Immunoaffinity fractionation of high-density lipoprotein subclasses 2 and 3 using anti-apolipoprotein A-I and A-II immunosorbent gels.

High-density lipoprotein (HDL) subclasses 2 and 3 prepared by density gradient ultracentrifugation have been further fractionated by immunoaffinity chromatography using antibody affinity gels targetting the major HDL apolipoproteins, A-I and A-II. Fractions containing A-I without A-II (AI w/o AII) and A-I with A-II (AI w AII) were isolated from both density ranges. Whereas there were similar concentrations of the major subfraction (HDL3(AI w AII] in both males and females, the remaining subfractions were present in higher concentrations in females as compared to males, in the order HDL3 (AI w/o AII) less than HDL2(AI w AII) less than HDL2(AI w/o AII). The difference was most marked for HDL2 (AI w/o AII), where plasma concentrations in females were almost 3-fold greater than in males. Compositional analyses indicated that the plasma concentrations of the fractions, rather than their compositions, were the major determinants of male-female differences in HDL levels. In contrast, fractions defined by similar apolipoprotein criteria and isolated from different density subclasses (i.e., HDL2(AI w/o AII) vs. HDL3(AI w/o AII) and HDL2(AI w AII) vs. HDL3(AI w AII] showed major compositional differences. This is suggestive of distinct lipoprotein particles.

Characterization of subpopulations of lipoprotein particles isolated from human cerebrospinal fluid.

The aim of the present study was to define lipoprotein complexes within cerebrospinal fluid (CSF) in terms of their apolipoprotein composition, using fractionation procedures considered optimal for maintaining lipoprotein structural integrity. Five apolipoproteins were identified, namely apolipoproteins A-I, A-IV, D, E and J. These were differentially distributed amongst lipoprotein particles of which three major subpopulations were identified. CSF-LpAI (20.1 +/- 3.8 nm) was enriched in apolipoprotein A-I and contained the major proportion (> 50%) of apolipoproteins D, E and J. CSF-LpE, of similar size to CSF-LpAI (20.2 +/- 3.1 nm), was composed principally of apolipoprotein E, with minor quantities of apolipoproteins A-I, A-IV, D and J. Elimination of these particles from cerebrospinal fluid by immunoabsorption revealed a third subpopulation of significantly greater diameter (32.0 +/- 6.8 nm). The majority (62%) of apolipoprotein A-IV was also present in this fraction. The study demonstrates the structural and size heterogeneity of lipoproteins in cerebrospinal fluid. This may reflect the lipid transport processes within the central nervous system.

Distribution of apolipoprotein E between free and A-II complexed forms in very-low- and high-density lipoproteins: functional implications.

The stability of apolipoprotein E/lipoprotein associations has been examined as a function of apolipoprotein E phenotype. Visualisation by immunoblotting showed plasma apolipoprotein E to be present in two forms; the free form and, as previously described, an E-A-II complex. In very low density lipoproteins isolated by gel filtration from subjects with E3/3 and E4/3 phenotypes, apolipoprotein E was present essentially in the free form (ratio free: complex of 12.2 and 37.5, respectively). Exploiting ultracentrifugation as the disruptive agent, very-low-density lipoproteins thus isolated were shown to have substantially lower ratios (5.6 and 5.4, respectively) reflecting preferential loss of free apolipoprotein E. In high-density lipoproteins isolated by gel filtration from E3/3 phenotypes, apolipoprotein E was largely present as an E-A-II complex (80.3%). In contrast, the majority of apolipoprotein E in high-density lipoproteins from E4/3 phenotypes was present in the free form (58.7%). In both phenotypes, the content of free apolipoprotein E was markedly reduced by ultracentrifugation. The results confirm the notion that the formation of the E-A-II complex is a major determinant of the stability of apolipoprotein E-high-density lipoprotein associations. Moreover, that the predominant, ancestral isoform, apolipoprotein E3, exists largely as an E-A-II complex in higher density lipoproteins has important functional implications for this plasma source of apolipoprotein E.

A novel high-density lipoprotein particle and associated protein in rat plasma.

This report describes the characterization of a novel rat apolipoprotein, which, as partial sequencing suggests, does not correspond to any described protein. The protein (termed PX) has an estimated molecular mass of 19.5 kDa and pI in the range 5.5-5.8. Monoclonal antibodies were obtained against protein PX and results on distribution among rat lipoproteins show it to be associated mainly with high-density lipoproteins (HDL), but also with VLDL. Immunoaffinity chromatography of total HDL shows protein PX to be included in a distinct lipoprotein particle, particularly enriched in free cholesterol, with which only traces of other apolipoproteins are associated. Immunologically crossreacting entities are found in the plasma of several species, including man. Retention of the epitope carried by the protein PX would suggest that it is of particular structural or functional importance. It remains to be established whether its function is associated with lipid metabolism.

Differences in lipoprotein subfraction composition and distribution between type I diabetic men and control subjects.

Subfractions of very-low-density and low-density lipoproteins were examined in 10 male normolipidemic type I (insulin-dependent) diabetic patients before and after improvement of metabolic control and were compared with subfractions from male control subjects matched to the diabetic patients at entry for age, body mass index, plasma cholesterol, and plasma triglycerides. Two consistent differences in subfraction composition were noted between the diabetic patients at entry and the control subjects. First, subfractions from diabetic patients tended to be cholesterol-ester poor and triglyceride rich; this was particularly marked for the low-density lipoprotein subfractions. Second, the subfractions from pretreatment diabetic patients contained higher proportions of non-apolipoprotein B apolipoproteins. This compositional anomaly, but not the lipid modifications, responded to but was not completely normalized by improved glycemic control, which was also accompanied by reductions in the plasma concentrations of all subfractions. Treatment modified subfraction distribution so that the lipoprotein profile of posttreatment diabetic patients more closely resembled the profile observed in the control subjects. These changes were achieved without significant modification of daily insulin dose. In the context of blood lipid risk factors, the results argue for the need to maintain optimal insulinization even in apparently normolipidemic diabetic patients to avoid modifications of the lipoprotein pattern toward a potentially more atherogenic profile.

Apolipoprotein E polymorphism as a risk factor for vascular disease in diabetic patients.

OBJECTIVE: To examine the prevalence of cardiovascular disease in diabetic patients as a function of apolipoprotein (apo) E polymorphism. RESEARCH DESIGN AND METHODS: The apo E phenotypes and plasma lipid, lipoprotein, and apo levels were determined for 517 Italian diabetic patients. The prevalence of cardiovascular disease (defined as ischemic heart disease [HD] and/or peripheral vascular disease and/or cerebrovascular disease) was assessed as a function of apo E polymorphism at entry and after 4 years. RESULTS: The occurrence of vascular disease did not differ significantly between diabetic patients in the various categories of apo E phenotype either at entry into the study or after 4 years. When expressed as a percentage of patients with disease, we observed--for E2, E3, and E4 carriers, respectively--at entry: IHD, 20.0% (n = 14), 21.0% (n = 79), and 21.5% (n = 14); and macroangiopathy, 24.3% (n = 17), 29.3% (n = 110), and 24.6% (n = 16). Apo E polymorphism did not make a significant contribution to multiple logistic regression models designed to identify the factors associated with the occurrence of vascular disease in diabetic patients. CONCLUSION: Apo E polymorphism and, notably, the apo E4 allele cannot be universally considered as a particular risk factor for cardiovascular disease in diabetic patients.

Metabolic effects of dietary fiber from dehulled soybeans in humans.

The normal diet of six healthy volunteers was supplemented by 21 g of dietary fiber from two different soybean seed fiber preparations, either a nonpurified and never-dried soya pulp A (39% dietary fiber) or a purified soya fiber B (79%), for 3 wk each. Mean daily fecal wet weight was increased by 19 and 38% in the fiber periods A and B as compared to a 2-wk control period (p less than 0.05). Stool frequency and transit time remained unchanged. Fecal fiber increased by 52% only during period B. Fecal calcium, magnesium, and iron were increased (p less than 0.05), mainly after higher intakes during both fiber periods. Excretion of neutral steroids remained unchanged, but their concentration was lowered (p less than 0.05). A 21% increase of fecal bile acids by fiber A was specifically due to deoxycholic acid (+32%, p less than 0.01). Oral glucose tolerance was slightly improved after period B. Neither fiber changed serum triglycerides, but fiber B increased low-density lipoprotein-cholesterol by 19% (p less than 0.01) and low-density lipoprotein-phospholipids by 16% (p less than 0.05). The ratio high-density/low-density lipoprotein-cholesterol, however, did not change significantly. Thus, dietary fibers from soybean do not seem to contribute to the hypocholesterolemic effect of soya. The results of this study also demonstrate that two apparently similar dietary fibers, coming from a single source, can exert distinctly different metabolic effects.

Immunofractionation of high density lipoprotein subclasses 2 and 3. Similarities and differences of fractions isolated from male and female populations.

High density lipoprotein (HDL) subclasses 2 and 3 isolated from male and female populations were further subfractionated by immunoaffinity techniques. Each subclass gave rise to 2 fractions: one contained apolipoprotein (apo) A-I but no apo A-II (LpAI); the other contained apo A-I and apo A-II (LpAI,AII). The bulk fraction (HDL-3(LpAI,AII)) comprised over 70% of total HDL and was present in similar concentrations in both populations. There were, however, significant male-female differences in plasma levels of the minor HDL-3 fraction i.e. HDL-3(LpAI). Females had significantly higher plasma concentrations of both fractions within HDL-2. These fractions also exhibited strong, positive correlations with total HDL cholesterol concentrations, both in males as well as females. It suggests that metabolic activities giving rise to both HDL-2(LpAI) and HDL-2(LpAI,AII) determine plasma HDL cholesterol concentrations. Several similarities were noted between the male and female populations. Triglyceridaemia was negatively correlated with HDL-2 derived fractions and positively correlated with the bulk fraction HDL-3(LpAI,AII). Compositional data showed that the fraction (LpAI) had a lower esterified cholesterol to total cholesterol ratio than the fraction (LpAI,AII), the differences being more apparent at the HDL-3 level. Additionally, analysis of the surface components of HDL-3 fractions suggested that (LpAI,AII) had a greater potential than (LpAI) for absorbing lipoprotein surface material. Finally, the relative concentrations of the individual components of fractions within the same population and defined by the same apolipoprotein criterion showed highly significantly, positive correlations. Such correlations were not apparent for apolipoprotein dissimilar fractions. These observations could reflect a metabolic link between apolipoprotein similar fractions.

HDL lipids in close relatives of coronary heart disease patients. Environmental and genetic influences.

Female first-degree relatives of CHD patients differed, after the age of forty, from the normal control population by their low HDL cholesterol. Between the ages of 20 and 40 years a slight but significant increase in HDL triglycerides was observed. Except for hormonal contraception which induces significant lowering of HDL cholesterol in the first degree relatives, the observed differences in HDL lipids did not seem related to environmental factors but rather to be genetically determined. In contrast, the low HDL cholesterol observed in the wives of the CHD patients appeared to be related to differences in alcohol intake.

Apoprotein D in a healthy, male population and in male myocardial infarction patients and their male, first-degree relatives.

This report examines the correlation of serum apoprotein D with other lipoprotein lipids and apoproteins in a healthy, male population and compares the levels of high density lipoprotein apoprotein D of this control population with 2 samples composed of male, acute myocardial infarction patients and their healthy, male, first-degree relatives. Highly significant correlations were observed with very low density lipoprotein lipids (negative), high density lipoprotein lipids (positive) and serum triglycerides (negative). Serum and low density lipoprotein apoprotein B was not correlated with serum apoprotein D, whereas apoprotein A-I from serum and high density lipoproteins was strongly correlated with apoprotein D. A significant reduction in high density lipoprotein apoprotein D was observed in male, myocardial infarction patients. Their male, first-degree relatives also had lower apoprotein D levels, but the difference was not significant.

High density lipoprotein (HDL) subfractions in cardiovascular patients with low levels of HDL-cholesterol. Influence of hypertriglyceridaemia on subfraction concentration and composition.

The major high density lipoprotein (HDL) subfractions were examined in angiographically defined cardiovascular patients with low HDL-cholesterol (HDL-C) levels. The aims were to study subfraction concentration and composition, and the extent to which hypertriglyceridaemia (HTG) modified these variables. Normotriglyceridaemic (NTG)-low HDL-C patients showed similar subfraction composition to age-matched healthy controls. However, these groups showed notable differences in subfraction composition compared to HTG-low HDL-C patients, particularly with regard to the HDL2 subfraction. HDL subfraction mass was significantly reduced in both cardiovascular groups; the HTG group showed a greater reduction in HDL2, whilst the NTG group showed a greater reduction in HDL3. The major HDL apoprotein (apo A-I) was lower in both subfractions of the cardiovascular patients. Apo A-II showed significant reductions only in the HTG patients.

High density lipoprotein cholesterol in male relatives of patients with coronary heart disease.

To study factors that play a role in the familial occurrence of coronary heart disease, very low density lipoprotein (VLDL) triglycerides, low density lipoprotein (LDL) cholesterol and high density lipoprotein (HDL) cholesterol were measured after preparative ultracentrifugation in first degree male relatives of coronary patients and in control subjects. The HDL cholesterol concentration was significantly lower in relatives of 20--71 years old than in controls. No increase of serum and LDL cholesterol was found. A low level of HDL cholesterol was observed even in the younger relatives who are less likely to have cardiovascualr disease. In older relatives low HDL cholesterol was found in the presence or absence of clinical evidence of coronary artery disease. The HDL-cholesterol concentration was inversely related to the VLDL triglycerides both in relatives and controls, but the regression lines were different ((P less than 0.001) for the relative (y = --0.166x + 0.43) and for the controls (y = 0.191x + 0.49). A low HDL cholesterol level appears to be a marker of relatives of coronary patients.

Decreased HDL cholesterol in prepubertal and pubertal children of CHD patients.

Prepubertal boys and pubertal girls and boys selected because of the occurrence of acute myocardial infarction in their father or mother were characterized by a low HDL cholesterol when compared to healthy controls. This observation extends our previous observations of low HDL cholesterol in adult relatives of CHD patients to the children of the same patients. The occurrence of an HDL abnormality in young children demonstrates that the low HDL cholesterol precedes the occurrence of cardiovascular disease. Low HDL cholesterol was associated with increased VLDL cholesterol in prepubertal children and pubertal boys without significant increase in VLDL triglycerides. Smoking and drinking habits, and physical activity which are environmental factors known to affect HDL did not differ between these children and the controls and cannot account for the observed differences. The results show that the low HDL cholesterol is detectable early in life in close relatives of CHD patients, persists throughout the lifespan and is possibly genetically determined.

HDL cholesterol levels in patients with myocardial infarction and their families.

The present study using a quartile distribution of myocardial infarction patients demonstrated that the first-degree relatives of the myocardial infarction patients with the lowest HDL cholesterol have similarly the lowest HDL cholesterol. Low HDL cholesterol among these relatives was not secondary to increased VLDL triglycerides, as it persisted when subjects with hyper VLDL triglycerides were excluded. Familial low HDL cholesterol could not be attributed to known environmental factors as their levels did not differ significantly between the groups compaired. There was a significant correlation between HDL cholesterol levels of the parents and that of their younger offspring. The correlation was not significant with the offspring aged 20 and over. It appeared that there was a familial trend in low HDL cholesterol levels, more apparent among the young offspring than among the adult offspring, who may possibly not share any more the parental environment for factors liable to influence HDL cholesterol. This finding is compatible with a hereditary trait.

Actin stress fiber content of regenerated endothelial cells correlates with intramural retention of intermediate plus low density lipoproteins in rat aorta after balloon injury.

The rat aortic model of endothelial injury (balloon catheter induced) has been used to establish whether changes in protein intramural penetration in specific areas of the injured aorta were accompanied by phenotypic modifications of the regenerated endothelial cells covering these particular regions. Iodinated lipoproteins (IDL/LDL fraction) and albumin were used as tracers to localize protein permeability and retention in the aorta. Lipoproteins, but not albumin, were retained in the thickened areas covered with regenerated endothelium (i.e., 60 days after balloon induced injury). Neither lipoproteins nor albumin were retained in the other aortic areas studied, including the intimal thickening of de-endothelialized areas (15 days after injury). The relative volume of cytoplasmic stress fibers was significantly increased in regenerated endothelium covering thickened areas as compared with the other regions of the injured or normal aorta. The accumulation of lipids usually observed in atherosclerotic lesions, compatible with the trapping of lipoproteins by the matrix component of the intimal thickening, may be related to modulated features of endothelial cells regenerated over thickened areas of the aorta.

Interference of dimethyl alpha-(dimethoxyphosphinyl) p-chlorobenzyl phosphate (SR-202) in thyroid hormone metabolism: evidence of inhibition of monodeiodination.

SR-202 is a non-iodinated potential lipid-altering agent. When administered (100 mg) three times per day for 3 days to six euthyroid subjects it was associated with a 30 +/- 3% (mean +/- S.E.M.) fall in 3,3',5-triiodothyronine (T3) (P less than 0.001), a reciprocal 104 +/- 14% rise in 3,3',5'-tri-iodothyronine (reverse T3, rT3) (P less than 0.01), and a 37 +/- 7% rise in thyroxine (T4) (P less than 0.001). Basal and TRH-stimulated TSH did not change. These results suggested that SR-202 was acting as an inhibitor of the peripheral monodeiodination of T4 to T3. During a second study the same subjects received the same dose of SR-202 for a further 3 days following 15 days of progressive substitutive treatment with L-T4, which they continued to take at 200 micrograms/day until the end of the study. Despite higher levels of thyroid hormones in the substituted subjects, similar results were observed, serum T3 falling by 40 +/- 2% (P less than 0.001), serum rT3 and T4 rising by 168 +/- 24% (P less than 0.01) and 37 +/- 9% (P less than 0.01) respectively. These changes provide compelling evidence that SR-202 is an inhibitor of the peripheral conversion of T4 to T3 that acts on thyroid hormone metabolism without provoking a counter-regulatory pituitary response. It might prove to be a useful tool for the clinical investigation of thyroid function.

The influence of metabolic control on very low density lipoprotein composition in hypertriglyceridemic type II diabetics. A study using heparin-sepharose chromatography.

The composition and heparin-binding capacity of very low density lipoproteins (VLDL) from type II diabetics prone to develop secondary hypertriglyceridemia have been examined. Twelve diabetic patients whose triglyceride levels normalized during short-term treatment for hyperglycemia were studied. Normalization of triglyceride values reduced plasma levels of VLDL without modifying its relative lipid composition. There was, however, an increase in its relative apoprotein (apo) content, to which apo B made a greater percentage contribution. The calculated average particle diameter of posttreatment VLDL was reduced. The fraction of VLDL binding to heparin increased after treatment. Binding was strongly correlated to the apo B content and, to a lesser extent, to the apo E content. The data suggest that treatment of hyperglycemia favorably modified VLDL such that they more closely resemble VLDL from normolipidemic subjects, with potentially beneficial physiological consequences.

[Serum lipoproteins in family members of myocardial infarct victims]. / Etude des lipoprotéines sériques dans les familles de malades victimes d'infarctus du myocarde.

Men 40 to 59 years old, first degree relatives of patients with myocardial infarction had a lower HDL-cholesterol concentration than a control group. This is in analogy with the low concentration of HDL-cholesterol observed in the myocardial infarction patients themselves. LDL and VLDL in relatives were not elevated in comparison to the controls. The low HDL-cholesterol could be the expression of a familial defect in cholesterol transport.

[Dietary lipids and serum lipids in adolescents, based on the Geneva study of the precursors of atherosclerosis]. / Lipides alimentaires et lipides sanguins chez les adolescents, d'après l'étude genevoise des précurseurs de l'athérosclérose.

The relationship between serum lipids and nutrition, physical activity and body mass index were studies with a multifactorial analysis of variance in a group of 160 adolescents of both sexes (Table I). These relationships are complex and difficult to demonstrate; they give rise, however, to certain considerations of presumptive characteristics possibly linked with adolescence.

[Dyslipidemia in diabetes mellitus: significance, diagnosis and treatment]. / Dyslipidämie bei Diabetes mellitus: Bedeutung, Diagnostik und Behandlung.

Dyslipidemias are frequent in diabetic subjects: they increase the risk for atherosclerosis, in addition to the risk of diabetes mellitus per se. The pathogenesis of dyslipidemias differs between type I and type II diabetes: untreated type I diabetic subjects demonstrate frequently increased triglyceride concentrations due to diminished removal of triglyceride-containing particles, as a result of diminished activity of lipoprotein lipase. In addition, more triglycerides are produced due to increased lipolysis and increased free fatty acid supply to the liver. Type II diabetic subjects demonstrate very low density lipoprotein (VLDL) over-production due to obesity, insulin resistance and caloric overconsumption. In addition, triglyceride removal may be diminished due to diminished lipoprotein lipase activity when diabetes mellitus is poorly controlled. In addition, high density lipoprotein (HDL) is frequently lowered. During decompensation low density lipoprotein (LDL) concentrations may also increase. LDL particle composition is frequently abnormal. A severe dyslipidemia in diabetes mellitus is frequently a combined effect of diabetes mellitus and a congenital lipoprotein abnormality. The evaluation and treatment of dyslipidemias in diabetic subjects should be performed similarly to non-diabetics according to the guidelines published recently by the Working Group 'Lipids' of the Swiss Foundation of Cardiology. Additional accents in diabetic subjects are necessary. It is recommended that serum cholesterol, triglycerides and HDL are determined in every patient when diabetes mellitus is diagnosed. If serum cholesterol is greater than 6.5 mmol/l and the cholesterol/HDL-ratio is greater 6.5, dietary treatment should be reinforced; if its effect is insufficient, drug therapy should be considered.(ABSTRACT TRUNCATED AT 250 WORDS)