Net mass transfer of plasma cholesteryl esters and lipid transfer proteins in normolipidemic patients with peripheral vascular disease.

The role of plasma cholesteryl ester transfer and lipid transfer proteins in atherosclerosis is unclear. Recent data suggest both antiatherogenic and atherogenic properties for cholesteryl ester transfer protein (CETP). The overall effect of CETP on atherosclerosis may thus vary depending on individual lipid metabolism. To test whether lipid transfer parameters are of importance even in patients without major lipid risk factors for atherosclerosis, CETP mass and activity, net mass transfer of cholesteryl esters between endogenous lipoproteins (CET), and phospholipid transfer protein (PLTP) activity were determined in plasma from 18 normolipidemic male patients with peripheral vascular disease and 21 controls. Furthermore, lecithin: cholesterol acyltransferase (LCAT) activity was tested. The results show that CETP mass, CETP activity, and LCAT activity are not different between patients and controls. However, specific CETP activity (CETP activity/CETP mass) is lower in the patients (P < .02). On the contrary, higher CET is observed in patients' plasma (P < .001). Increased plasma PLTP activity (P = .052) is demonstrable in the patients. If the data of all subjects are combined, CET correlates positively with triglycerides ([TG], r = .45, P < .001) and with PLTP activity (r = .32, P < .05) but negatively with specific CETP activity (r = -.37 P < .05). CET and specific CETP activity remain significantly different in TG-matched patients and controls and are more strongly interrelated (r = -.71, P < .001), suggesting a higher and selective influence of lipid transfer inhibitor(s) on CET and CETP activity in the patients. CET allows the best discrimination between patients and controls in univariate and multivariate analysis. Eighty-eight percent of the subjects are correctly classified by CET as a single parameter. The results suggest that increased CET in the patients may reflect atherogenic alterations in TG metabolism and/or in lipid transfer protein activities despite normal fasting lipoprotein levels.

Generation of reactive oxygen species and activity of platelet-activating factor acetylhydrolase in human monocyte-derived macrophages.

Monocytes were prepared from healthy human volunteers and were allowed to differentiate into macrophages by adhesion to plastic surface and cultured over 7 days in presence of either 10% fetal calf serum (FCS), human control serum or serum from hyperlipaemic patients. Hyperlipaemic serum stimulated the differentiation (measured as an increase in cellular protein and DNA content) to a higher extent when compared to control serum and FCS. With all sera a marked increase of the cellular activity of the enzyme platelet-activating factor acetylhydrolase (PAF-AH) and a tremendous decrease in the capacity of cells to generate reactive oxygen species (ROS) was observed. After seven days of culture the increase in PAH-AH activity was about 19-fold with hyperlipaemic serum, 11-fold with control serum and 6-fold with FCS. During the same period of time ROS generation measured as zymosan-induced chemiluminescence decreased by about 98% and no significant differences between the three types of serum were found. The results indicate that the activity of PAF-AH and the capacity of ROS generation which are both assumed to play an important role in the oxidation of low-density lipoproteins (LDL) and thus in the development of atherosclerosis, change in opposite direction during the differentiation of blood monocytes into macrophages, and that hyperlipaemic serum stimulates PAF-AH activity but not ROS generation.

Ex vivo investigation of blood monocyte and platelet behaviour in pigs maintained on an atherogenic diet.

Domestic pigs aged 4 months were fed for 16 weeks an atherogenic diet rich in cholesterol and saturated fatty acid. The increase of plasma cholesterol and triacylglycerol levels was found to be accompanied by a significant increase in the number of blood monocytes and platelets when compared to control animals. Furthermore, the atherogenic diet produced a small but significant reduction in the blood monocyte phagocytic capacity and adhesion to plastic surface. No significant differences between both groups were found when spontaneous platelet aggregation in whole blood was studied. However, platelets from pigs fed the atherogenic diet had a smaller mean cell volume compared to controls. The results indicate than an atherogenic diet may affect blood monocytes and platelets in pigs.

Increase in plasma total and lipoprotein cholesterol during incubation of whole blood samples at 37 degrees C--influence of LCAT inhibitors.

Incubation of whole blood samples at 37 degrees C caused a time-dependent increase in plasma cholesterol concentrations. In samples from 40 fasting healthy males, plasma cholesterol rose by 13.6 +/- 3% during 24 h (P less than 0.001). Changes in cholesterol concentrations were found in both the HDL fraction and the VLDL/LDL fraction. The increase in lipoprotein cholesterol concentrations correlated positively with the initial levels of HDL cholesterol and apo A-I; and with the original levels of VLDL/LDL cholesterol, apo B and triglycerides. The increase in plasma total cholesterol was not related to the HDL cholesterol and apo A-I concentrations. It was more pronounced in samples with elevated plasma concentrations of total cholesterol, VLDL/LDL cholesterol, apo B and triglycerides. The elevation in plasma total cholesterol resulted from an increase in cholesteryl esters, whereas free cholesterol decreased. After LCAT inhibition no changes in total, free and esterified cholesterol were observed. Therefore, increase in plasma cholesterol seems to represent a LCAT-dependent cholesterol transport out of blood cells.

Functional behaviour of mononuclear blood cells from patients with hypercholesterolemia.

Mononuclear cells were prepared from venous blood obtained from 20 patients with a newly diagnosed hypercholesterolemia and without clinical signs of vascular disease, and from 19 age and sex matched controls. Adhesiveness to plastic surface, phagocytic activity measured as ingestion of zymosan particles, and spontaneous motility of mononuclear cells from patients were significantly higher by 57%, 19% and 50%, respectively, when compared to controls. In controls chemotaxis induced by the chemotactic peptide FMLP was slightly higher than spontaneous motility measured in absence of FMLP, whereas in patients FMLP significantly inhibited cell motility by about 47%. With the exception of FMLP-induced chemotaxis the results indicate that mononuclear cells are hyperreactive in hypercholesterolemia.

[Effect of hypercholesteremic sera on endothelial cell proliferation in vitro]. / Der Einfluss von hypercholesterolämischen Seren auf die Endothelzellproliferation in vitro.

Human hypercholesterolemic serum increases proliferation of human umbilical endothelial cells in vitro. This might be due to an increased content of low molecular weight growth factors, which are released by blood cells, mainly thrombocytes. Hypercholesterolemia could increase endothelial cell turnover and expression of dysfunctional cells which may support atherogenic processes.

Enhanced net mass transfer of HDL cholesteryl esters to Apo B-containing lipoproteins in patients with peripheral vascular disease.

In vitro net mass transfer of HDL cholesteryl ester to apolipoprotein (Apo) B-containing lipoproteins (HDL-CET) was found to be nearly twofold higher in plasma from 35 male patients with peripheral vascular disease compared to the values of 27 age- and sex-matched healthy controls (P less than 0.001). Differences in HDL-CET were predominantly observed between normolipidemic patients and controls, and were also demonstrable in pairs of patients and controls with similar HDL cholesterol, VLDL + LDL cholesterol, and triglyceride concentrations. Within the control group, higher HDL-CET was found in individuals with enhanced triglyceride or VLDL + LDL cholesterol levels. This dependence was not observed in the patient group. Consequently, enhanced HDL-CET in the patients seems to be independent of plasma lipid levels.

Enhanced degradation of platelet-activating factor in serum from diabetic patients.

The degradation of platelet-activating factor (PAF) and lipid concentrations were measured in sera from 20 patients with insulin-dependent diabetes mellitus and from 20 age- and sex-matched healthy volunteers. The PAF-degrading capacity as well as triglycerides and total and very low density and low-density lipoprotein cholesterol were found to be significantly increased in the patients group, whereas the difference observed in high-density lipoprotein cholesterol was statistically nonsignificant. There were also a series of close relationships between the degradation of PAF and some lipid variables in the control group. These results confirm the parallel changes of lipoproteins and PAF-degrading capacity described previously in serum from atherosclerotic patients and extend it to patients suffering from diabetes mellitus.

Blood platelet behaviour in patients with a type I diabetes mellitus.

Platelets appear to be involved in the development of vascular diseases in diabetic patients. In a number of studies, platelet adhesion and aggregation has been found to be enhanced in diabetic patients indicating a platelet hyperreactivity. However, contradictory results on hyperreactivity of diabetic platelets towards agonists published in the literature leading to the problem of reliability of agonist-induced aggregation as a parameter which is able to reflect an altered platelet reactivity. Therefore, we introduced the quantification of actin filaments of platelets as an early indicator of platelet hyperreactivity. In 20 patients with type I diabetes mellitus agonist-induced aggregation, spontaneous aggregation, malondialdehyde (MDA)-formation, plasma lipid status and the ability of plasma to degrade platelet activating factor (PAF) as well as the G- to F-actin equilibrium of platelets were assayed. Compared to an age- and sex-matched control group F-actin values, spontaneous aggregation and PAF-hydrolase were significantly increased in diabetic patients.

The degradation of platelet-activating factor in serum and its discriminative value in atherosclerotic patients.

Platelet-activating factor (PAF) is transformed in vivo rapidly into the biologically inactive lyso-PAF. This reaction as well as lipid parameters were quantified in serum from 40 survivors of myocardial infarction and 36 healthy controls matched for age and body weight. The PAF-degrading capacity was 23% (p less than 0.001) higher in patients compared with the control group. Using the degradation of PAF as an univariate discriminator more than 70% of subjects were classified correctly. This is comparable with the discriminatory value of the best lipid variables, apolipoprotein B and HDL-cholesterol. Statistically significant differences in the degradation of PAF were found also by comparing subgroups which were matched for plasma levels of total cholesterol, VLDL/LDL-cholesterol or apolipoprotein B. The ratio by 48% (p less than 0.0001) in the case group was identified as an additional good discriminator between both groups. In contrast, platelet aggregation tests which were performed in acetylsalicyclic acid treated platelet-rich plasma discriminated poorly between patients and controls.

Lipoprotein pattern in long-term diabetes of an at least 35 years' duration. Results of the Erfurt Study.

All diabetic patients suffering from the disease for at least 20 years and living in the closed area of the Erfurt district in 1970 have been followed prospectively since that time. In 47 of them still alive in 1985, i.e. after more than 35 years of diabetes, serum lipid and apolipoprotein concentrations were measured and compared to those of non-diabetic subjects without cardiovascular diseases (n = 47) pair-matched by sex, age, and body weight. In males (n = 27) significantly (p less than 0.01) higher levels of HDL cholesterol and apolipoprotein A-I as well as lower concentrations of triglycerides and a lower total cholesterol/HDL cholesterol risk ratio than in nondiabetic control subjects could be found. In long-term diabetic females (n = 20), apolipoprotein A-I levels were also increased (p less than 0.02). Trends in HDL cholesterol and triglycerides were similar to those found in males but did not reach statistical significance. Higher concentrations of total cholesterol (p less than 0.02), LDL cholesterol (P less than 0.05), and apolipoprotein B (p less than 0.02), however, did not fit in with a beneficial lipoprotein pattern. The frequency of pathological lipoprotein patterns was not higher than among the non-diabetic control subjects (32% and 40%, respectively). According to these findings an antiatherogenic lipoprotein pattern might be considered, at least in males, as one of the determinants causing the multifactorial event of long-term survival in diabetes.

Serum lipids and apolipoproteins in relation to glycaemic control and diabetic nephropathy in long-term survivors of diabetes: results of the Erfurt Study.

Follow-up data of all 208 long-term diabetics (duration of the disease at least 20 years) living in the closed area of the Erfurt district in 1970 had demonstrated the importance of lipoprotein pattern for longevity. Now the dependence of lipoprotein levels on both the diabetes-related conditions nephropathy and glycaemic control has been examined in 47 of them, still alive in 1985 that means 35 or more years after the onset of diabetes. Glycaemic control was assessed by measuring the glycosylated haemoglobin (n = 44). Diabetic nephropathy was assumed in case of persistent proteinuria. Poor glycaemic control (n = 16) was associated with increased levels of atherogenic lipoproteins as reflected by higher concentrations of total cholesterol, LDL cholesterol, apolipoprotein B, and triglycerides, as well as a changed HDL composition indicated by a decreased HDL cholesterol/apolipoprotein A--I ratio. Higher ratios of total cholesterol to HDL cholesterol and apolipoprotein B to apolipoprotein A--I point to an increased risk of developing atherosclerotic diseases in poorly controlled diabetics. 86% of the well controlled long-term diabetics had non-pathological values of LDL cholesterol, triglycerides, apolipoprotein B, HDL cholesterol, and apolipoprotein A--I but only 31% of the poorly controlled patients did so. Diabetic nephropathy in the absence of chronic renal failure (n = 10) was characterized by higher values of LDL cholesterol, triglycerides, total cholesterol/HDL cholesterol, and apolipoprotein B/apolipoprotein A--I. 80% of the subjects with a pathological lipoprotein pattern were proteinuric or in poor glycaemic control or both. Therefore, it is concluded that prevention of these two conditions might help to delay atherosclerosis via its beneficial influence on lipoprotein metabolism.

Plasma from atherosclerotic patients exerts an increased degradation of platelet-activating factor.

Platelet-activating factor (PAF) is a naturally occurring phospholipid that exerts diverse biological activities. In the present study the degradation of PAF as well as lipid concentrations were measured both in plasma from 28 patients suffering from peripheral vascular disease and 18 healthy volunteers of comparable age. Beside some changes of the lipoprotein pattern it was also found that the capacity to degrade PAF is significantly elevated in the patient group. In view of this finding the question arises whether there is any link between the degradation of PAF and the development of atherosclerosis.

The role of lipoproteins in the degradation of platelet-activating factor.

Measuring both platelet-stimulating activity and liberation of acetate, the capacity of serum and individual lipoproteins to degrade the platelet-activating factor (PAF) was studied. The highest degrading effect relative to the protein content was found in very low density lipoproteins (VLDL) and in low density lipoproteins (LDL). The effect is about 10- and 100-fold higher than that of high density lipoproteins (HDL) and serum, respectively. In lipoprotein deficient serum (LPDS) less than 5% of serum activity is detectable. Considerable individual variations are observed measuring the degradation of PAF under standard conditions in plasma from 37 healthy volunteers. Moreover, this activity is shown to correlate strongly with the plasma concentration of LDL. On the other hand, a significant negative correlation was found between the PAF-degrading capacity and the plasma concentration of HDL. In contrast, the PAF-degradation is unrelated to the concentration of plasma triglycerides. The results point to a possible role of plasma lipoproteins in regulating the degradation of PAF released into the circulation.

Stimulation of lecithin:cholesterol acyl transfer by intravenous injection of heparin.

Intravenous injection of 100 IU heparin per kg body weight caused elevation of the lecithin:cholesterol acyl transfer rate in each one of 11 men, in whom before as well as 5 min and 30 min after heparin application the concentration of unesterified fatty acids in plasma did not reach 0.8 mmol/l. The plasma concentration of unesterified cholesterol in high-density lipoproteins (HDL) increased in parallel at the expense of unesterified cholesterol in very low-density lipoproteins (VLDL) and low-density lipoproteins (LDL). For HDL cholesteryl esters an opposite effect was observed. The results support the hypothesis of a participation of the lecithin:cholesterol acyl transferase (LCAT) in VLDL breakdown.

[Effectiveness of different intervention measures in children and adolescents with hypertension and lipid metabolism disorders]. / Effektivität unterschiedlicher Interventionsmassnahmen bei Kindern und Jugendlichen mit Hypertonie und Fettstoffwechselstörungen.

141 children and adolescents (7-21 years, mean age 14.2 years) showed values of blood pressure, total cholesterol and triglycerides greater than or equal to 90 percentile and HDL-cholesterol values less than or equal to 10 during an examination of 639 children of parents with distinct coronary risk factors or early percentile infarction. By randomization they were subdivided into two groups. (A and B) and underwent intervention measures of different intensity. While group B got only a unique recommendation concerning the preventive measures, in group A a regular, non medicamentous individual treatment was performed. After one year a decrease of blood pressure could be proved in the two groups. A significant decrease of total and HDL cholesterol was found only in group A. While the blood pressure was most clearly reduced in 7-13-year-old children, the most distinct lipid changes were shown in 14-17-year-old adolescents. An influence on body-weight and triglycerides could not be established. Our results confirm the possibilities and also the limits of preventive measures in childhood and adolescence. Apart from the intended decrease of blood pressure and total cholesterol the simultaneous decrease of HDL-cholesterol refers to open questions in the conception of the primary prevention, particularly in children.

Use of the microanalytical system KAPA for serial determinations of triglycerides, total cholesterol and HDL cholesterol in capillary plasma.

Enzymatic methods adapted to the KAPA system can be carried out in a final test volume of less than 10 mu 1. The procedure is mechanized, including the pre-analytical steps. Day-to-day precision is 2-6% C.V. for single determinations. Advantages of the technique are: (1) capillary plasma can be used; (2) reagent waste is reduced by about two orders of magnitude compared to common procedures, and (3) 400 specimens can be assayed by one technician per day. These conditions facilitate serial determinations, large scale screening, or repetitive monitoring of values in a group of individuals.

Intraindividual variability of plasma cholesterol and triglycerides and the effect of propranolol treatment.

In 114 male subjects cholesterol and triglyceride concentrations in plasma after overnight fasting were followed up during 12 weeks. About one third of the individuals showed pronounced day to day variations of their cholesterol or/and triglyceride levels. Considerable intraindividual variability was moreover found for HDL cholesterol. Plasma lipid instability was more frequent in hyperlipemics and in subjects with low HDL cholesterol than in normolipemics. It was tried to level out the fluctuations by a beta blocking agent. Propranolol was used and proved to reduce the fluctuations of total cholesterol. However, at the same time the concentrations of triglycerides were increased and those of HDL cholesterol decreased. Practical consequences of both the fluctuating plasma lipid concentrations and the propranolol effects are stressed.

The effect of propranolol treatment on total cholesterol, HDL cholesterol, triglycerides. Postheparin lipolytic activity and lecithin:cholesterol acyltransferase in hypertensive individuals.

Administration of 120 mg propranolol per day to hypertensive patients is followed by decreased plasma concentrations of total cholesterol and HDL cholesterol and increased concentrations of triglycerides. Postheparin lipolytic activity was reduced when measured 5 min after heparin administration. The activity of lecithin:cholesterol acyltransferase is diminished. Reduced activity of this enzyme by propranolol could be demonstrated in vitro as well.