Lipoprotein structure in male subjects during in vivo lipolysis: effect of an anti-lipolytic treatment with acipimox

Plasma free fatty acid (FFA) levels were raised in healthy volunteers by the administration of a fatty meal and epinephrine infusion (0.15 mg/kg per min), to test the hypothesis that enhanced lipolysis might lead to changes in lipoprotein distribution and to the formation of lipoprotein complexes, also impairing the interconversion of high density lipoproteins (HDL). The study was carried out in double-blind conditions in volunteers pre-treated with either placebo or with acipimox, a nicotinic acid analogue with a long-lasting activity. Lipolysis was effectively induced; the treatment with acipimox prevented the rise of free fatty acids (FFA), and it also blunted the triglyceride (TG) increase occurring during the test. Whereas the mean low density lipoprotein (LDL) particle size did not change, the HDL particle distribution showed a progressive shift to smaller particles, both after placebo and after acipimox, the changes in size being maximal 3-7 h after the meal. Evaluation of HDL interconversion in plasma samples incubated at 37 degrees C for 6 h showed the expected accumulation of HDL2a particles, with a parallel decrease of HDL3a; however, this conversion was not affected by the presence of elevated FFA levels and no difference was noted in subjects taking either placebo or acipimox. These clinical data fail to confirm the hypothesis that enhanced lipolysis may lead to dramatic changes in plasma lipoprotein distribution and/or in aggregation or fusion of lipoprotein particles, as reported from in vitro experiments. This study, however, successfully achieved a useful model of exaggerated lipolysis and confirmed the important activity of a low dose nicotinic acid analogue in inhibiting lipolysis.

Plasma triglycerides and lipoprotein(a): inverse relationship in a hyperlipidemic Italian population

The relationship between plasma lipoprotein(a) (Lp(a)) levels and other clinical/biochemical variables was investigated in 1200 consecutive hyperlipidemic patients. Plasma Lp(a) concentrations were measured by a sandwich-ELISA method, while the patients were either on diet or diet plus lipid-lowering drugs; 38% of them had a plasma Lp(a) level > 30 mg/dl. The median plasma Lp(a) concentration and the frequency of Lp(a) > 30 mg/dl were significantly lower in individuals with severe hypertriglyceridemia vs. hypercholesterolemics (HC) or mixed hyperlipidemics (M-HLP), but similar to normolipidemic healthy controls. Patients with isolated moderate hypertriglyceridemia had Lp(a) levels intermediate between HC and M-HLP subjects. The in vitro addition of triglyceride-rich lipoproteins to normotriglyceridemic plasma did not affect the Lp(a) measurement. Plasma Lp(a) concentrations in the whole hyperlipidemic population correlated negatively with triglycerides and positively with total cholesterol, HDL-cholesterol and age, being unrelated to either body mass index or lipid-lowering treatment. In HC patients, the presence of tendon xanthomas was associated with twofold higher Lp(a) levels. These findings argue for a regulatory role of triglycerides on plasma Lp(a) levels in hyperlipidemic patients.

Increased postprandial lipemia in Apo A-IMilano carriers

Plasma lipid/lipoprotein changes were monitored after a fat load (65 g fat per square meter body surface area) in six carriers of the apolipoprotein A-IMilano (A-IM) variant and six age- and sex-matched control subjects. The magnitude of postprandial lipemia, calculated as the area under the curve (AUC) described by plasma triglyceride (TG) level versus time, was threefold higher in the A-IM carriers; however, after correction for the different baseline TG levels, it was similar to control subjects. Moreover, the magnitude of postprandial lipemia was positively correlated with baseline TG in both A-IM carriers (r = 0.77) and control subjects (r = 0.80), indicating that fasting TGs are a major determinant of postprandial response in all subjects. Postprandial lipemia was also inversely correlated with high density lipoprotein (HDL) and HDL2 cholesterol in both groups (A-IM, r = -0.81 and -0.79; control subjects, r = -0.87 and -0.94). Different from those in control subjects, the plasma apo A-I levels in the A-IM carriers decreased progressively while apo B increased up to 4 hours but decreased thereafter. Postprandial rises of low density lipoprotein TG but not of HDL-TG AUC were significantly higher in the A-IM carriers, even after normalization for the different fasting concentrations. These data show that the low plasma HDL levels of A-IM carriers, which are secondary to a primary structural alteration of the major HDL apolipoprotein, are associated with elevated fasting and postprandial TG levels and an anomalous postprandial redistribution of TG among lipoprotein classes.

Mechanisms of high-density lipoprotein reduction after probucol treatment: changes in plasma cholesterol esterification/transfer and lipase activities

Probucol treatment results in a significant reduction of plasma high-density lipoprotein (HDL) levels. Since the remodeling of HDL within the plasma compartment is a crucial determinant of HDL levels, the activities of several factors participating in the process, ie, lecithin:cholesterol acyltransferase (LCAT), cholesteryl ester transfer protein (CETP), and lipoprotein and hepatic lipases (LPL, HL), were evaluated in 15 hypercholesterolemic patients treated with probucol (1 g/d) for 8 weeks. Drug treatment was associated with significant reductions of HDL cholesterol ([HDL-C] -32%), HDL2-C (-65%), HDL3-C (-22%), apolipoprotein (apo)A-I (-27%), and apo A-II (-11%) levels and with the accumulation of small HDL in plasma. CETP activity increased by 48%, with minor changes in LCAT (-7%), LPL (+4%), and HL (-7%) activities. By linear regression analysis, CETP activity correlated inversely with HDL-C, HDL2-C, and apo A-I levels (r = -.63, -.52, and -.73, respectively) and with HDL particle size. In multivariate analysis, CETP activity was the strongest predictor of HDL-C levels, apo A-I levels, and HDL particle size. The hypothetical mechanism of probucol is a stimulation of CETP activity, resulting in the formation of triglyceride (TG)-enriched HDL. These are acted on by HL, leading to the accumulation of small HDL in plasma.

Prolonged retention of doubly labeled phosphatidylcholine in human plasma and erythrocytes after oral administration

The plasma kinetics of a preparation of dilinoleoyl phosphatidylcholine (DLPC) specifically labeled with 3H in the choline moiety and with 14C in the 2-fatty acid (FA) were evaluated in six healthy volunteers after oral administration. Retention of both isotopes in plasma exceeded expectations, with a half-life in the elimination phase of 172.2 h for 3H and 69.7 h for 14C. Up to 60 d after administration, there were still significant levels of radioactivity present in plasma. The relative stability of the [14C]FA label was demonstrated by the retention for more than 12 h of an isotope ratio close to that of the compound administered. The 14C label of DLPC remained in position-2, as assessed by cleavage of plasma phospholipids with phospholipase A2. The [3H]choline label showed an early incorporation into high density lipoproteins and subsequently into low density lipoproteins (LDL); conversely, the 14C radioactivity was rapidly incorporated into triacylglycerols that were mainly associated with very low density lipoproteins. Radioactivity measurements revealed that both isotopes remained the longest time in LDL. In red blood cell (RBC) lipids, [3H]choline radioactivity accumulated over time, with a plateau after 48 h, whereas FA radioactivity accumulated more rapidly and was followed by a progressive decay. Analysis of the isotope ratio in these cells suggested an early incorporation of lyso products followed by rapid transfer of FA from plasma. The RBC maintained considerable radioactivity for a prolonged time, thus acting as a possible reservoir for the DLPC administered.(ABSTRACT TRUNCATED AT 250 WORDS)

Bezafibrate lowers plasma lipids, fibrinogen and platelet aggregability in hypertriglyceridaemia

The effects of bezafibrate 400 mg/day (slow release formulation) on plasma lipids/lipoproteins and on selected haemostatic parameters were evaluated in a double blind cross-over study in patients with Type IIb and IV hyperlipoproteinaemia. Placebo treatment did not influence any of those parameters, but the drug significantly reduced plasma triglycerides (-45%) and VLDL cholesterol, as well as causing a 12% fall in total cholesterol and a 20% increase in HDL cholesterol. Apo AI levels were significantly increased following bezafibrate and Apo B was reduced by about 20%. In addition to changes in the plasma lipid profile, bezafibrate reduced the sensitivity of platelets to the aggregatory effect of collagen, with no effect on TXB2 production. Fibrinogen levels after bezafibrate treatment were significantly lowered, the effect being more marked in patients with hyperfibrinogenaemia. Bezafibrate did not influence the plasma fibrinolytic profile. It is concluded that bezafibrate, besides its beneficial effects on the plasma lipoprotein profile, can exert beneficial changes on specific haemostatic parameters.

Olive oil, corn oil, and n-3 fatty acids differently affect lipids, lipoproteins, platelets, and superoxide formation in type II hypercholesterolemia

To evaluate which dietary fat may provide the best response in terms of plasma lipids and lipoproteins and also of platelet aggregability and superoxide formation by white blood cells, 12 type II patients were randomly allocated to three different diets, which provided polyunsaturated fatty acids (corn oil), monounsaturated fatty acids (olive oil), and a supplementation of ethyl esters of n-3 fatty acids to a prudent diet. Olive oil and, more significantly, n-3 ethyl esters lowered total cholesterol best (-2.2% and -5.8%, respectively); the latter diet, as expected, also significantly lowered triglyceridemia (-21.4%). The corn-oil diet exerted a small, statistically significant reduction of high-density-lipoprotein cholesterol (HDL) (-4.3%), and it also lowered plasma total apo B concentrations (-3.8%). n-3 ethyl esters significantly raised both total (+3.1%) and particularly HDL2 cholesterol (+24%). Platelet reactivity was insignificantly reduced by the three regimens, but all three significantly reduced thrombin-stimulated formation of thromboxane B2. Finally, only the n-3 fatty acid supplementation significantly reduced O2- generation by adherent monocytes. Dietary unsaturated fatty acids are generally effective on the plasma lipid and lipoproteins in type II patients, but significant differences may be found between the three tested regimens.

Activity profile of gemfibrozil on the major plasma lipoprotein parameters

Gemfibrozil (G) is a widely used and highly effective fibric acid derivative. It acts both on lipoprotein disorders characterized by hypertriglyceridemia, as well as in hyperchlolesterolemia. The results of two separate studies are summarized, in order to elucidate the differential activity profile of the drug on the major plasma lipoprotein parameters. In a group of hypertriglyceridemic patients (Study I) the major activity of G was on the VLDL cholesterol (C) and triglyceride levels (respectively -40.4 and -35.7%), associated with a marked increase of the HDL-C levels, in particular in the HDL3 subfraction. In addition, apolipoprotein B levels were significantly reduced (-12%) in all treated patients. In Study II, treatment with G in severe hypercholesterolemia was compared to that with pravastatin, a major hydroxymethylglutaryl coenzyme A reductase inhibitor. G, in these patients, markedly reduced both total (-21.6%) and LDL-cholesterol (-24.4%) levels. The increase of HDL-C was less marked than in type IV patients but G, similarly to pravastatin, induced a significant reduction of apolipoprotein B, together with an increase (+19.2%) of apolipoprotein AII levels. These findings indicate that the activity profile of G is wider than expected and that it may include a reduction of LDL levels in severely hypercholesterolemic patients. The mechanism of this latter change is difficult to establish, although it may also be related to an improved delipidation of LDL, resulting in a more efficient interaction with peripheral high affinity receptors.

Differential effect of unsaturated oils and butter on blood glucose and insulin response to carbohydrate in normal volunteers

Plasma glucose and insulin responses were monitored in normal volunteers after a standard carbohydrate meal with unsaturated oils (olive and corn oil, in identical volumes) or butter. Both unsaturated oils almost totally blunted the glycaemic response; butter, instead, only delayed the plasma glucose rise, without significantly changing the area under the curve. The insulin rise was essentially unaffected by the three experimental meals, only a slight delay in the peak being observed with no differences between unsaturated oils and butter. These findings support previous data indicating reduced glucose levels after prolonged administration of olive oil, and reduced glycaemic response, in the absence of clear-cut insulin changes, differentiates unsaturated oils from indigestible fibres; it may be linked to an altered polysaccharide handling at the intestinal level.

Omega-3 fatty acids selectively raise high-density lipoprotein 2 levels in healthy volunteers

The effects of omega-3 fatty acid supplementation on high-density lipoprotein (HDL) subfraction distribution and composition were evaluated in five healthy volunteers taking 2.8 g/d of eicosapentaenoic acid (EPA) and 1.7 g/d of docosahexaenoic acid (DHA) for 6 weeks. This supplementation resulted in marked changes of the plasma fatty acid composition. Plasma total cholesterol (TC), HDL-cholesterol (HDL-C), and triglyceride (TG) levels did not change. HDL2-C increased by 74%, with a concomitant 19% decrease of HDL3-C; the HDL2 to HDL3 mass ratio increased from 0.30 +/- 0.19 to 0.47 +/- 0.28. The increase of HDL2 was confirmed by nondenaturing polyacrylamide gradient gel electrophoretic separation of HDL subclasses, otherwise showing no change in HDL particle size. After omega-3 supplementation, both HDL2 and HDL3 became cholesteryl ester (CE)- and TG-enriched and free cholesterol (FC)- and phospholipid (PL)-depleted. The reported findings provide a useful adjunct to the antithrombotic potential of omega-3 fatty acids.

Efficacy of cholestyramine does not vary when taken before or during meals

Compliance to cholestyramine treatment, often unsatisfactory, may become further problematic because of the common indication that the resin should not be taken with meals. Since there is no convincing data on the validity of this therapeutic schedule, 10 type IIA hyperlipoproteinemic patients received cholestyramine either before or during the 3 major meals, according to a cross-over protocol. Plasma lipid levels were monitored after 4 and 6 weeks of each treatment schedule. The efficacy of the resin, in terms of total cholesterol (-16.5% together with food vs. -17.2% before food) and of low density lipoprotein cholesterol reduction (-22.8% with food vs. -23.1% before food) did not differ. The side effect profile was also not different between the two treatment protocols. These findings suggest that there are no significant interactions between food and the anion exchange resin and that the hypocholesterolemic effect does not depend upon a specific timing, supposedly close to the gallbladder contraction. They are particularly significant in view of the future availability of new resins in liquid form, suitable for intake during meals.

Predictability of low-density lipoprotein levels during apheretic treatment of hypercholesterolaemia

The efficiency and efficacy of low-density lipoprotein (LDL) apheresis performed with a dextran sulphate cellulose (DSC) regenerating unit were tested in five familial hypercholesterolaemic patients. LDL apheresis was repeated four times at both bi-weekly and weekly intervals, processing one plasma volume each time. The efficiency of the procedure (i.e., the extent of lipoprotein removal) was nearly identical with both schedules. Efficacy parameters, i.e., decreases of plasma total and LDL cholesterol (TC and LDL-C) and apo B, were highly correlated (r greater than 0.96) with preapheresis levels, allowing an accurate prediction of the absolute lipid removal in the single individual. Plasma triglycerides, high-density lipoprotein cholesterol, apo A-I and apo A-II recovered rather rapidly, reaching 91-96% of the pre-apheresis values in 48 hours; the recovery of TC, LDL-C and apo B was much slower, with a relatively rapid early phase (80% recovery after about 7 days) followed by a successive slower rise. This pattern was highly reproducible in the single patient, allowing the definition of a simple mathematical model for an accurate (error less than 20%) prediction of the individual process. Based on this model one can design the treatment schedule necessary to maintain lipid levels within the desired range in the single individual. The hypolipidaemic efficacy of DSC apheresis appears, otherwise, not to be dependent upon the procedure per se, but on other individual factors, e.g. the amount of removable lipoproteins and the rate of lipid recovery; both can be predicted with sufficient accuracy.

Comparison of the lipoprotein and hemostatic changes after a triphasic and a monophasic low dose oral contraceptive in premenopausal middle-aged women

Metabolic and hemostatic effects of 2 low dose oral contraceptives (OCs), a triphasic (ethinylestradiol + (-)-norgestrel) and a monophasic (ethinylestradiol + desogestrel) preparation, were compared in a cross-over trial in fertile women over 35 years of age. Both combinations moderately affected plasma lipids, with 17-24% increases of total triglyceridemia. Triglycerides accumulate in low density lipoproteins, thus suggesting the possible formation of an atherogenic lipoprotein particle. Only the monophasic preparation increased high density lipoprotein (HDL)-cholesterol levels significantly, with a rise in HDL3 mass and cholesterol. OC treatment led to slight changes in HDL2 and HDL3 structure, with a rise of the cholesteryl ester and triglyceride contents, indicative of a stimulated cholesterol esterification and reverse transport. Changes in the hemostatic indexes (fibrinogen, antithrombin III and protein C) were negligible. The new low dose OCs, even when prescribed to relatively older women, affect to a relatively small extent lipid/lipoprotein metabolism, with the exception of changes in the low density lipoprotein composition.

Influence of serum triglycerides on the HDL pattern in normal subjects and patients with coronary artery disease

The distribution and structure of high density lipoprotein (HDL) subfractions were examined by rate zonal ultracentrifugation in 200 consecutive subjects, 86 of whom showed a stable hypertriglyceridemia, 22 with coronary artery disease. Among the remaining 114 normotriglyceridemic subjects, 75 were healthy and 39 had coronary disease. The serum levels of the HDL2 subfraction were reduced by 22% in the 39 normotriglyceridemic coronary patients, and by 21% in the whole group of hypertriglyceridemic subjects. No difference in the HDL3 levels was found in any of the studied group. There was a clear negative correlation between HDL2 levels and triglyceridemia in the case of healthy people, not in coronary patients. By contrast, triglyceridemia was negatively correlated with the HDL3 flotation rate, both in healthy subjects and coronary patients at all triglyceride levels. Compositional data indicate that in hypertriglyceridemic subjects, HDL2 levels are reduced because of an enhanced transfer-exchanged process between the enlarged VLDL pool and HDL; in contrast, in coronary patients, a defective maturation of the HDL3 particle is the most likely underlying mechanism. Both in hypertriglyceridemic individuals, as well as in coronary patients, the HDL subfraction distribution is rather similar and drastically different from that of normotriglyceridemic healthy subjects. The mechanisms of the two conditions are probably different and, whereas a low concentration of HDL2 is definitely a major risk factor for normotriglyceridemic individuals, in the case of hypertriglyceridemics other factors may come into play in the final determination of the coronary risk.

Apolipoprotein AIMilano. Disulfide-linked dimers increase high density lipoprotein stability and hinder particle interconversion in carrier plasma

The in vitro metabolism of high density lipoproteins (HDL) in carriers of the apolipoprotein AIMilano (apoAIM) mutant was investigated during incubation of whole plasma and isolated lipoprotein fractions. A reduced cholesterol esterification (16.5 versus 25.0% for controls) and a decreased exchange of lipids between HDL and lower density lipoproteins was observed during incubation (6 h at 37 degrees C) of AIM plasma. Control HDL3 were converted to larger, faster-floating HDL particles, whereas only a fraction of AIM HDL3 followed the same pathway. Incubations were also carried out by mixing HDL3 from controls and AIM carriers with a lipoprotein-depleted plasma fraction in the presence of triglyceride-rich particles isolated from Intralipid. AIM HDL3 again showed a reduced capacity for lipid exchange; some HDL3 particles followed a "normal" conversion to faster-floating, larger HDL, whereas the small AIM HDL3 were not modified, indicating that AIM HDL3 are a mixture of metabolically functional and nonfunctional particles. Following transformation of the apoAIM homo- and heterodimers into their normal counterparts, i.e. monomeric apoAI and -AII, by reduction and carboxamidomethylation of AIM HDL3, the modified HDL3 behave like control HDL3 during incubation with lipoprotein-depleted plasma and triglyceride-rich particles. The presence of AIM dimers is most likely responsible for the increased HDL3 stability in the AIM carriers, indicating that apolipoprotein composition plays a major role in HDL particle interconversion.

Plasma lipoprotein changes after treatment with pravastatin and gemfibrozil in patients with familial hypercholesterolemia

The ability of pravastatin, a new hydroxymethylglutaryl coenzyme A (HMG-CoA) reductase inhibitor, to lower plasma lipid levels and modify lipoprotein patterns was compared with that of gemfibrozil in 18 patients with familial hypercholesterolemia who participated in a 16-week, double-blind, parallel trial. Pravastatin proved better than gemfibrozil in lowering total and low-density lipoprotein (LDL) cholesterolemia: -23.6% and -28.2% versus -18.1% and -21.4%, respectively. A significant positive correlation was found between the starting level of serum cholesterol (both total and LDL) and the gemfibrozil-induced reduction (r = 0.72 and 0.69), whereas the hypocholesterolemic effect of pravastatin was apparently independent from pretreatment levels (r = 0.32 and 0.10). Apolipoprotein B concentrations were lowered by 25.4% (pravastatin) and 22.0% (gemfibrozil). Pravastatin and gemfibrozil reduced triglyceride levels by 13.9% and 49.4%, respectively. Both drugs increased the level of high density lipoprotein (HDL) cholesterol, but this change was significant only with gemfibrozil (p less than 0.05). The HDL subfraction structure and distribution were not modified by pravastatin treatment. Gemfibrozil, in contrast, increased HDL3 cholesterol level by 9% because of an enrichment of HDL3 particles in both free cholesterol and cholesteryl esters and lowered the flotation rate of HDL3 (p less than 0.05). LDL particles became smaller after gemfibrozil treatment (diameter: 25.4 +/- 0.3 nm vs 26.1 +/- 0.4 nm, p less than 0.01) and were not modified by pravastatin. This comparison shows a more pronounced efficacy of the HMG CoA reductase inhibitor on total and LDL cholesterol levels, also indicating that pravastatin acts by a single major mechanism, reducing the number of circulating LDL particles. Gemfibrozil may exert additional activities, possibly consequent to the stimulation of very low density lipoprotein catabolism.

Mechanisms of HDL reduction after probucol. Changes in HDL subfractions and increased reverse cholesteryl ester transfer

Treatment with probucol, a widely used lipid-lowering agent, is associated with a significant reduction of high density lipoprotein (HDL) cholesterol levels, but with an apparently improved removal of cholesteryl esters from tissues (e.g., from tendon xanthomas). The effects of probucol (500 mg twice daily) on HDL subfraction distribution and cholesteryl ester transfer activity were tested in 12 patients with stable type II hyperlipidemia [low density lipoprotein (LDL) cholesterol greater than 180 mg/dl] after a placebo-controlled cross-over trial. Probucol significantly lowered total cholesterol (-13.8%), LDL cholesterol (-9.1%), and HDL cholesterol (-30%). By rate zonal ultracentrifugation, a marked reduction of HDL2 cholesterol (-68%) was shown, whereas changes in HDL3 were less significant (-21%). These findings were confirmed by polyacrylamide gradient gel electrophoresis, typically showing a reduction or disappearance of HDL2b particles and the prevalence of particles in the HDL3a range. Cholesteryl ester transfer from HDL to lower density lipoproteins was significantly increased (30%) in all patients. These findings suggest that, in addition to the well-documented in vitro changes (prevention of LDL peroxidation and macrophage uptake), probucol characteristically modifies HDL particle distribution in vivo, and is associated with a significant increase of cholesteryl ester transfer activity.

Lipid effects of celiprolol, a new cardioselective beta-blocker, versus propranolol

The metabolic effects of celiprolol, a new beta-adrenoceptor blocking agent with intrinsic sympathomimetic activity and alpha 2-blocking properties, were evaluated in a series of patients with hypertension, both with and without hyperlipidemia. Propranolol was tested as the reference drug in a randomized double-blind trial. Of the 35 patients of both sexes who completed the study, 17 were hyperlipidemic (low-density lipoprotein cholesterol greater than or equal to 170 mg/dl) and 18 were normolipidemic. Both drugs exerted a similar hypotensive effect after gradual dose adjustment; however, propranolol reduced heart rate to a higher extent (-20.5%) than celiprolol (-7.7%). Propranolol determined a significant rise of total and very low-density lipoprotein (VLDL) associated triglyceridemia, whereas high-density lipoprotein cholesterol (HDL cholesterol) levels and the total cholesterol/HDL cholesterol ratios were significantly depressed, particularly in hyperlipidemic patients. Celiprolol, in contrast, slightly decreased triglyceridemia (significantly in the hyperlipidemic group at week 12) and caused a 5% increase of the HDL cholesterol levels. The total cholesterol/HDL cholesterol ratio was reduced by celiprolol at week 16 in both hyperlipidemic and normolipidemic patients. The effects of the two beta-adrenoceptor blockers on HDL cholesterol and triglyceride levels differed significantly after 12 and 16 weeks of treatment, which confirm the divergent metabolic effects of the two agents.

Apheretic treatment of severe familial hypercholesterolemia: comparison of dextran sulfate cellulose and double membrane filtration methods for low density lipoprotein removal

The two more widely available techniques for the extracorporeal removal of low density lipoproteins (LDL), dextran sulfate cellulose column and double membrane filtration, were comparatively tested in severe familial hypercholesterolemic patients, both acutely and during a continued 3-month treatment. The selective dextran sulfate procedure removed close to 60% of LDL and 16% of high density lipoproteins (HDL) upon each apheresis, vs. 42% and 32%, respectively, in the case of the semi-selective double membrane filtration. Upon long term biweekly treatments, LDL-cholesterol (LDL-C) decreased, with the selective procedure, from a pre-treatment level of 406.0 +/- 40.7 mg/dl to a value fluctuating between 295.4 +/- 33.8 mg/dl and 116.9 +/- 22.0 mg/dl (highest vs. lowest levels) whereas, in the case of double membrane filtration, LDL-C levels ranged between 334.8 +/- 39.8 mg/dl and 192.3 +/- 49.9 mg/dl. HDL-cholesterol levels were somewhat raised, to a higher extent with dextran sulfate apheresis. The LDL/HDL-cholesterol "atherogenic ratio", decreased from a pre-treatment value of 10.27 +/- 3.04 to values ranging between 3.61 and 6.82 with dextran sulfate and between 6.70 and 7.68 with double membrane plasmapheresis.

Effects of gemfibrozil on plasma lipoprotein-apolipoprotein distribution and platelet reactivity in patients with hypertriglyceridemia

The effects of gemfibrozil on plasma lipoprotein distribution and composition and on platelet function were investigated in 11 patients with stable hypertriglyceridemia, six belonging to Fredrickson type IIb and five to type IV. Gemfibrozil (600 mg twice a day) significantly reduced total and very low density lipoprotein (VLDL)--associated triglyceridemia (respectively-32.4% and -40.4%, after 6 weeks of treatment). No significant variations were noted in the lipid components of low-density lipoproteins; by contrast, a marked increase (18%) was detected in high-density lipoprotein (HDL)--associated cholesterol. Comparison of the two patient groups (type IIb and type IV) showed that those with type IIb had both a more significant reduction of triglyceridemia and a more marked increase of HDL-cholesterol. Apolipoprotein B levels were reduced in both groups (-12%) with no change in apolipoprotein AI. The cholesterol content in the HDL subfractions, separated by rate zonal ultracentrifugation, was raised in HDL3 (18%) and in HDL2 (14%). Both particles also showed significant increases of the cholesterol/protein and the cholesterol/phospholipid ratios. A non-statistically significant decrease in collagen-induced aggregation and in the release of thromboxane B2 was noted after treatment. These findings suggest that, similar to what was recently reported in normal individuals and in laboratory animals, the probable mode of action of gemfibrozil is in reducing the secretion of atherogenic lipoproteins, particularly VLDL, while stimulating the production of small HDL particles.

Controlled evaluation of fat intake in the Mediterranean diet: comparative activities of olive oil and corn oil on plasma lipids and platelets in high-risk patients

Activities of low-fat diets with olive oil or corn oil on lipids and platelets were studied in 23 middle-aged patients with high atherosclerosis risk for 8 wk. The olive oil diet had a polyunsaturated-saturated ratio of 0.33 vs 1.28 for the corn oil diet. Plasma total cholesterol was reduced with corn oil, but high-density lipoprotein cholesterol levels were lower with corn oil and unchanged or raised by olive. Plasma apolipoprotein B levels were equally reduced by both diets; apolipoprotein AI and the apo AI:B ratio rose only with olive oil. Plasma-glucose levels were lowered significantly with olive oil. Changes in platelet function were characterized by a reduced sensitivity to arachidonic acid (particularly with corn oil) and to collagen (particularly with olive). An olive oil diet with a moderate fat intake (about 30% of total calories) leads to favorable plasma lipoprotein and platelet changes.

Apolipoprotein AIMilano. Accelerated binding and dissociation from lipids of a human apolipoprotein variant

The lipid binding properties of apolipoprotein (apo) AIMilano, a molecular variant of human apolipoprotein AI, characterized by the Arg173----Cys substitution, was investigated by the use of dimyristoylphosphatidylcholine liposomes. Both the variant AIMilano and normal AI are incorporated to the same extent in stable complexes isolated by gel filtration, showing similar dimensions and stoichiometries. A higher affinity of apo-AIMilano for dimyristoylphosphatidylcholine is suggested by the faster association rate of the variant apoprotein compared to normal AI; similarly, apo-AIMilano is more readily displaced by guanidine hydrochloride from the isolated dimyristoylphosphatidylcholine-apoprotein complexes. When the secondary structure of apo-AIMilano was investigated by spectrofluoroscopy and circular dichroism, a higher fluorescence peak wavelength and a lower alpha-helical content were detected in the variant apoprotein compared to normal AI. The substitution Arg173----Cys in the AIMilano dramatically alters the amphipathic nature of the modified alpha-helical fragment of apoprotein AI. The association rate with lipids is accelerated by an increased exposure of hydrophobic residues. The reduced stability of the lipid-apoprotein particles is possibly mediated by a reduction in the number of helical segments involved in lipid association. The high flexibility of the AIMilano apolipoprotein in the interaction with lipids may explain its accelerated catabolism and the possibly improved uptake capacities for tissue lipids.