceride values on frozen quality control serum pools were not indicative of absolute values on fresh plasma. Even though the two AutoAnalyzer systems averaged within 1-2 mg/dl for triglyceride and cholesterol on the serum quality control pools during the 12-month period, the two systems differed by 7-8 mg/dl on fresh or frozen plasma samples. The coefficient of physiological variation on the 10 weekly samples averaged 5% (range 3-10%) for plasma cholesterol and 18% (range 9-27%) for plasma triglyceride. Analysis of the monthly samples suggested significant (P less than 0.05) seasonal trends: cholesterol was highest in the winter months and lowest in October, whereas triglyceride was highest in January and February and lowest in May and December. We conclude that intra-individual variation can be an important source of error in attempting to make a genetic diagnosis of hyperlipidemia and/or in evaluating hypolipidemic regimens in a given subject.
Adult↗
Lp(a) lipoprotein: relationship to sinking pre-beta lipoprotein hyperlipoproteinemia, and apolipoprotein B.
To assess the relationship between the Lp(a) and the "sinking pre-beta" (d smaller than 1.006) lipoprotein, the concentration of Lp(a) was quantified by radial immunodiffusion and the presence or absence of sinking pre-beta was assessed by agarose electrophoresis in overnight fasting plasma samples from 485 adults, comprised of 320 with normal lipid levels, 48 with type IIa, 40 with type IIb, and 77 with type IV lipoprotein phenotypes. The median Lp(a) level was 7.6 mg/100 ml, 89% (433 of 485) having detectable Lp(a) levels. Twenty-two per cent (107 of 485) had detectable pre-beta lipoprotein in the d greater than 1.006 plasma fraction (sinking pre-beta). Of the sinking pre-beta positive plasma samples, 96% (102 and 107) exceeded the median Lp(a) level, and sinking pre-beta was detected in all 44 samples with an Lp(a) concentration exceeding 40 mg/100 ml. The relationship of Lp(a) and sinking pre-beta to lipoprotein phenotype was assessed. Compared to the normolipidemic group, the type IIa group had higher Lp(a) percentile values (p smaller than 0.02), whereas the IIb and type IV groups had significantly lower Lp(a) values than the normolipidemic group. Ninety-two per cent (296 of 320) of the normolipidemic subjects had detectable levels of Lp(a) and 22% (70 of 320) had detectable sinking pre-beta lipoprotein. Ninety-four per cent (45 of 48) of the type IIa plasmas had detectable Lp(a) levels and 27% (13 of 48) had sinking pre-beta lipoproteins. Contrasted with the IIa group, only 80% (32 of 40) of the IIb plasmas had detectable Lp(a) levels and 18% (7 of 40) had sinking pre-beta lipoprotein. In the type IV plasmas 78% (60 of 77) had detectable Lp(a) and 22% (17 of 77) had sinking pre-beta lipoprotein. Lp(a) or log Lp(a) levels were not correlated with apolipoprotein B levels (n = 485, r = 0.002 or 0.037, respectively). Furthermore, Lp(a) levels remained essentially constant in three subjects whose aprptein B levels were altered in response to pharmacological and/or dietary manipulation. A fourth subject had a 50% increase in Lp(a) but this change did not correlate with apoprotein B changes. Thus, these findings suggest that Lp(a) is metabolically independnet of low density lipoprotein even though it shares the same structural protein, apoprotein B.
Adult↗
Regulation of prophyrin biosynthesis. Purification and characterization of -aminolevulinic acid synthase.
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5-Aminolevulinate Synthetase↗
Multicenter evaluation of a patient-administered test for blood cholesterol measurement.
BACKGROUND: In order to assess accuracy of a newly developed, noninstrumented, self-administered fingerstick test that measures cholesterol levels in whole blood, the AccuMeter Cholesterol Self-Test was evaluated for home-use by untrained consumers in a multicenter study. METHODS: A total of 486 untrained adult volunteers of varying age, occupation, and educational background were recruited at four sites. Participants received written instructions provided in the kit, access to a telephone "800" number for additional help, and, if necessary, a short instructional video available to consumers on request. Fingerstick cholesterol results obtained by untrained volunteers were compared with paired venous serum results obtained by the Abell-Kendall cholesterol reference method. After application of exclusion criteria, 79.0% (384/486) of subjects had AccuMeter fingerstick results available for comparison with the reference method. RESULTS: Results obtained with the AccuMeter test correlated well with the Abell-Kendall results (r = 0.91). There was a mean overall bias for the AccuMeter of -0.116 +/- 0.528 mmol/liter (-2.2%), with a mean absolute bias of 0.398 +/- 0.367 mmol/liter (7.6%). Biases at the National Cholesterol Education Program cutpoints of 5.20 and 6.20 mmol/liter were -2.2 and -2.5%, respectively. Subjects with high-risk total cholesterol values (> or = 6.20 mmol/liter) were correctly classified 80.0% of the time, with an additional 18.8% placed in the borderline category (5.20-6.20 mmol/liter); 1.2% were inappropriately placed in the desirable category. No subjects were placed in the high-risk category by the AccuMeter test if they had a desirable cholesterol value by the reference method, while 9.8% were placed in this category if they were in fact borderline. CONCLUSIONS: This test appears to be a useful addition to available options in the effort to increase awareness of cholesterol as a heart disease risk factor. A large portion of untrained consumers were able to perform the AccuMeter Cholesterol Self-Test and obtain comparable results to the reference method. This test for the first time allows consumers to determine their own cholesterol values, with a reasonably good degree of accuracy.
Adolescent↗
Changes in plasma lipids and dietary intake accompanying shifts in perceived workload and stress.
Plasma lipids, dietary intake, and self-reported stress and workload were assessed in 14 employees twice before major work deadlines (high workload), and once during a comparatively quiescent period of work (low workload). Increases in self-reported stress and workload between the high and low workload periods were significantly positively associated with increases in plasma total cholesterol, although lipid levels were not increased in the group as a whole during the high workload periods. Dietary intake of calories, total fat, and percentage of calories from fat were significantly higher during high workload during a period of high workload is associated with elevated total cholesterol and that dietary intake of foods which raise cholesterol levels is also increased. Further studies of larger groups of subjects may be required to show a frank increase in cholesterol with increased workload.
Adult↗
Hyperlipidemia in the Pacific Northwest Bell Telephone Company Health Survey. Part 1. Lipoprotein cholesterol and triglyceride concentrations.
Lipoprotein triglyceride and cholesterol concentrations and characteristics are described in normolipidemic and in three categories of hyperlipidemic subjects participating in the Pacific Northwest Bell Telephone Company Health Survey. For this study, 350 white participants 20 to 59 years of age with cholesterol or triglyceride values exceeding the age, sex, and hormone-use specific, population-based 90th percentile values were defined as having hypercholesterolemia, hypertriglyceridemia, or combined hyperlipidemia; 722 participants were classified as normolipidemic. In hypercholesterolemia, very low density lipoprotein cholesterol and triglyceride and high density lipoprotein cholesterol concentrations were higher than in normolipidemia. In hypertriglyceridemia, high density lipoprotein cholesterol was significantly lower in men and women not using sex hormones and low density lipoprotein triglyceride was significantly higher in men and women using hormones compared to normolipidemia. In combined hyperlipidemia, high density lipoprotein cholesterol concentrations were lower than in normolipidemia, but higher than in pure hypertriglyceridemia. The presence of beta migrating very low density lipoprotein and chylomicrons was seen primarily in hypertriglyceridemic or combined hyperlipidemic men. Sinking prebeta lipoprotein was equally common (20%) among all normolipidemic and hypercholesterolemic subjects, but was less common (5% to 10%) in hypertriglyceridemic and combined hyperlipidemic men and female hormone users. Quantitative and qualitative lipoprotein abnormalities associated with hyperlipidemia were found to vary by gender and by sex hormone use in women and were often, but not always, more marked in men.
Adult↗
Hyperlipidemia in the Pacific Northwest Bell Telephone Company Health Survey. Part 2. Lipoprotein lipid interrelationships.
The relationships of lipoprotein cholesterol and triglyceride among lipoprotein fractions have potential significance for understanding atherogenesis and distinguishing among different classes of hyperlipidemia. We have compared these relationships in normolipidemic, hypercholesterolemic, hypertriglyceridemic, and combined hyperlipidemic participants in the Pacific Northwest Bell Telephone Company Health Survey. The cholesterol/triglyceride ratio in each lipoprotein fraction was moderately higher (1% to 26%) in hypercholesterolemia but significantly lower (20% to 50%) in hypertriglyceridemia, compared to normolipidemia. In combined hyperlipidemia, the very low density lipoprotein ratios were lower than in normolipidemia, but larger than in hypertriglyceridemia. These changes were directionally the same, but differed quantitatively, in both men and women. Correlation coefficients between cholesterol and triglyceride within each fraction varied by gender and sex hormone use. The largest correlations were seen in combined hyperlipidemic men for very low density lipoproteins, normolipidemic men for low density lipoproteins, and combined hyperlipidemic women taking hormones for high density lipoproteins. The correlation of very low and low density lipoprotein cholesterol was generally negative and was strongest for hormone users (r = -0.81) and weakest for nonusers (r = -0.06). Very low density lipoprotein triglyceride and high density lipoprotein cholesterol correlations were generally negative and were strongest in hypertriglyceridemic women not taking hormones (r = -0.55) and weakest in normolipidemic hormone users (r = -0.10). This correlation was positive for hypertriglyceridemic and combined hyperlipidemic hormone users.
Adult↗
Epidemiological correlates of high density lipoprotein subfractions, apolipoproteins A-I, A-II, and D, and lecithin cholesterol acyltransferase. Effects of smoking, alcohol, and adiposity.
Recent data suggest that the protection against ischemic heart disease afforded by high density lipoprotein (HDL) cholesterol (C) may be concentrated in the HDL2 subfraction. To examine the behavioral correlates of the HDL subfractions, we recalled 33 men and 17 women of a random sample from the Pacific Northwest Bell Telephone Company Health Survey. Adiposity and very low density lipoprotein (VLDL) triglyceride were negatively correlated with HDL2C. Smoking was not correlated with HDL2C, but was negatively correlated with HDL3C (men, rs = -0.635, p = 0.001; women, rs = -0.534, p = 0.014); this relationship was independent of alcohol consumption, adiposity, and VLDL triglyceride. Alcohol consumption was also more strongly related to HDL3C (men, rs = 0.248, p = 0.082; women, rs = 0.586, p = 0.007). Lecithin cholesterol acyltransferase (LCAT) mass was negatively related with HDL2C, but was positively correlated with HDL3C and apolipoprotein A-II. Smoking was negatively correlated with LCAT mass. Since it is believed that HDL3C is not associated with the risk of ischemic heart disease and since both smoking and alcohol consumption may mainly affect HDL3C, the current study suggests that the increase in risk of ischemic heart disease with smoking and the possible decrease with alcohol consumption may be mediated through mechanisms other than their effects on HDLC.
Adult↗
Postheparin plasma triglyceride lipases. Relationships with very low density lipoprotein triglyceride and high density lipoprotein2 cholesterol.
Hepatic triglyceride (HTGL) and lipoprotein lipase (LPL) probably have major roles in the removal of triglyceride from triglyceride-rich lipoprotein and in the formation of high density lipoprotein (HDL). However, no population-based study of their activity and relationship to lipoprotein lipid levels has been reported. To determine these relationships, we recalled 33 men and 17 women of a randomly selected sample of the Lipid Research Clinics Pacific Northwest Bell Telephone Company Health Survey. The subjects were 53 +/- 7 years old (mean +/- SD) with total triglyceride levels of 120 +/- 57 mg/dl and total cholesterol levels of 224 +/- 35 mg/dl. Postheparin plasma LPL activity (127 +/- 61 nmol/min/ml) was not significantly correlated with either age, sex, or adiposity. In contrast, HTGL activity was significantly higher in men (235 +/- 84 nmol/min/ml) than women (170 +/- 91 nmol/min/ml, p less than 0.02), and was correlated with age in men and with adiposity in women. In both men and women, HTGL activity was related positively with VLDL triglyceride and inversely with HDL2 cholesterol. When the association between HTGL activity and VLDL triglyceride was examined with values from men and women pooled, the relationship was not weakened after adjustment for the linear effect of sex, adiposity, LPL, or HDL2 cholesterol.
Adult↗
Comparison of plasma lipoproteins and apoproteins in Chinese and American non-insulin-dependent diabetic subjects and controls.
Plasma lipoproteins and apoproteins were compared among Chinese and American controls and non-insulin-dependent diabetic (NIDDM) subjects in the same laboratory. Apoprotein AI concentrations in Chinese subjects, both NIDDM subjects and controls (men, 147 and 158 mg/dl, respectively), were significantly higher than those in American subjects (men, 104 and 124 mg/dl, respectively). Apoprotein AII concentrations, however, were comparable between Chinese and American subjects. Chinese NIDDM subjects had lower high-density lipoprotein cholesterol (HDLC), higher low-density lipoprotein cholesterol (LDLC), and higher apoprotein B levels than Chinese controls. Chinese subjects with NIDDM had HDLC and LDLC levels similar to those of American controls but trends of higher HDLC and lower LDLC compared with American subjects with NIDDM. These differences may in part explain the relatively higher incidence of atherosclerotic vascular disease in Americans.
Apolipoproteins↗