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The effects of chlorthalidone, 100 mg/d given for 6 weeks, on serum lipids and lipoproteins were assessed in 22 premenopausal and 18 postmenopausal women. In the latter, chlorthalidone significantly increased total serum cholesterol (13%, p less than 0.001), low-density-lipoprotein (LDL) cholesterol (21%, p less than 0.001) and apoprotein B (16%, p less than 0.05). In contrast, these values were not altered in the premenopausal group. Levels of LDL cholesterol, high-density-lipoprotein cholesterol, total and very-low-density triglycerides, apoproteins A1 and A2, and plasma volume, plasma glucose, insulin, epinephrine, estradiol, and free fatty acids were unchanged in both groups. Chlorthalidone-induced changes in levels of LDL cholesterol did not correlate significantly with variations in blood pressure, plasma potassium, uric acid, renin, aldosterone, or norepinephrine levels. These findings indicate that the thiazide-like diuretic chlorthalidone increases serum LDL cholesterol in postmenopausal but not in premenopausal women.

The subcellular distributions of acidic (pH 4.5) and neutral (pH 7.5) longchain triacylglycerol lipases (glycerol ester hydrolase, EC 3.1.1.3) of pig liver have been determined. The distribution of the acidic lipase closely paralleled that of the lysosomal marker enzyme, cathepsin D. Approx. 60% of the neutral lipolytic activity resided in the soluble fraction;the distribution of this activity failed to parallel that of marker enzymes for mitochondria, lysosomes, microsomes, or plasma membranes. A method has been developed for purification of the neutral lipase from the soluble fraction by ultracentrifugation. An approximate 90-fold purification was achieved, with recovery of 16% of the initial activity. The partially purified neutral lipase exhibited a pH optimum between 7.25 and 7.5. It required 30 mM emulsified triolein for optimal activity and ceased to liberate fatty acids after 30 min of incubation. The enzymatic activity was destroyed by heating at 60 degrees C. Neutral lipase was inhibited by sodium deoxycholate, Triton X-100 and iodoacetamide. The activity was not inhibited by sodium taurocholate, EDTA, heparin and diethyl-p-nitrophenyl phosphate. Neutral lipase failed to exhibit activity in assay systems specific for lipoprotein lipase, monoolein hydrolase, tributyrinase, and methyl butyrate esterase and showed little or no capacity to hydrolyze chyle chylomicrons or plasma very low density lipoproteins. It is suggested that the function of neutral lipase may be to supply the liver with fatty acids liberated from endogenously synthesized or stored triacylglycerols.

This study describes a variant of hypo-alpha-lipoproteinemia in a 57-year-old male patient. The total plasma cholesterol level was 258 mg/dl with 64% in esterified form. The concentration of triglycerides was 205 mg/dl. The lipoprotein electrophoretic pattern revealed the absence of alpha-lipoproteins, whereas the other lipoproteins showed an intermediate electrophoretic mobility. The concentration of HDL cholesterol (heparin: MgCl2 precipitation) was extremely low (3 mg/dl). The activity of lecithin; cholesterol acyltransferase (LCAT) and the postheparinlipolytic activity were within the normal range. Determination of apolipoproteins revealed a marked deficiency of both apoprotein A-I (17 mg/dl) and apolipoprotein A-II (11 mg/dl). The concentration of apolipoprotein-B was elevated (186 mg/dl). Unlike the clinical manifestations of Tangier disease, our patient did not show skin lesion, abnormal tonsils, hepatosplenomegaly, peripheral neurologic abnormalities or corneal deposits. Also in contrast to Tangier disease our patient had coronary artery disease with myocardial infarction accompanied with severe occlusive peripheral arterial disease.

Lipoproteins in newborn plasma were isolated from a minimal sample amount (0.3 ml) by a single-step ultracentrifugation in a density gradient, spanning the density range 1.02-1.20 g/ml. After 66 h ultracentrifugation in a swinging-bucket rotor, the content of the tube was eluted and collected in 0.4 ml fractions. Cholesterol and apoproteins AI, AII, and B were assayed in each fraction yielding both the distribution and composition of the very low density lipoprotein (VLDL), low density lipoprotein (LDL), high density lipoprotein (HDL2, HDL3). Newborn plasma was characterized by a low amount of triglyceride-poor and cholesterol ester-rich VLDL and high content of HDL2 and HDL3. The VLDL and LDL concentrations increased drastically between 0 and 7 days together with the triglyceride content of the VLDL. At 30 days the lipid composition of VLDL was similar to that of adults, whereas the lipid/protein content remained low both in VLDL and LDL. The composition of HDL2 and HDL3 remained constant during this period, the percentage of HDL2 being higher in newborns than in adults. These compositional changes were reflected in the microviscosity of the lipoproteins, specially in the VLDL fraction.

Feline serum lipoproteins were fractionated into four distinct classes by density gradient ultracentrifugation and characterized with respect to physical and chemical properties. The distribution of serum lipids, lipoproteins and apolipoproteins was quite unlike that in man, the cat having five times as much high density lipoproteins (HDL) as low density lipoproteins (LDL). The lipoproteins in the d less than 1.019 g/ml fraction of cats were larger and were richer in triglycerides than their human counterparts and contained a considerable amount of beta-migrating particles. The low density lipoproteins of cats and man had similar chemical composition, but cat LDL had a higher negative charge, were smaller and contained apoprotein A-I. Cat HDL consisted of two distinct subfractions HDL2 and HDL3 with similar density boundaries and particle size as in man. In cat serum and HDL fraction apoprotein A-II was a minor component. Like human serum, fasting cat serum contained only the larger species of apoprotein B, apo B-100, whereas intestinal lymph contained exclusively the smaller apo B-48. Post heparin feline and human plasma possessed both lipoprotein lipase and hepatic lipase. Chylomicrons formed after a fat load in cats were removed from the circulation as rapidly as in man. It is concluded, that the cat is another animal model of potential interest for the study of lipoprotein metabolism.

(1) Male turkey serum contains two major lipoprotein families designated as LP-A and LP-B in its lipoprotein density classes. These two lipoprotein families were separated from each of the lipoprotein density classes by affinity chromatography on concanavalin A-Sepharose 4B. LP-A was present in the unretained and LP-B in the retained fractions. Both lipoprotein families were characterized by determination of their immunological and electrophoretic properties, the flotation coefficient and chemical composition. (2) LPb was distributed over a wider density range than LP-A. Seventy-four percent of LP-B was found in the LDL, 17% IN The VLDL and 8% in the HDL. In contrast, 98% of LP-A was present in the HDL and 2% in the LDL fractions: there were only trace amounts of LP-A in the VLDL. (3)Immunological and electrophoretic studies showed that the protein moiety of LP-A contained only the two non-identical A-I and A-II polypeptides of ApoA. The protein moiety of LP-B consisted only of ApoB. (4) Isolation of LP-A and LP-B from the major lipoprotein density classes provided further experimental evidence to confirm the existence of chemically distinct lipoprotein families as the fundamental physical-chemical entities of the serum lipoprotein system.

1. Different lipoprotein density fractions from pig serum were isolated by phosphotungstate precipitation followed by purification in the preparative ultra-centrifuge. 2. The protein part of very low density lipoproteins was composed of approximately 52 percent lipoprotein B apoprotein and the rest of lipoprotein C II apoprotein and other as yet unidentified peptides. 3. The protein moiety of low density lipoproteins consisted primarily of lipoprotein B apoprotein (over 95 percent); the amino acid compositions of lipoprotein B apoprotein of very low and low density lipoproteins were practically identical. 4. The predominant polypeptide of pig serum high density lipoproteins exhibited an amino acid composition and a molecular weight very similar to human liprotein A I apoprotein. In contrast to human lipoprotein A I apoprotein, the apoprotein from pigs was found to release leucine first followed by alanine, threonine, and lysine upon incubation with carboxypeptidase A. 5. In pig serum the major lipoprotein C apoprotein was found to be a polypeptide similar in amino acid composition to lipoprotein C II apoprotein from human serum. The molecular weight of this polypeptide is approximately 8000. Incubation experiments with carboxypeptidase A indicate serine to be the most likely C-terminal amino acid.

In order to study the degree and pathogenic aspects of the secondary hyperlipoproteinemia in patients under diuretic therapy we measured serum lipids, lipoproteins and the apoproteins A1, A2 and B in 12 adults after a 4 weeks placebo period and 6 weeks of treatment with chlorthalidon. There was a significant increase in atherogenic low density lipoproteins (LDL), (18%, P less than 0.05) whereas the high density lipoprotein-cholesterol Apo A1 and A2 levels were not significantly altered. The same was true for the total serum triglyceride- and the very low density lipoprotein- and LDL-triglyceride levels. The activity of lipoprotein lipase and hepatic triglyceride lipase was slightly but not significantly increased. A delayed LDL-catabolism seems to be the most probable pathogenic mechanism underlying the Chlorthalidon-induced hyperlipoproteinemia.

Serum lipoprotein and apoprotein concentrations were monitored for 24 weeks in 26 postmenopausal women treated with conjugated equine estrogens (0.625 mg/day) with the addition of dydrogesterone (10 mg/day) for the last 12 days of each 28 day cycle. The women had had no previous hormone replacement therapy. The estrogen plus dydrogesterone regimen caused significant (P less than 0.05) increases in triacylglycerol and HDL cholesterol concentrations. Both HDL2 and HDL3 cholesterol were increased. There were no other significant changes in lipoprotein concentrations. Both apoprotein AI and apoprotein AII concentrations increased significantly (P less than 0.05) over the study period. The ratios of apoprotein AI to apoprotein AII, apoprotein AI to HDL cholesterol and apoprotein AII to HDL cholesterol did not change. At the doses employed in this study, the use of dydrogesterone as a progestogen alters the effects of conjugated equine estrogens on lipoproteins and reinforces the view that the effects of a combined HRT regimen cannot be predicted from a consideration of the effects of the individual components.

The morphology and structural organisation of the complexes formed from the apoprotein of porcine high-density lipoprotein and dimyristoyl phosphatidylcholine (lecithin) have been studied using the technique of small-angle X-ray scattering. Scattering measurements made in solvents of varying electron density were interpreted in terms of a scattering-equivalent model for the structure of the complex. This model is described by an oblate ellipsoidal morphology with dimensions at 20 degrees C: major axis 11.0 nm, minor axis 5.5 nm. Within this overall shape the lipid hydrocarbon chains are organised in an apolar core whilst the lipid polar head groups and protein are located in a outer shell 0.85 nm in thickness. The oblate morphology demonstrates that the structure of the complex is directed by the fundamental bilayer organisation of the lecithin. The dimension of the minor axis (5.5 nm) indicates that phospholipid hydrocarbon chains are orientated perpendicular to the interface.

Quantitation of the apoprotein constituents of lipoproteins has extended our knowledge of plasma lipid transport. Previously, B protein content of low density lipoprotein could be measured by radial immunodiffusion only after ultracentrifugation. However, if performed in 1.5% agarose gel with standards and measured at 18 hr rather than at equilibrium, low density lipoprotein B protein can be measured directly in plasma, eliminating the need to separate very low density lipoprotein.

The apolipoprotein A concentration in the plasma of ten healthy human subjects was measured immunologically on three occasions at monthly intervals and the following results recorded. 1. There was no difference between fasting and non-fasting apoprotein A concentrations. 2. Apoliportein A levels were higher in females than in males (p less than 0.001). 3. The correlation coefficient calculated for high density lipoprotein cholesterol and apolipoprotein A was 0.62. 4. The apoprotein values varied widely between subjects and ther were considerable concentration differences from month to month in the plasma of each individual.

Two electrophoretic populations of very low density lipoprotein are frequently observed in both normal and hyperlipidemic human sera. This gives the appearance of two pre-beta bands, called the "double pre-beta lipoprotein phenomenon." The slow and fast bands forming the double pre-beta lipoprotein were isolated by ultracentrifugation in the zonal rotor under rate flotation conditions. On the basis of the effluent position, the slow band showed a lower flotation coefficient than the fast one. The lipid and apoprotein composition of the two very low density lipoprotein populations isolated by zonal ultracentrifugation was in close agreement with those obtained by preparative agarose gel electrophoresis. The slow and fast pre-beta fractions had the same triglyceride fatty acid composition. Both fractions contained only higher molecular weight apo B-100, while the slow fraction was relatively enriched in apo E and apo C-III. Since the slow pre-beta fraction showed the typical properties of the remnant particle, studying this fraction could clarify the possible relationship between remnant lipoproteins and atherogenesis. Zonal rotor ultracentrifugation may be useful to characterize remnant particles in normal and hyperlipidemic subjects.

Acute biliary obstruction in the rat is associated with striking alterations of the plasma level and the physico-chemical properties of plasma lipoproteins. 1. The level of very low density lipproteins (VLDL) in plasma increases from 2 to 3 fold. The chemical composition of VLDL is characterized by a high content of phospholipids and cholesterol and by a diminution of the relative content of triacylglycerols and protein. On cellulose acetate electrophoresis, VLDL show a beta-mobility. 2. The plasma concentration of low density lipoproteins (1.019--1.063 g/ml, LDL2) increases several fold above the control level. Phospholipids and unesterified cholesterol are the major components of this fraction which contains only a minute amount of cholesteryl ester (4%) and triacylglycerols (10%). LDL2 contain a component which migrates to the cathode in 1% agar gel electrophoresis. Separation of LDL2 by gel filtration on 2% agarose column results in the identification of three subfractions. Subfraction I contains a large proportion of cholesterol and triacylgylcerols, subfraction II is rich in unesterified cholesterol and phospholipids whereas subfraction III has a chemical composition fairly similar to that of the control LDL2. 3. The level of high density lipoproteins (HDL) also increases after bile duct ligation. The chemical composition of HDL2 (1.063-1.125 g/ml) is characterized by a high content of unesterified cholesterol and phospholipids and by a remarkable reduction in the content of cholesteryl esters and protein.

The effects of propranolol and prazosin on plasma lipoproteins in patients with essential hypertension were evaluated according to a crossover protocol of two 8-week periods with a washout of 4 to 6 weeks. Eleven patients with moderate hypertension (greater than 90 but less than or equal to 144 mm Hg, diastolic) and slightly overweight (+10% to +/- +30%, according to Metropolitan Life Insurance tables) were selected. No dietary changes were prescribed. Plasma cholesterol, triglycerides (TG), and lipoprotein changes were monitored at the beginning of each sequence and at 2-, 4- and 8-week intervals. Prazosin, when given first, did not essentially modify any of the metabolic parameters, except for a slight elevation in plasma apoprotein AI levels, i.e., the main protein component of high density lipoprotein (HDL); propranolol caused a significant rise in total TG and very low density lipoprotein TG (VLDL-TG) levels (+37.3% and +23.9%, respectively). Somewhat lower total TG (+19.6%) and vLDL (17.8%) TG elevations were noted when propranolol was given first; plasma glucose was also significantly raised (+12.8%). Triglyceride and glucose levels returned to normal upon changing to prazosin. Total plasma- and lipoprotein-associated cholesterol levels were essentially unchanged with either drug; similarly, no significant changes were detected in total plasma apoprotein B (the main protein component of LDL and also VLDL), a component of apoprotein AI levels. Uric acid levels were slightly raised on propranolol. There was an 8.8% reduction in uric acid levels when the medication changed from propranolol to prazosin.

Serum cholesterol (TC), Triglycerides (TG), high density lipoprotein (HDL) cholesterol and the apoproteins A1 and B were determined in 20 males survivors of myocardial infarction and in 20 healthy age and sex matched controls. HDL-C, HDL-C/TC and apo B/apo A1 were significantly different between the two groups. In a multivariate statistical analysis 85% of all subjects were correctly classified by using the HDL-C/TC and the apo B/apo A1 ratio. This study indicates that the apoproteins quantification yield complementary information in discriminating young male myocardial infarct survivors from normal controls.

There was a rapid transfer of radioactive peptides to other lipoprotein fractions during the first 30 min after the intravenous injection of 125I-labeled rat very low density lipoprotein (VLDL) into rats. After this initial redistribution of radioactivity, label disappeared slowly from all lipoprotein fractions. The disappearance of 125I-labeled human VLDL injected into rats was the same as that of rat VLDL. Most of the radioactivity transferred from VLDL to low density (LDL) and high density (HDL) lipoproteins was associated with two peptides, identified in these studies by polyacrylamide gel electrophoresis as zone IVa and IVb peptides (fast-migrating peptides, possibly analogous to some human C apolipoproteins), although radioactivity initially associated with zone I (analogous to human apolipoprotein B) and zone III (not characterized) was also transferred to LDL and HDL. That the transfer of label from VLDL to LDL and HDL primarily involved small molecular weight peptides was confirmed in studies using VLDL predominantly labeled in these peptides by in vitro transfer from 125I-labeled HDL. Both zone I and zone IV radioactivity was rapidly removed from VLDL during the first 5 min after injection. However, although most of the zone IV radioactivity was recovered in LDL and HDL, only 12% of the label lost from zone I of VLDL was recovered in other lipoproteins, with the remainder presumably having been cleared from the plasma compartment. We have concluded that, during catabolism of rat VLDL apoprotein, there is a rapid transfer of small molecular weight peptides to both LDL and HDL. During the catabolic process, most of the VLDL is rapidly removed from the circulation, with only a small portion being transformed into LDL molecules.

Plasma lipid values studied in 30 subjects with stroke at days 1, 2 and 4 of the early phase indicated a significant decrease in total cholesterol, HDL-cholesterol and apolipoprotein A1 from day 1 to 4. However, there was no significant difference between values at day 1 and during the 4th month of convalescence. Since some patients admitted to hospital are never followed up later in a hospital environment, it would seem advisable, for practical purposes, to perform plasma lipid analysis on the first day of admission.

In a double blind study 27 patients with type II hyperlipidemia (8 IIa and 19 IIb) were treated as follows: 13 received placebo and 14 sn-polyenylphosphatidylcholin (PPC) (P 0206/1/01, Nattermann GmbH, Cologne) in a dose of three times 450 mg b.i.d. In all patients, and also in the two subclasses of patients with type IIa and type IIb hyperlipidemia, total cholesterol and LDL cholesterol were lowered significantly by PPC. The other parameters showed only minor variation. There was a downward trend in apoprotein B, triglycerides and VLDL cholesterol, and an upward trend in apoprotein AI, with virtually unchanged HDL cholesterol. None of these variations was significant compared with placebo. The fall in LDL cholesterol with unchanged HDL cholesterol caused a statistically significant decrease in the LDL cholesterol/HDL cholesterol ratio, thus supporting the hypothesis of an antiatherogenic property of PPC, as demonstrated experimentally in various animals.

In a study of lipoprotein subclasses in 79 healthy members of sixteen nuclear families evidence was obtained that low-density-lipoprotein (LDL) subclass patterns determined by gradient-gel electrophoresis are influenced by a common allele at a single genetic locus. The estimated frequency of the allele leading to the phenotype characterised by predominance of small, dense LDL subclasses was about 15%. Expression of this phenotype appears to be age dependent, in that most affected subjects in this population were older than 40 years. Although plasma lipid levels were normal in most subjects with this trait, levels of plasma apoprotein B and triglyceride were higher and levels of apoprotein AI and HDL2 lower than in unaffected family members. It is possible that this genetic trait may interact with other genetic or environmental variables in predisposing affected individuals to atherogenic lipoprotein and apoprotein profiles.

Some properties of very low density lipoproteins were studied under conditions causing an increase of their concentration in blood plasma. Content of high molecular apolipoprotein B and low molecular lipoproteins were estimated after fractionation using column chromatography and selective precipitation with tetramethylurea. In 216 men (40-59 years old) with hypertriglyceridemia the increase in content of particles of very low density lipoproteins was accompanied by simultaneous alteration in their composition in blood plasma: content of low molecular polypeptides, triglycerides and cholesterol was increased per a weight unit of apoprotein B. At the same time, the absolute concent of apoprotein B and of low molecular apoproteins of very low density lipoproteins was increased in blood plasma. The most distinct alteration in the ratio of apolipoproteins to very low density lipoproteins was observed, if content of testosterone--activator of lipoprotein lipase--was decreased in blood plasma.

The siblings presented here are the third family found in Japan with familial LCAT deficiency. Their post-heparin plasma lipoprotein lipase and hepatic triglyceride lipase activities were measured selectively by an immunochemical method. Plasma triglyceride levels were elevated, and post-heparin plasma lipoprotein lipase was decreased only in a patient with nephropathy, while hepatic triglyceride lipase activities were within reference limits in both patients. The plasma concentrations of apo A-I, apo A-II, and apo B were reduced in both patients. On the other hand, the plasma concentration of apo E was markedly increased. Enzyme replacement therapy by plasma transfusion in the propositus resulted in marked improvement of deranged compositions of triglyceride-rich lipoproteins. Also, improvement of the plasma apo E concentration was demonstrated, while the improvement of post-heparin lipase did not occur. These results suggest that LCAT may play an important physiological role in triglyceride metabolism as well as in cholesterol metabolism.

The effect of procetofen (fenofibrate) on lipids and apoproteins was studied in ten patients affected with familial type II-A and II-B hyperlipoproteinemia. Following stabilization with an isocaloric diet for 2 months, the patients were given 300 mg/day of procetofen for 3 months, then placebo for 1 month. Plasma cholesterol and triglycerides were decreased by 15% and 46%, respectively. Plasma apo B was lowered by 17%. The predominant decrease in lipids and apoproteins occurred in VLDL, whereas in HDL cholesterol increased significantly but not its major apoprotein, apo A-I. A mechanism of action involving increased catabolism of VLDL and reduced synthesis of LDL and VLDL is proposed.

The lipoproteins from two sibs with familial lecithin-cholesterol-acyltransferase(LCAT)-deficiency were further characterized. Comparatively lipoproteins from patients with secondary LCAT-deficiency were studied. Both groups of patients had particles of unusual size and shape in the alpha1-(HD-2)-lipoprotein subfraction. The abnormal HDL-2 particles were disk-like in appearance with a major axis of about 180 A and a minor axis of about 40 A and tended to aggregate into long coinlike stacks. The abnormal HDL-2 particles contained the normal protein constituents of HDL Apo A-I, Apo A-II and Apo C but in addition a major polypeptide with a M.W. of 39000 not seen in significant amounts in normal high-density-lipoproteins. This polypeptide was found identical in size, isoelectric focusing and immunochemically with an arginine-rich normal polypeptide constituent of very-low-density-lipoproteins designated apoprotein E. Presence of this protein marker in the HDL allowed the specific immunological detection of the abnormal HDL-2 (LP-E) in plasma. Further minor biochemical abnormalities were observed in the lipoproteins of the patients with familial LCAT-deficiency. However, the main protein constituents of their HDL, the Apo A, Apo C and Apo E polypeptides, were found to be identical electrophoretically and by analytical isoelectric focusing with their normal counterparts. The data suggest that the basic genetic defect in the hereditary disease leads to a deficient activity of the LCAT-enzyme and that all abnormalities in the lipoprotein spectrum are secondary.

Cholesterol-induced density lipoprotein(s), termed HDLc, is one of the abnormal lipoproteins which occur in experimental hypercholesterolemia in several animal species, including rats. Thus far, HDLc has been exclusively isolated by sequential ultracentrifugation followed by Geon-Pevikon block electrophoresis, which is time-consuming and requires some specialized knowledge. In this report, a faster and more convenient alternative method for the isolation of HDLc is described. A combination of a single ultracentrifugation and agarose gel chromatography followed by concanavalin A-Sepharose affinity chromatography was employed. HDLc thus obtained was similar to and probably identical with the HDLc isolated by Geon-Pevikon electrophoresis, with respect to chemical composition, electrophoretic properties in agarose gel, apoprotein patterns in SDS polyacrylamide gel electrophoresis, and electron micrographic appearance.

To study the effect of lecithin: cholesterol acyltransferase (LCAT) on the plasma lipoproteins of patients with familial LCAT deficiency, whole plasma or the lipoprotein fraction of d smaller than 1.006 g/ml (VLDL) was incubated in the presence of LCAT and subsequently examined by chemical, physical, and immunological techniques. The following occured upon incubating either hyperlipemic or nonlipemic plasma: The concentrations of polar lipids decreased, particulary in the large molecular weight lipoprotein subfraction of d 1.019-1.063 g/ml (LDL2) and in the lipoprotein fraction of 1.06301.25 g/ml (HDL). The concentration of cholesteryl ester (CE) increased, particularly in the VLDL and in the lipoprotein fractions of d 1.006-1.019 g/ml (LDL1) and LDL2. The concentration of arginine-rich apolipoprotein decreased in the HDL and increased in the VLDL and LDL1. The concentrations of the C-apoliproteins appeared to change in the opposite direction. The concentration of apolipoprotein B in the LDL increased concomitantly with an increase in the concentration and flotation rsate of the small LDL2. The concentration apolipoprotein A-I in the HDL increased; and a major component in the HDL fraction became identical in apperance to normal HDL. Upon incubating a patient's isolated VLDL in the presence of LCAT, lipoproteins with properties similar to normal LDL2 were formed. These experiments show that the LCAT reaction can alter the apolipoprotein content and physical properties as well as the lipid content of the patient's lipoproteins.

Composition of major plasma lipoproteins was studied in 14 normal women during different phases of the menstrual cycle for three consecutive months. The results were compared to measurements in ten normal age-matched men for a comparable period, to delineate possible sex differences in lipoprotein metabolism in young adults. Blood samples were obtained every 3--5 days after a 14-hr overnight fast and processed for determinations of total plasma cholesterol, LDL- and HDL-cholesterol, and apoproteins B and A-1. In premenopausal women, a significant, 10%--25% cyclical suppression of total plasma cholesterol, LDL-Chol, and LDL-apoB occurred during the luteal phase, which was significantly lower than unchanging concentrations found in men at any time interval. HDL-Chol remained in a significantly higher fixed concentration range in the female subjects as compared to the men. These sex differences in lipoprotein metabolism may have relevance to the reduced susceptibility of premenopausal women to atherosclerosis.

Serum cholesterol, HDL cholesterol (HDL-C), and apoproteins, A1, A2 and B were determined in 70 male survivors of myocardial infarction and in an equal number of healthy controls, matched for age, sex and body mass index. In univariate analyses, the Apo B/Apo A1 ratio discriminated the best between cases and controls, giving a 72% exact classification. In a multivariate analysis, the Apo B/Apo A1 ratio, HDL-C and the Apo A2/Apo A1 ratio contributed independently to the discrimination of cases from controls while the overall exact classification was 82%. These promising results were comparable in younger and older subgroups. Thus, the determination of apoproteins yielded complementary information in this cross-sectional survey and warrants further study in a prospective setting.

Serum apoprotein and lipid concentrations were measured in 63 patients undergoing coronary angiography. Thirty-eight patients had 50% or higher grade stenoses, 25 had chest pain, but no significant stenoses. Among the patients with higher grade stenoses 71% had hyperlipoproteinemias as opposed to 12% in patients without stenoses. As compared to suitable normal controls, patients with angiographically documented coronary heart disease showed significant changes in all lipid and apoprotein concentrations under study. However, differences between the two patients groups were also noted. Among these, apo A-I, A-II and B, total cholesterol and LDL cholesterol were statistically significant. These results indicate that apoprotein A and B levels, total cholesterol and LDL cholesterol are good discriminators of the severity of coronary heart disease, while HDL cholesterol is a more suitable parameter for epidemiological studies.

Since accelerated atherosclerosis may be induced by excess circulating remnants of triglyceride-rich lipoprotein catabolism, we looked for evidence of remnant particle accumulation in the lipoproteins of 11 patients on long-term dialysis. We found several abnormalities in lipoprotein protein and lipids: enrichment of intermediate-density lipoproteins (ILD) and low-density lipoproteins (LDL) with triglyceride; the presence of apoprotein B48 (a "marker" for intestinal lipoproteins) in very-low-density lipoproteins (VLDL); an increased concentration of apoprotein AIV (a protein related to chylomicron transport); the presence of AIV in VLDL, IDL, and LDL; and the presence in LDL of apoproteins C and E (proteins not normally found in LDL). These findings strongly suggest accumulation of remnants of triglyceride-rich lipoproteins in patients with chronic renal failure who are undergoing peritoneal dialysis or hemodialysis, and may explain in part the increased incidence of coronary deaths among these patients.

The relationship between macrovascular disease and serum lipids, low density lipoprotein (LDL) cholesterol, high density lipoprotein (HDL), and subfraction cholesterol, and apolipoproteins has been examined in 53 female and 95 male patients with non-insulin-dependent diabetes mellitus (NIDDM). In males, those with macrovascular disease had higher serum and LDL cholesterol concentrations than those without. In females, those with macrovascular disease had higher levels of serum triglyceride, cholesterol, LDL cholesterol, as well as lower HDL, HDL2, and HDL3 cholesterol and apoprotein A-1, than those without. On multivariate analysis, LDL cholesterol was the most important association with macrovascular disease in males and apoprotein A-1 in females. In a subgroup of 36 patients, a double-blind placebo controlled study using bezafibrate or placebo, in addition to conventional oral hypoglycaemic therapy over 4 months, showed falls in serum and LDL cholesterol and in serum triglyceride and a rise in HDL cholesterol in the treated group. These changes should reduce the incidence of macrovascular disease in NIDDM and we suggest further prospective studies of such therapy in addition to conventional oral hypoglycaemic agents.

The major apoprotein of high density lipoprotein is apolipoprotein A-I (ApoA-I). In addition to being a structural component of this class of lipoproteins, ApoA-I also has a physiologic role as an activator of lecithin-cholesterol acyl transferase, an enzyme important in the metabolism of all lipoproteins. To measure ApoA-I content in human plasma, to assess its immunologic activity in hyperlipoproteinemia, and to carry out certain structural studies of high density lipoproteins, we have developed a double antibody radioimmunoassay. ApoA-I, isolated by gel filtration, was used to produce monospecific antisera. ApoA-I was iodinated by chloramine-T and the resulting [(125)I]-ApoA-I was purified by gel filtration. > 85% of [(125)I]-ApoA-I was precipitated by antibody, and 90% of bound [(125)I]ApoA-I was displaced by "cold" ApoA-I. Other lipoproteins and apoproteins did not react. Plasma and high density lipoprotein from normals and subjects with hyperlipoproteinemia displaced counts in parallel with ApoA-I, suggesting that the same antigenic determinants were reacting with antibody on lipid-free and lipid-associated ApoA-I. However, less than 5% of ApoA-I of high density lipoprotein reacted in the assay. Removal of the lipid by extraction increased the reactivity of ApoA-I in high density lipoprotein 15-20-fold; thus more than 95% of the ApoA-I molecules in "intact" high density lipoprotein are unreactive with antibody. Normal and hyperlipoproteinemic plasma and high density lipoproteins isolated from the same subjects continued to display parallelism with ApoA-I standard after lipid extraction, suggesting that ApoA-I of normal and hyperliproteinemic subjects are immunologically identical. About 90% of ApoA-I was in the d 1.063-1.21 fractions of normal plasma, trace quantities were found in the lipoproteins of d < 1.063, and the rest (about 10%) was in the d > 1.21 fraction. Normal plasma levels, assessed in extracted plasmas with a precision of 8%, were 100+/-35 mg/dl. Levels were normal in small groups of subjects with types II and IV hyperlipoproteinemia and high in pregnancy. However, larger population studies need to be performed to determine the distribution of ApoA-I levels in the various hyperlipoproteinemias.

The localization patterns of human plasma lipoproteins and their respective apoproteins and of neutral lipid were determined in normal and atherosclerotic arteries. Specific antisera were prepared against plasma low-density lipoproteins(LDL) and their apoproteins (apoB), high-density lipoproteins(HDL) and one of their major apoproteins (apoA-I1, and apoC-III, which is a major apoprotein of very low-density lipoproteins (VLDL). Using immunofluorescence techniques, the various antigens were localized in arterial samples obtained at surgery or autopsy. The three apoproteins and neutral lipid were localized to the same tissue areas, namely, lipid core regions and certain connective tissue of atherosclerotic lesions, in 61% of the fibrous plaques and 48% of the fatty streaks examined. In marked contrast, none of the uninvolved arterial regions showed the presence of all four factors together. As controls, the localization of other serum proteins was also determined in these arteries using immunofluorescence techniques. Fibrinogen was associated with regions of maximum complementary localization of factors in 37% of the fibrous plaques and 64% of the fatty streaks. However, albumin was found in only 4-5% of these same regions. The present results suggest that not only LDL but also HDL and VLDL or their respective apoproteins as well as fibrinogen are specifically retained by certain tissue components of the atherosclerotic lesion.

We evaluated the long-term effects of indapamide, a non-thiazide diuretic, on blood pressure, glucoregulation, free insulin and C-peptide levels, and lipoprotein and apoprotein metabolism in 13 hypertensive diabetic patients for 24 weeks. Indapamide significantly reduced both systolic and diastolic blood pressure by 15% and 17%, respectively. Both mean fasting serum glucose and integrated glucose responses after oral glucose load (75 g) were significantly higher during indapamide therapy than at week 0. The mean fasting and stimulated C-peptide responses were significantly increased despite worsening glucose control. At the end of 24 weeks, mean glycosylated hemoglobin level had increased significantly. Indapamide caused a slight but insignificant rise in the total triglyceride, cholesterol, and low-density lipoprotein cholesterol levels, while the high-density lipoprotein cholesterol level decreased. In addition, the apoprotein A-1 concentrations remained unchanged while the apoprotein B-100 level decreased. Apart from hypokalemia (less than 3.5 mEq/L [less than 3.5 mmol/L]) in three patients that required oral potassium supplementation, biochemical changes were of no clinical consequence.

The clinical presentation and course of abetalipoproteinemia in two male patients, a child and an adult, are described. Apoprotein B was absent in both cases and each patient had > 50% acanthocytes present on peripheral blood smear. Family studies revealed normal lipid profiles in the parents of both patients, which is consistent with the usual autosomal recessive inheritance of this disorder. In addition to a low-fat diet, both patients have been maintained on high doses of vitamins A and E. In the adult patient, detailed evaluations over a five-year period have failed to show any progression of neurological disease while maintained on high-dose vitamins. The role of supplemental vitamins A and E in the therapy of abetalipoprotenemia is discussed.

The effects of C1-719 on plasma lipid and lipoprotein concentrations have been examined in four patients with endogenous hypertriglyceridaemia maintained on an isocaloric diet for a period of 6 months. During therapy (400 mg/day) the mean plasma triglyceride and cholesterol concentrations were reduced by 35% and 15% respectively, while the administration of 800 mg/day reduced these by 49% and 31%. This hypolipidaemic effect was due to a reduction in the circulating level of very low density lipoproteins (VLDL) without a change in their composition. Before treatment the plasma VLDL triglyceride turnover, and FFA flux, were higher than that of normal subjects maintained on a similar diet. The plasma VLDL B-apoprotein turnover was similarly higher than in the controls. Administration of C1-719 decreased the plasma VLDL triglyceride turnover, FFA flux and VLDL B-approtein turnover. The drug reduced the insulin response following a glucose load with some decrease in glucose levels. The results suggest that the increase in plasma triglyceride concentration in patients with endogenous hypertriglyceridaemia is due to increased production of plasma VLDL triglyceride and its apoptein associated with an enhanced supply of FFA for hepatic triglyceride synthesis. C1-719 exerts a hypolipidaemic effect through a reduction of VLDL production, consequent upon inhibition of lipolysis as well as decreased synthesis of the apoprotein carrier. These effects could in part be explained by an improvement in peripheral tissue responsiveness to insulin and decreased exposure of the liver to high levels of insulin. However, a direct effect of the drug on adipose tissue and liver metabolism has to be considered.