The effect of aggressive and moderate lowering of LDL-cholesterol and low dose anticoagulation on plasma lipids, apolipoproteins and lipoprotein families in post coronary artery bypass graft trial.

The reported results (The Post Coronary Artery Bypass Graft Trial Investigators. The effect of aggressive lowering of low-density lipoprotein cholesterol levels and low-dose anticoagulation on obstructive changes in saphenous-vein coronary-artery bypass grafts. New Engl J Med 1997;336:153-162) of the Post Coronary Artery Bypass Graft (Post CABG) trial have shown that aggressive lowering was more effective than moderate lowering of low density lipoprotein (LDL) cholesterol in reducing the progression of atherosclerosis in saphenous-vein grafts (27 vs. 39%; P < 0.001); low dose warfarin had no effect on the progression of atherosclerosis. The present report describes the effect of long-term (an average of 4.3 years) aggressive treatment with high (40-80 mg/day) and moderate treatment with low (2.5-5 mg/day) doses of lovastatin on lipids, apolipoproteins (apo) and apoA- and apoB-containing lipoprotein families. To achieve the target LDL-cholesterol levels (60-85 mg/dl for aggressive group and 134-140 mg/dl for moderate group), cholestyramine (8 g/day) was given to 25% of subjects on aggressive and 5% of subjects on moderate treatment. Although with both treatment strategies there were significant decreases (P<0.001) in the levels of total cholesterol, LDL-cholesterol, apoB, LDL-apoB and cholesterol-rich Lp-B family, percent changes in the levels of these variables were greater in the aggressive- than in the moderate-treatment groups. These treatments had only marginal effects in increasing the levels of high density lipoprotein cholesterol, apoA-I and Lp-A-I and Lp-A-I:A-II families. The long-term aggressive treatment exerted no effect on the concentrations of triglycerides, apoC-IlI, apoC-III in VLDL + LDL and triglyceride-rich Lp-Bc families. Neither treatment affected the levels of Lp(a). The potentially modifying influence of warfarin and apoE phenotypes on lovastatin-induced changes in lipoprotein variables was found to be of little significance. It is likely that the beneficial effect of lovastatin in reducing the progression of atherosclerosis in grafts is mediated through its specific lowering effect on cholesterol-rich Lp-B particles.

Lipids and apolipoproteins in growth hormone-deficient children during treatment.

The role of growth hormone (GH) in regulating the transport of plasma lipoproteins has not been clearly defined, but past studies suggest that GH may influence cholesterol levels. This protocol was designed to evaluate possible changes in lipid and apolipoprotein status in GH-deficient children and children with neurosecretory dysfunction (NS) before GH therapy and at intervals after GH therapy was started. Twenty children with classic GH deficiency were evaluated, and 28% were hyperlipidemic at the onset of the study. Seven children were evaluated in the NS group, and only one (14%) showed an elevated total cholesterol (TC) greater than 200 mg/dL. The mean TC for all the GH-deficient children was elevated above the normal range, but not for the NS group. The mean apolipoprotein (apo) C-III level and its heparin-precipitated fraction (HP) were also elevated in the GH-deficient group, but only the apo C-III HP was elevated in the NS group. A standard replacement dose of recombinant methionyl GH was used, and therapy had no significant effect on TC or triglyceride (TG) levels. Apo C-III HP, a marker of hypertriglyceridemia, increased after the start of therapy, but no other lipoprotein levels changed significantly in the GH-deficient group. No changes were seen with treatment in the NS group. The longitudinal design of this study allowed demonstration of the later changes in the apolipoproteins and the presence of a distinct subset of patients with both GH deficiency and hypercholesterolemia. This study supports the role of GH in modulating lipid metabolism.

Lack of effect of probucol on atheroma formation in cholesterol-fed rabbits kept at comparable plasma cholesterol levels.

Rabbits were fed cholesterol for 14 weeks to study the effect of probucol on atheroma formation. Three groups of animals were investigated: group CHOL was fed 1% cholesterol and served as control for group P + CHOL. fed 1% cholesterol and 1% probucol from the onset till the end of the experiment: group CHOL + P received 1% cholesterol throughout the experiment and 1% probucol during the last 4 weeks only. Plasma cholesterol concentrations were monitored at frequent intervals and were modulated by dietary perturbations so that the areas under the curve expressing plasma cholesterol changes with time, were similar in probucol and non-treated rabbits. The efficacy of long-term probucol treatment was evidenced by a significant reduction in plasma apolipoprotein A-I throughout the experiment and lower plasma TBARs during the first 6 weeks, when the hypocholesterolemic effect of probucol was also seen. Two weeks prior to the termination of the experiment, the rabbits were injected with rabbit plasma labeled with [3H]cholesteryl linoleyl ether [( 3H]CLE). Aortic atheromatosis was quantified by determination of total and cholesteryl ester (CE). The aortic cholesterol content was related to the arch, thoracic and abdominal segments, to the surface area of each segment or its dry defatted weight. Total and esterified cholesterol were highest in the aortic arch in all 3 groups when related to any of the above mentioned parameters. No statistically significant difference in aortic total cholesterol and CE content was seen among the three groups studied. The [3H]CLE recovered in the aortic segment correlated with the CE content and the [3H]CLE (dpm)/mg CE in all segments was similar. No statistically significant difference in the [3H]CLE recovered in the aortic segments among the 3 groups was seen. We conclude that in cholesterol-fed rabbits, in which the plasma cholesterol levels were maintained at comparable levels, probucol treatment did not affect plasma CE influx into the aorta and did not attenuate development of aortic atherosclerosis.

Plasma lipids and apolipoproteins in a 13-year-old boy with diabetic ketoacidosis and extreme hyperlipidemia.

A 13-year-old boy with untreated diabetes presented in severe ketoacidosis (DKA) for the first time with an initial triglyceride (TG) level of 14,461 mg/dl. Serial blood samples were drawn to determine the interrelationships of changes in lipids and apolipoproteins during treatment with insulin and intravenous fluids. The TG level declined to 122 mg/dl in 7 days concomitant with a lowering of apolipoproteins C-II, C-III, E, D, and F. Further observations suggested that the TG-rich lipoproteins underwent degradation associated with a decline in the levels of apolipoproteins associated with very low density lipoprotein (VLDL) in contrast to an increase in high density lipoprotein-cholesterol (HDL-C), ApoA-I and ApoA-II. ApoB and low density lipoprotein cholesterol (LDL-C) were increased transiently. Subsequent therapy with continuous subcutaneous insulin infusion (CSII) were effective in maintaining glucose homeostasis and normolipidemia for 6 months.

Increased levels of HDL-cholesterol and apolipoprotein A-I after intensified insulin therapy for diabetes.

Sixteen subjects with insulin-dependent diabetes mellitus were studied to determine whether changes in plasma lipids and apolipoproteins follow intensified control using preprandial doses of regular insulin with an additional dose of NPH insulin before bedtime. The mean total dialy dose of insulin was increased from 1.03 +/- 0.09 to 1.17 +/- 0.44 units/kg throughout the six-month period. Levels of HDL-cholesterol and apolipoprotein A-I increased without significant changes in hemoglobin A1 (HbA1), triglyceride, or cholesterol. These findings suggest that increases in HDL-cholesterol and apolipoprotein A-I were a result of the intensified insulin delivery.

Quantitative determination of human plasma apolipoprotein A-I by a noncompetitive enzyme-linked immunosorbent assay.

A noncompetitive enzyme-linked immunosorbent assay (ELISA) for human plasma apolipoprotein A-I (ApoA-I) was developed. Microtiter plates were coated with purified antibodies to ApoA-I and blocked. Plasma samples from normolipidemic and hypertriglyceridemic subjects were added and ApoA-I was allowed to bind to coating antibodies. After washing, the amount of ApoA-I bound to microtiter plates was estimated with horseradish peroxidase-labeled antibodies to ApoA-I. A single step delipidization procedure was included to expose masked antigenic sites of ApoA-I in plasma. The average concentration of ApoA-I in plasma of normolipidemic subjects was 1.37 g/l. Recovery of ApoA-I added to plasma varied from 93-107%. Intra- and inter-assay coefficients of variations were 4 and 8%, respectively. The assay was also used for quantifying ApoA-I in lipoprotein density classes. There was a good correlation between this assay and electroimmunoassay (r = 0.84-0.92). The described sandwich ELISA is a specific, precise, sensitive and relatively simple method for measuring ApoA-I levels in human plasma.

Studies of lipids, lipoproteins, and apolipoproteins in Menkes' disease.

Three patients with Menkes' disease, an inherited disorder of copper transport, were studied to determine whether the copper deficiency was associated with a lipoprotein disorder. Hypocuprinemia was documented in all three cases. Two patients had severe copper and ceruloplasmin deficiencies, whereas the third patient had a less severe deficiency. Hypertriglyceridemia was observed in the first patient, and elevations in triglyceride, cholesterol, apolipoprotein B (ApoB), and apolipoprotein C-III (ApoC-III) occurred predominantly in the very low density lipoprotein fraction (VLDL). This patient had normal lipoprotein lipase activity but mild glucose intolerance. The second patient had a borderline high cholesterol level with normal plasma triglycerides and apolipoproteins, whereas the third patient appeared to have normal total cholesterol but slightly higher triglycerides with elevated plasma apolipoprotein E (ApoE). No striking differences were observed in the chemical composition of all lipoprotein subfractions between patients and controls except that the neutral lipid content of VLDL was higher in patients than in controls. The ApoB was initially normal in molecular weight but degraded faster than the controls during storage. The appearance of the major low density lipoprotein (LDL) fraction of the first two patients was opaque white, in contrast to clear yellow in the third patient and in the age- and diet-matched controls. This abnormal appearance of LDL in these patients was associated with low plasma levels of beta-carotene and ceruloplasmin. These findings suggest that decreased serum copper levels may be associated with lipid and lipoprotein abnormalities and may enhance lipid peroxidation of LDL accounting for the color change.(ABSTRACT TRUNCATED AT 250 WORDS)

Use and significance of reference serum as a secondary standard for electroimmunoassay of apolipoprotein A-I.

This study was designed to show the effect of different primary standards and antisera on the variability of concentrations of apolipoprotein A-I (ApoA-I) in plasma and to document the usefulness of reference sera as a secondary standard in the electroimmunoassay of this apolipoprotein. We compared the reactivities of two separate ApoA-I samples and a preparation of high-density lipoprotein (HDL3) with seven different antisera to ApoA-I. The antisera reacted differently with each of the three standards, as shown by the different slopes of their standard curves. The resulting inconsistencies in the ApoA-I values for unknown plasma samples were shown to be corrected by the use of a reference serum. When ApoA-I analyses were carried out with the reference serum as a standard, all seven antisera gave statistically indistinguishable results for concentrations of plasma ApoA-I. The use of reference sera thus represents the simplest and most convenient means of standardizing the electroimmunoassay for ApoA-I.

Growth hormone in the regulation of hyperlipidemia.

Plasma concentrations of triglyceride, cholesterol, and apolipoproteins A-I and B in young growth hormone deficient subjects were measured at intervals during the five weeks after initial hormone-replacement therapy. The mean concentrations of cholesterol, apolipoproteins A-I and B decreased significantly during that period: the decreases were progressive and in similar proportion to each other. Also, the amount by which apolipoprotein A-I concentration decreased was correlated with its plasmas concentration before treatment. The data suggests that growth hormone may play a role in the regulation of these three major plasma lipoprotein components and tend to suppress the development of hypercholesterolemia which has been observed in some adult growth hormone deficient subjects.

Plasma apolipoprotein concentrations in familial apolipoprotein A-I and A-II deficiency (Tangier disease).

Familial apolipoprotein A-I and A-II deficiency (Tangier disease) is characterized by cholesterol ester deposition in histiocytes, decreased plasma cholesterol and low density lipoprotein cholesterol (C-LDL), and a striking deficiency of high density lipoproteins (HDL). We measured plasma lipid, lipoprotein cholesterol, and plasma apolipoprotein (apo) A-I, A-II, B, C-I, C-II, C-III, D, and E concentrations in 7 Tangier homozygotes, 2 obligate heterozygotes, and 50 normal subjects. Heterozygotes had modest reductions in high density lipoprotein cholesterol (C-HDL), plasma apoA-I, and apoA-II levels. Mean concentrations (+/- SD) of plasma C-HDL and apolipoproteins A-I, A-II, B, C-I, C-II, C-III, D, and E in mg% in normals were: 50 +/- 14, 134 +/- 24, 68 +/- 18, 98 +/- 20, 7 +/- 2, 3.7 +/- 2, 13 +/- 5, 10 +/- 4, and 10 +/- 4, respectively; and in homozygotes were: 1 +/- 1, 1.3 +/- 0.7, 4.8 +/- 2.5, 82.6 +/- 18, 4.1 +/- 1.7, 2.3 +/- 0.9, 6.5 +/- 3.8, 2.2 +/- 0.5, +/- 3.1, respectively. Homozygotes had C-HDL, apoA-I and apoA-II levels which were 2%, 1%, and 7% (p less than .001) of normal, respectively, and mean levels of apolipoproteins B, C-I, C-II, C-III, D, and E which were 84%, 59%, 62%, 50%, 22%, and 54% of normal, respectively. There was heterogeneity of these latter apolipoprotein concentrations among homozygotes. Mean apoC-I, apoC-III, apoD, and apoE levels were significantly less than normal (pp less than .05) in homozygotes. These data indicate that homozygotes have variable but generally decreased apoC and apoE levels, a deficiency of apoD, and a striking reduction in plasma apoA-I and apoA-II concentrations.

Quantitative determination of apolipoproteins C-I and C-II in human plasma by separate electroimmunoassays.

Separate electroimmunoassays are described for measuring human plasma apolipoproteins C-I and C-II. Purified apolipoproteins C-I and CII were used in preparing monospecific antisera and as the primary standards. These assays are sensitive (maximal sensitivity, 20 ng), specific, rapid, precise (the within- and between-assay coefficients of variation for both assays were 5 and 8%, respectively), and accurate (accuracy was based on comparison of calculated and measured C-I, C-II, and C-III contents of an ApoC-containing column-eluent fraction) and are applicable to measurement of C-I and C-II polypeptides in whole plasma and density classes. However, plasma samples with triglyceride (triacylglycerol) concentrations greater than 6000 mg/L must be delipidized before analysis for C-II, as must those with greater than 12 000 mg/L before analysis for C-I polypeptide. Mean concentrations (and SD) of C-I in plasma of normolipidemic subjects and hyperlipoproteinemic phenotypes IIa, IIb, IV, and V were 60 (15), 70 (20), 100 (20), 100 (20), and 260 (94) mg/L, respectively. The corresponding C-II values were 40 (20), 43 (20), 68 (20), 65 (20), and 210 (70), respectively. C-I and C-II concentrations in patients with phenotypes IIb v, IV, or V significantly (p less than 0.001) exceeded those in normal persons or phenotype IIa. The observed correlations (r = 0.92 and r = 0.94) between triglyceride and C-I and C-II values suggest that these two polypeptides, like C-III, are excellent plasma markers for assessing the state of triglyceride metabolism.

Quantitative determination of human apolipoprotein C-III by electroimmunoassay.

An electroimmunoassay procedure is described for the quantitative determination of human plasma apolipoprotein C-III. Purified apolipoprotein C-III was used for the preparation of monospecific antisera and as the primary standard. This sensitive, specific, rapid (time required for the completion of the assay is 5 h), precise (the within and between-assay coefficients of variation are 6 and 8%, respectively) and accurate electroimmunoassay is applicable to measurement of C-III polypeptide in whole serum and density classes. However, plasma samples containing lipoproteins with Sf less than 400 and/or triacylglycerol levels greater than 700 mg/100 ml must be delipidized. Plasma apolipoprotein C-III levels of normolipidemic subjects and hypercholesterolemic (type IIa) patients were similar (10.4 +/- 3 and 12.0 +/- 6 mg/100 ml, respectively). In contrast, patients with hyperlipoproteinemic phenotypes IIb, III, IV and V had significantly increased levels of apolipoprotein C-III (22 +/- 7; 23 +/- 6, and 54 +/- 12, respectively). The levels of apo C-III in patients with type V were significantly higher (P less than 0.001) than in normal or other hyperlipoproteinemic phenotypes.