Effects of treatment of hypertriglyceridaemia with gemfibrozil on serum lipoproteins and the transfer of cholesteryl ester from high density lipoproteins to low density lipoproteins

Chronic co-exposure to chlorpyrifos and deltamethrin pesticides induces alterations in serum lipids and oxidative stress in Wistar rats: mitigating role of alpha-lipoic acid

The study evaluated the effect of combination of chlorpyrifos (CPF) and deltamethrin (DLT) on serum lipid profiles and oxidative stress in rats, and the mitigating role of alpha-lipoic acid (ALA). Thirty male rats were used for the 120-day study. Serum samples obtained at termination were evaluated for the levels of triglyceride (TG), total cholesterol (TC), high-density lipoprotein (HDL), malondialdehyde (MDA), and the activities of antioxidant enzymes. The levels of low-density lipoprotein-cholesterol (LDL), very low-density lipoprotein-cholesterol (VLDL), and atherogenic index (AI) were calculated. The pesticide combination elevated the levels of TG, TC, LDL, VLDL, AI, and MDA, and decreased HDL level, and activities of CAT, SOD, and GPx. The alterations induced by CPF and DLT were alleviated by ALA, partly through its antioxidant properties. In conclusion, co-exposure to DLT and CPF altered serum lipids and increased oxidative stress changes in the rats, which were ameliorated by ALA.

Apolipoproteins AI and B as therapeutic targets

Currently the apolipoprotein B:AI ratio integrates information about the potential for cardiovascular disease (CVD) risk reduction better than any other lipid or lipoprotein index. Certainly it could, with benefit, replace serum cholesterol and HDL cholesterol in the estimation of CVD risk. Defining the therapeutic target of statin therapy in terms of serum apolipoprotein B (apo B) rather than LDL cholesterol could also help to optimize statin treatment. Deciding whether a therapeutic response is adequate also requires knowledge of whether there is persisting hypertriglyceridaemia, because this gives an indication of whether small dense LDL is likely to have been satisfactorily reduced. Raising low levels of HDL, probably best measured as apo AI, may also prove to be an important aim of treatment. This is, however, a more complex issue and also depends on the mechanism by which a particular therapy alters HDL levels and on whether the capacity of HDL to perform its anti-inflammatory and antioxidative functions is restored. A meta-analysis of randomized clinical trials of statins in which apo B and apo AI have been reported could provide valuable information.

The effect of atorvastatin on serum lipoproteins in acromegaly

OBJECTIVE

Acromegaly is associated with long-term adverse effects on cardiovascular mortality and morbidity. Reducing growth hormone secretion improves well-being and symptoms, but may not significantly improve the lipoprotein profile. An additional approach to cardiovascular risk reduction in acromegaly may therefore be to target lipoprotein metabolism directly. In this study we investigated the effect of statin treatment.

DESIGN

Double blind, placebo-controlled, crossover study of the effects on circulating lipoproteins of atorvastatin 10 mg daily vs. placebo. Each treatment was given for 3 months in random order.

SUBJECTS

Eleven patients with acromegaly.

MEASUREMENTS

Lipids, lipoproteins, apolipoproteins, enzyme activity and calculated cardiovascular risk.

RESULTS

Atorvastatin treatment compared to placebo resulted in a significant decrease in serum cholesterol (5.85 +/- 1.04 mmol/l vs. 4.22 +/- 0.69 mmol/l; mean +/- SD; P < 0.001), low-density lipoprotein (LDL) cholesterol (2.95 +/- 1.07 mmol/l vs. 1.82 +/- 0.92 mmol/l; P < 0.001), very low-density lipoprotein (VLDL) cholesterol (0.31 (0.21-0.47) mmol vs. 0.23 (0.13-0.30) mmol/l median (interquartile range); P < 0.05), apolipoprotein B (111 +/- 28 mg/dl vs. 80 +/- 18 mg/dl; P < 0.001), and calculated coronary heart disease risk (6.8 (3.3-17.9) vs. 2.8 (1.5-5.7)% over next 10 years; P < 0.01). Serum triglyceride was 1.34 (1.06-1.71) mmol/l on placebo and 1.14 (0.88-1.48) mmol/l on atorvastatin (ns). HDL cholesterol, apolipoprotein A1 and Lp(a) concentrations and cholesteryl ester transfer protein and lecithin: cholesterol acyl transferase activities were also not significantly altered.

CONCLUSION

Atorvastatin treatment was safe, well tolerated and effective in improving the atherogenic lipoprotein profile in acromegaly.

Pharmacological modulation of cholesteryl ester transfer protein, a new therapeutic target in atherogenic dyslipidemia

In mediating the transfer of cholesteryl esters (CE) from antiatherogenic high density lipoprotein (HDL) to proatherogenic apolipoprotein (apo)-B-containing lipoprotein particles (including very low density lipoprotein [VLDL], VLDL remnants, intermediate density lipoprotein [IDL], and low density lipoprotein [LDL]), the CE transfer protein (CETP) plays a critical role not only in the reverse cholesterol transport (RCT) pathway but also in the intravascular remodeling and recycling of HDL particles. Dyslipidemic states associated with premature atherosclerotic disease and high cardiovascular risk are characterized by a disequilibrium due to an excess of circulating concentrations of atherogenic lipoproteins relative to those of atheroprotective HDL, thereby favoring arterial cholesterol deposition and enhanced atherogenesis. In such states, CETP activity is elevated and contributes significantly to the cholesterol burden in atherogenic apoB-containing lipoproteins. In reducing the numbers of acceptor particles for HDL-derived CE, both statins (VLDL, VLDL remnants, IDL, and LDL) and fibrates (primarily VLDL and VLDL remnants) act to attenuate potentially proatherogenic CETP activity in dyslipidemic states; simultaneously, CE are preferentially retained in HDL and thereby contribute to elevation in HDL-cholesterol content. Mutations in the CETP gene associated with CETP deficiency are characterized by high HDL-cholesterol levels (>60 mg/dL) and reduced cardiovascular risk. Such findings are consistent with studies of pharmacologically mediated inhibition of CETP in the rabbit, which argue strongly in favor of CETP inhibition as a valid therapeutic approach to delay atherogenesis. Consequently, new organic inhibitors of CETP are under development and present a potent tool for elevation of HDL in dyslipidemias involving low HDL levels and premature coronary artery disease, such as the dyslipidemia of type II diabetes and the metabolic syndrome. The results of clinical trials to evaluate the impact of CETP inhibition on premature atherosclerosis are eagerly awaited.

High-density lipoprotein and coronary heart disease: lessons from recent intervention trials

Epidemiologic studies have consistently implicated low plasma high-density lipoprotein cholesterol as an important, independent risk factor for the development of coronary heart disease. However, clinical trials specifically designed to evaluate the role of lipid therapy in patients with low high-density lipoprotein cholesterol have only been recently reported. They include two trials with angiographic end points, the Lopid Coronary Angiography Trial and the Bezafibrate Coronary Atherosclerosis Intervention Trial, and three clinical end points trials, the Air Force/Texas Coronary Atherosclerosis Prevention study, the Department of Veterans Affairs High-Density Lipoprotein Intervention Trial, and the Bezafibrate Infarction Prevention study. These and other trials clearly indicate that persons with coronary heart disease and high low-density lipoprotein cholesterol (>130 mg/dL [3.36 mmol/L]), with or without low high-density lipoprotein cholesterol, benefit from statin therapy. The Air Force/Texas Coronary Atherosclerosis Prevention study showed that persons at high risk of coronary heart disease but without known disease, who have moderate levels of low-density lipoprotein cholesterol as well as low levels of high-density lipoprotein cholesterol, also appear to benefit from statin therapy although the cost effectiveness of this approach is unclear. The results from the Department of Veterans Affairs High Density Lipoprotein Intervention Trial provide convincing evidence that patients without high low-density lipoprotein cholesterol and with established coronary heart disease and low high-density lipoprotein cholesterol benefit from gemfibrozil. This drug may be particularly beneficial for patients who, in addition to low high-density lipoprotein cholesterol, present with other features of the metabolic syndrome, such as obesity, glucose intolerance, and high triglycerides. Whether other fibrates, niacin, or statins lower coronary heart disease risk in persons with low high-density lipoprotein cholesterol in the absence of high or moderately high low-density lipoprotein cholesterol is unknown. (c)2000 by CHF, Inc.

Effects of fibrates on serum metabolic parameters

Fibric acid derivatives are a class of hypolipidaemic drugs used in the treatment of patients with hypertriglyceridaemia, mixed hyperlipidaemia and diabetic dyslipidaemia. Fibrate therapy results in a significant decrease in serum triglycerides and an increase in high-density lipoprotein (HDL) cholesterol levels. The latest drugs of this class are also effective in lowering low-density (LDL) cholesterol levels and can change the distribution of LDL towards higher and larger particles. The effects of fibrates on lipid metabolism are mostly mediated through the activation of peroxisome proliferator-activated receptors (PPARalpha). A number of angiographic and clinical trials have confirmed that fibrates can slow the progression of atherosclerotic disease and decrease cardiovascular morbidity and mortality. Recently published data suggest that the ability of fibrates to prevent atherosclerosis is not related only to their hypolipidaemic effects but also to other 'pleiotropic effects', such as their anti-inflammatory, antioxidant and antithrombotic effects, as well as their ability to improve endothelial function. Interestingly, fibrates may favourably influence the thrombotic/fibrinolytic system. In fact, most of these drugs can significantly decrease plasma fibrinogen levels and inhibit tissue factor expression and activity in human monocytes and macrophages. Some studies have shown that fibrates can improve carbohydrate metabolism in patients with dyslipidaemia, including diabetic patients. Among fibrates only fenofibrate can significantly decrease serum uric acid levels by increasing renal urate excretion. Fibrates, with the possible exception of gemfibrozil, can significantly increase serum creatinine and homocysteine levels. Finally, a reduction in serum alkaline phosphatase and gamma glutamyltranspeptidase (gammaGT) activity is a well-documented effect of therapy with fibrates. The fibrates are generally well-tolerated drugs with few side-effects. The most important side-effect is myositis, which is observed in patients with impaired renal function or when statins are given concomitantly.

Gemfibrozil treatment potentiates oxidative resistance of high-density lipoprotein in hypertriglyceridemic patients

BACKGROUND

Studies suggest that both oxidized low and high density lipoprotein (LDL and HDL) play a role in the pathogenesis of atherosclerosis. Gemfibrozil is widely used and is reported to increase cholesterol of LDL and HDL in hypertriglyceridemic patients. The aim of this study was to investigate the effect of gemfibrozil treatment on the oxidative status of lipoprotein particles in Fredrickson phenotype IV hypertriglyceridemic patients.

METHODS

Twenty-two patients, aged 38-64 years, with fasting plasma triglyceride concentrations between 2.90 and 8.97 mmol L(-1), were recruited and were given gemfibrozil 300 mg three times daily for 12 weeks. Venous blood samples were collected before gemfibrozil treatment, after 4, 8, or 12 weeks of treatment, and 4 weeks after termination of treatment, and used to analyse the plasma lipid profile, isolate lipoproteins, and analyse the chemical composition and in vitro oxidation of lipoprotein particles.

RESULTS

Gemfibrozil treatment resulted in a decrease in plasma total triglyceride levels and the triglyceride content of all lipoproteins. Plasma total cholesterol levels were decreased as a result of a decrease in very low density lipoprotein (VLDL) cholesterol levels. A slight increase in LDL cholesterol levels was observed, whereas the thiobarbituric acid-reactive substances (TBARS) of LDL were decreased and the lag and peak time of LDL to oxidation were unchanged and maximal diene production was decreased. Plasma HDL cholesterol levels, the surface-to-core ratio of HDL particles, and the resistance of HDL to oxidation were increased.

CONCLUSION

The decreased TBARS and diene production of LDL, increased HDL cholesterol levels, and increased resistance of HDL to oxidation may, in part, explain why gemfibrozil treatment was found to be generally beneficial in terms of protection against coronary heart disease.

Paraoxonase and atherosclerosis

There is considerable evidence that the antioxidant activity of high density lipoprotein (HDL) is largely due to the paraoxonase-1 (PON1) located on it. Experiments with transgenic PON1 knockout mice indicate the potential for PON1 to protect against atherogenesis. This protective effect of HDL against low density lipoprotein (LDL) lipid peroxidation is maintained longer than is the protective effect of antioxidant vitamins and could thus be more important. There is evidence that the genetic polymorphisms of PON1 least able to protect LDL against lipid peroxidation are overrepresented in coronary heart disease, particularly in association with diabetes. However, these polymorphisms explain only part of the variation in serum PON1 activity; thus, a more critical test of the hypothesis is likely to be whether low serum PON1 activity is associated with coronary heart disease. Preliminary case-control evidence suggests that this is indeed the case and, thus, that the quest for dietary and pharmacological means of modifying serum PON1 activity may allow the oxidant model of atherosclerosis to be tested in clinical trials.

Cholesteryl ester transfer protein gene expression is not specifically regulated by CCAAT/enhancer-binding protein in HepG2-cells

Cholesteryl ester transfer protein (CETP) mediates the exchange of neutral lipids among plasma lipoproteins and is expressed predominantly in liver and intestine. In band shift assays employing nuclear extracts of HepG2 cells we identified C/EBPbeta as the predominant C/EBP isoform involved in binding to the C/EBP consensus sequence within the 5' upstream region of the CETP gene. This was demonstrated by supershift experiments using antibodies specific for C/EBPalpha, C/EBPbeta and C/EBPdelta and an oligonucleotide containing a single point mutation (CAAT-->CTAT) in this site. Expression of a CETP promoter-fragment/luciferase construct in transiently transfected HepG2 and CaCo-2 cells and enhancement of promoter activity by co-transfection with human C/EBPalpha in HepG2 cells could be influenced neither by the mutation in the consensus sequence nor by elimination of this site together with a second potential binding site for C/EBP. Furthermore, transfection of HepG2 with human C/EBPalpha did not influence the synthesis of CETP by these cells. Our results indicate that the expression of C/EBP in HepG2 cells is not able (1) to influence specifically the expression of a transfected CETP promoter dependent reporter through binding to C/EBP sites in the promoter region and (2) to significantly enhance expression of the endogenous CETP gene.

Gemfibrozil for the secondary prevention of coronary heart disease in men with low levels of high-density lipoprotein cholesterol. Veterans Affairs High-Density Lipoprotein Cholesterol Intervention Trial Study Group

BACKGROUND

Although it is generally accepted that lowering elevated serum levels of low-density lipoprotein (LDL) cholesterol in patients with coronary heart disease is beneficial, there are few data to guide decisions about therapy for patients whose primary lipid abnormality is a low level of high-density lipoprotein (HDL) cholesterol.

METHODS

We conducted a double-blind trial comparing gemfibrozil (1200 mg per day) with placebo in 2531 men with coronary heart disease, an HDL cholesterol level of 40 mg per deciliter (1.0 mmol per liter) or less, and an LDL cholesterol level of 140 mg per deciliter (3.6 mmol per liter) or less. The primary study outcome was nonfatal myocardial infarction or death from coronary causes.

RESULTS

The median follow-up was 5.1 years. At one year, the mean HDL cholesterol level was 6 percent higher, the mean triglyceride level was 31 percent lower, and the mean total cholesterol level was 4 percent lower in the gemfibrozil group than in the placebo group. LDL cholesterol levels did not differ significantly between the groups. A primary event occurred in 275 of the 1267 patients assigned to placebo (21.7 percent) and in 219 of the 1264 patients assigned to gemfibrozil (17.3 percent). The overall reduction in the risk of an event was 4.4 percentage points, and the reduction in relative risk was 22 percent (95 percent confidence interval, 7 to 35 percent; P=0.006). We observed a 24 percent reduction in the combined outcome of death from coronary heart disease, nonfatal myocardial infarction, and stroke (P< 0.001). There were no significant differences in the rates of coronary revascularization, hospitalization for unstable angina, death from any cause, and cancer.

CONCLUSIONS

Gemfibrozil therapy resulted in a significant reduction in the risk of major cardiovascular events in patients with coronary disease whose primary lipid abnormality was a low HDL cholesterol level. The findings suggest that the rate of coronary events is reduced by raising HDL cholesterol levels and lowering levels of triglycerides without lowering LDL cholesterol levels.

Diabetic dyslipidaemia

The risk of coronary heart disease and atherosclerosis is increased in both Type 2 and Type I diabetes mellitus. The dyslipidaemia of Type 2 diabetes consists of hypertriglyceridaemia and low levels of high-density lipoprotein (HDL) cholesterol. In Type I diabetes, hypertriglyceridaemia is also present, but when glycaemic control is good, HDL cholesterol levels may be normal or even increased. In both types of diabetes, nephropathy is associated with an exacerbation of hypertriglyceridaemia, a decline in HDL cholesterol level and an increase in serum cholesterol. In the absence of nephropathy, serum cholesterol levels are typically similar to those of the background non-diabetic population. The risk of coronary heart disease (CHD) associated with serum cholesterol is, however, considerably higher in diabetics than in non-diabetic people, and is much less in diabetic populations living in countries where the average cholesterol level is low, even when hypertension is present. Currently, the strongest evidence that lipid-lowering drug therapy will decrease the risk of CHD, particularly in secondary prevention, comes from trials of statins that lower cholesterol. There is growing experimental and observational evidence that hypertriglyceridaemia, because of its effects on cholesteryl ester transfer, leading to the formation of a small low-density lipoprotein susceptible to oxidation, compounds the risk of serum cholesterol in diabetes. Both fibrates and statins can decrease this cholesteryl ester transfer. Further studies of fibrates with clinical end-points should clarify their role in the prevention of CHD. In the meantime, statins should be part of routine diabetic clinical practice, fibrates having a more limited role when hypertriglyceridaemia is extreme.

Triglycerides are more important in atherosclerosis than epidemiology has suggested

Epidemiology call be a useful guide to risk prediction. If, for example, the value of serum cholesterol, high density lipoprotein (HDL) cholesterol and triglycerides as predictors of future CHD events is considered, then generally the triglyceride level measured on a single occasion will add little to the prognostic information contained in cholesterol and HDL cholesterol. The serum triglyceride concentration is, however, often more strongly correlated with future CHD incidence in univariate analysis than is serum cholesterol. However, in multiple logistic regression analysis, particularly when HDL cholesterol is included, the strength of the apparent independent relationship between triglycerides and CHD incidence is weakened often to the point of insignificance in individual trials, although it is still evident on meta-analysis of all the epidemiological trials in which both HDL cholesterol and triglyceride levels were measured. The erosion of the relationship between triglycerides and CHD incidence when HDL is included in multiple logistic regression analysis is to some extent is an artefact of the greater biological variation of triglyceride concentrations compared with HDL cholesterol. When allowance is made for this triglycerides can have more predictive power than HDL. Important clinical decisions are generally not based on single measurements, but on a series which reduces the effect of biological variation. However, even more importantly epidemiology cannot tell us that lowering cholesterol or raising HDL cholesterol levels will have more therapeutic benefit than decreasing triglyceride levels. That can only be established in clinical trials. An overview of trials involving drugs, which have as their principal action triglyceride-lowering, revealed them to decrease CHD incidence as much as statins. In the trials the drugs, which principally lowered triglycerides, also produced small decreases in serum cholesterol. The decrease in CHD incidence was, however, more than would be predicted from a similar reduction in cholesterol achieved with statins. Epidemiology can thus be a poor guide to clinical decisions. Furthermore the epidemiological relationship between cholesterol, triglycerides, HDL and CHD gives us only limited insight into the mechanisms by which these lipids and lipoproteins are involved in atherogenesis and their relative importance in this process. Thus evidence from clinical studies linking hypertriglyceridaemia with potentially important atherogenic factors such as intermediate density lipoproteins, small dense LDL and increased cholesteryl ester exchange may provide a greater understanding of atherogenesis and potential sites of therapeutic intervention than epidemiology. There is thus evidence for the therapeutic value of lowering triglycerides and an emerging view that triglyceride-rich lipoproteins are frequently crucial in atherogenesis.

Mechanism of action of fibrates on lipid and lipoprotein metabolism

Treatment with fibrates, a widely used class of lipid-modifying agents, results in a substantial decrease in plasma triglycerides and is usually associated with a moderate decrease in LDL cholesterol and an increase in HDL cholesterol concentrations. Recent investigations indicate that the effects of fibrates are mediated, at least in part, through alterations in transcription of genes encoding for proteins that control lipoprotein metabolism. Fibrates activate specific transcription factors belonging to the nuclear hormone receptor superfamily, termed peroxisome proliferator-activated receptors (PPARs). The PPAR-alpha form mediates fibrate action on HDL cholesterol levels via transcriptional induction of synthesis of the major HDL apolipoproteins, apoA-I and apoA-II. Fibrates lower hepatic apoC-III production and increase lipoprotein lipase--mediated lipolysis via PPAR. Fibrates stimulate cellular fatty acid uptake, conversion to acyl-CoA derivatives, and catabolism by the beta-oxidation pathways, which, combined with a reduction in fatty acid and triglyceride synthesis, results in a decrease in VLDL production. In summary, both enhanced catabolism of triglyceride-rich particles and reduced secretion of VLDL underlie the hypotriglyceridemic effect of fibrates, whereas their effect on HDL metabolism is associated with changes in HDL apolipoprotein expression.

Effects of two different fibric acid derivatives on lipoproteins, cholesteryl ester transfer, fibrinogen, plasminogen activator inhibitor and paraoxonase activity in type IIb hyperlipoproteinaemia

We have investigated the effects of two fibric acid derivatives, bezafibrate mono (400 mg daily) and gemfibrozil (600 mg b.d.), in 29 patients with type IIb hyperlipoproteinaemia. All patients received placebo and each drug for 8 weeks in randomised order in a double-blind, cross-over study designed to evaluate any different effects of the drugs on serum lipoproteins, cholesteryl ester transfer protein (CETP), cholesteryl ester transfer activity (CETA), plasma fibrinogen, plasminogen activator inhibitor-I (PAI-1) or paraoxonase. Serum cholesterol decreased (P < 0.05) with gemfibrozil, but the effect of bezafibrate on serum cholesterol did not achieve statistical significance (placebo 8.34 +/- 1.05 (mean +/- S.D.), gemfibrozil 7.70 +/- 1.23 and bezafibrate 7.8 +/- 1.37 mmol/l). Both drugs decreased the serum triglyceride concentration (both P < 0.001) (placebo 4.39 (3.13-5.75) (median (interquartile range)), bezafibrate 2.26 (1.89-3.89) and gemfibrozil 2.00 (1.30-3.30) mmol/l) and very low density lipoprotein (VLDL) cholesterol (both P < 0.001) (placebo 1.18 (0.74-2.30), bezafibrate 0.59 (0.34-0.85) and gemfibrozil 0.48 (0.34-0.68) mmol/l). Discontinuous gradient ultracentrifugation (DGU) revealed that Sf 60-400 (large VLDL) decreased by more than 50% and Sf 20-60 (small VLDL) by more than 30% with each of the drugs (both P < 0.001), neither of which affected the composition of these lipoproteins. Gemfibrozil decreased the concentration of Sf 12-20 lipoprotein (intermediate density lipoprotein; IDL) by 23% (P < 0.01), whereas the effect of bezafibrate on this lipoprotein did not achieve statistical significance. Neither drug altered the concentration of apolipoprotein B or of total Sf 0-12 lipoproteins (low density lipoprotein, (LDL)). Both, however, significantly increased the quantity of free cholesterol in Sf 0-12 lipoproteins (P < 0.05). Overall the concentration of triglycerides decreased significantly in all lipoproteins isolated by DGU (Sf 0-12, Sf 12-20, Sf 20-60, Sf 60-400) on gemfibrozil treatment, but only in Sf 20-60 and Sf 60-400 on bezafibrate (all P < 0.05). Both drugs also increased serum high density lipoprotein (HDL) cholesterol (placebo 1.15 +/- 0.29, bezafibrate 1.27 +/- 0.38 (P < 0.01) and gemfibrozil 1.26 +/- 0.49 (P < 0.05) mmol/l) and HDL3 cholesterol concentration (placebo 0.59 +/- 0.12, bezafibrate 0.72 +/- 0.23 (P < 0.001) and gemfibrozil 0.70 +/- 0.24 (P < 0.01) mmol/l). Serum apolipoprotein A1 (apo A1) was increased (P < 0.05) by bezafibrate compared to gemfibrozil (placebo 103 +/- 26, bezafibrate 111 +/- 28 and gemfibrozil 102 +/- 25 mg/dl) and CETA from HDL to VLDL and LDL was decreased (P < 0.05) by bezafibrate compared to placebo, but the apparent decrease with gemfibrozil did not achieve statistical significance (placebo 39.6 +/- 17.7, bezafibrate 32.3 +/- 14.7 and gemfibrozil 33.8 +/- 15.0 nmol/ml/h). Neither drug affected the circulating concentration of CETP. Plasma fibrinogen was increased (P < 0.05) by gemfibrozil (placebo 4.16 (3.38-4.71) and gemfibrozil 4.65 (4.05-5.77) g/l) and was significantly lower (P < 0.001) on bezafibrate (3.60 (3.18-4.54) g/l) than on gemfibrozil treatment. There was a significant (P < 0.05) increase in PAI-1 activity with bezafibrate and a similar trend with gemfibrozil (placebo 41.2 (25.6-64.5), bezafibrate 50.5 (35.1-73.9) and gemfibrozil 48.5 (31.5-5.4 U/l). Neither fibrate influenced plasma concentrations of PAI-1 nor were the activities of lecithin:cholesterol acyl transferase or paraoxonase affected. The major difference in the action of the two drugs on lipoprotein metabolism was the greater effect of gemfibrozil in decreasing the overall serum concentration of Sf 12-20 lipoproteins and the triglycerides in Sf 12-20 and 0-12 lipoproteins. Bezafibrate, however, increased serum apo A1 concentration and significantly decreased CETA. The two drugs also had different effects on the plasma fibrinogen levels, which increased with gemfibrozil and tended to decrea

Production of small high-density lipoprotein particles after stimulation of in vivo lipolysis in hypertriglyceridemic individuals: studies before and after triglyceride-lowering therapy

In hypertriglyceridemic states, triglyceride enrichment of high-density lipoprotein (HDL) may play an important role in decreasing the HDL cholesterol and apolipoprotein (apo) A-1 plasma concentration. We have shown previously that HDL particles are transformed into small HDLs when lipolysis is stimulated in vivo or in vitro, and this process is more marked if the HDL is triglyceride-rich. The present study was conducted to determine whether the susceptibility of HDL to transformation can be altered by triglyceride-lowering therapy in humans. Seventeen moderately hypertriglyceridemic individuals (nine with type II diabetes mellitus and eight moderately hypertriglyceridemic nondiabetic subjects) were studied before and after 3 months of triglyceride-lowering therapy with gemfibrozil. Since no significant differences in postprandial and postheparin HDL metabolism were detected between type II diabetic and nondiabetic subjects, results are reported for the two groups combined (N = 17). Fasting HDL was triglyceride-rich with a preponderance of HDL3, and became more enriched with triglycerides postprandially. Heparin administration resulted in a rapid decrease in plasma and HDL triglycerides and an increase in plasma and HDL free fatty acids (FFAs). Postheparin, there was a reduction in HDL size and an increase in the proportion of small (HDL3c) HDL particles (HDL3c constituted 7.1% +/- 1.8% of total HDL preheparin and 26.6% +/- 3.8% postheparin, P < .001). Triglyceride-lowering treatment resulted in a decrease in fasting triglycerides (-54%, P < .001) and HDL triglyceride content (-36%, P = .002), an increase in fasting HDL cholesterol (19%, P = .004), and proportionately fewer (13.2% +/- 2.1%, P < .001) HDL3c particles formed postheparin. Postheparin HDL size correlated inversely with the fasting triglyceride level (r = -.55, P < .001) and HDL triglyceride concentration (r = -.34, P = .02). These results show that the postprandial increase in triglyceride levels in hypertriglyceridemic subjects is associated with increased production of small HDL particles when lipolysis is stimulated, and that lipid-lowering therapy can contribute to favorably reduce this postprandial production of small HDL particles. Further studies are needed to clarify how these abnormalities ultimately lead to a decrease of plasma HDL cholesterol and apo A-1 in hypertriglyceridemic states.

Ethanol-induced redistribution of cholesteryl ester transfer protein (CETP) between lipoproteins

Since alcohol drinking reduces the concentration and activity of plasma cholesteryl ester transfer protein (CETP), we investigated the effects of alcohol on its synthesis and secretion by perfusing rabbit livers for 4 hours in the absence or presence of ethanol. The quantity of CETP mRNA in the perfused livers did not differ between the control and ethanol (25 mmol/L or 50 mmol/L) perfusions. CETP activity was determined by incubating [3H]cholesteryl ester-labeled human LDL and unlabeled human HDL with the perfusion medium after removing the endogenous VLDL (secreted by the perfused liver) by ultracentrifugation. CETP activity in the perfusion medium increased at a linear rate that was not affected by ethanol. When the VLDL was removed by precipitation with polyethylene glycol or a heparin-Sepharose column instead of ultracentrifugation, practically no CETP activity was detected in the ethanol perfusions, whereas these procedures did not affect CETP activity in the control perfusions. Inhibition of ethanol oxidation by 4-methylpyrazole resulted in CETP activity similar to that of the controls. We conclude that ethanol does not affect the synthesis or secretion of CETP, but its oxidation may alter the distribution of CETP in lipoproteins. CETP seems to be present in VLDL as well as in HDL, and since VLDL is more rapidly catabolized with HDL, this may explain the low plasma CETP concentration associated with alcohol consumption.

Effect of gemfibrozil on the regulation of HDL subfractions in hypertriglyceridaemic patients

OBJECTIVES

To study changes of HDL subfractions and their regulation during gemfibrozil treatment in hypertriglyceridaemia.

DESIGN

Twenty patients with hypertriglyceridaemia were randomized to receive either 1200 mg day-1 gemfibrozil or placebo for 3 months. After a 6-week, single-blind placebo period, the patients were randomized to receive either gemfibrozil or placebo for 3 months in a double-blind study.

SETTING

The patients were studied as outpatients in the Third Department of Medicine, Helsinki University Central Hospital, Helsinki, Finland.

MAIN OUTCOME MEASURES

Ultracentrifugally isolated HDL subclasses; concentrations of apoA-I, apoA-II, LpA-I and LpA-I:A-II particles; post-heparin plasma lipoprotein lipase (LPL), hepatic lipase (HL) and plasma cholesteryl ester transfer protein (CETP) activities; phospholipid transfer protein (PLTP) and lecithine cholesteryl acyltransferase (LCAT) activities were measured in plasma from six patients from both groups.

RESULTS

Gemfibrozil increased the concentration of HDL cholesterol (+11.1%) because of the rise of HDL3 cholesterol (34.5%, P < 0.01). The concentration of LpA-I particles was reduced during gemfibrozil treatment (-12.4%, P < 0.05), while that of apoA-II increased (+12.3%, P < 0.01). The LpA-I to LpA-I:A-II ratio decreased significantly in the gemfibrozil group (-18.9%, P < 0.01). Gemfibrozil increased LPL and HL activities by 18.2% (P < 0.05) and by 19.6%, respectively. Plasma CETP activity was also increased during gemfibrozil treatment (+15.8%, P < 0.05).

CONCLUSION

The gemfibrozil-induced elevation of HDL3 and apoA-II may reflect the combined action of LPL, HL and CETP on plasma HDL metabolism.

Treatment of primary mixed hyperlipidemia with etophylline clofibrate: effects on lipoprotein-modifying enzymes, postprandial lipoprotein metabolism, and lipoprotein distribution and composition

In 17 patients with primary mixed hyperlipidemia we studied levels and composition of lipoproteins in fasting plasma, lipoprotein-modifying enzymes, and postprandial lipoprotein metabolism after an oral fat-tolerance test supplemented with vitamin A before, and 12 weeks after treatment with etophylline clofibrate. With treatment, fasting plasma cholesterol, triglycerides, and the levels of very low density lipoproteins (VLDL), intermediate density lipoproteins (IDL), and low density lipoproteins (LDL) decreased significantly; high density lipoprotein (HDL) cholesterol increased significantly. Treatment caused also an increase in the protein content of IDL, a decrease in the triglyceride content of LDL, and an increase in the size of LDL as assessed by gradient gel electrophoresis. Concentrations of triglycerides, chylomicrons, and chylomicron remnants after an oral fat load supplemented with vitamin A decreased by 33%, 30% and 6%, respectively (P < 0.005; P < 0.01; and P < 0.05). The activity of lipoprotein lipase and hepatic lipase in postheparin plasma increased by 51% and 45%, respectively (P < 0.01; P < 0.05). We found a decrease in the mass concentration of cholesteryl ester transfer protein (P < 0.05). Stepwise multiple regression analysis showed that the triglyceride content of LDL is determined primarily by fasting triglycerides (r = + 0.53, P < 0.05;baseline) and cholesteryl ester transfer protein (r = + 0.49, P < 0.05; 12 weeks); in contrast, the triglyceride content of HDL3 is determined exclusively by accumulation of postprandial triglycerides (r = + 0.67; P < 0.05; baseline) and postprandial chylomicrons (r = +0.87; P < 0.005; 12 weeks). We conclude that hypolipidemic treatment with etophylline clofibrate favorably affects the cardiovascular risk factor profile in primary mixed hyperlipidemia.

Decreasing triglyceride by gemfibrozil therapy does not affect the glucoregulatory or antilipolytic effect of insulin in nondiabetic subjects with mild hypertriglyceridemia

We studied the effects of gemfibrozil on glucose and fatty acid metabolism in subjects with mild endogenous hypertriglyceridemia. Twenty subjects (serum triglycerides, 3.2 +/- 1.4 mmol/L; age, 52 +/- 7 years; body mass index, 27.8 +/- 1.8 kg/m2) were randomly allocated to receive either placebo or gemfibrozil 1,200 mg daily for 12 weeks in a double-blind study. Gemfibrozil decreased serum total and very-low-density lipoprotein (VLDL) triglycerides by 53% and 57%, respectively, and serum apolipoprotein (apo) B concentration by 21%. Gemfibrozil had no effect on the diurnal concentration of free fatty acids (FFA). Neither did gemfibrozil change diurnal blood glucose or serum insulin concentrations. The endogenous glucose production rate remained unchanged in both groups during the treatment period, and was similarly suppressed by hyperinsulinemia. The rate of insulin-induced whole-body glucose disposal increased similarly both before (basal 10.8 +/- 1.8, low-dose insulin 10.5 +/- 2.1, and high-dose insulin 20.9 +/- 11.9 mumol.kg-1.min-1) and after (11.1 +/- 1.7, 10.7 +/- 1.2, and 18.6 +/- 7.9, respectively) gemfibrozil treatment. Rates of oxidative and nonoxidative glucose metabolism remained unchanged during gemfibrozil treatment. Basal pretreatment and posttreatment FFA turnover rates were similar in both study groups, as were the rates of substrate oxidation. In summary, gemfibrozil proved to be an effective serum triglyceride-lowering agent in patients with mild hypertriglyceridemia, but had no effect on the insulin sensitivity of glucose metabolism or of antilipolysis. These data support the idea that triglycerides per se do not cause insulin resistance, and that the triglyceride-lowering effect of gemfibrozil is not mediated via antilipolytic action.

The effects of fibrates on lipoprotein and hemostatic coronary risk factors

The effects of fibrates on lipoprotein profiles and lipoprotein physiology, as well as on selected coagulation and fibrinolytic factors are reviewed. It is concluded that the action of fibrates on these systems is such as to render the fibrates beneficial in atherosclerosis prevention.

Gemfibrozil treatment of the high triglyceride-low high-density lipoprotein cholesterol trait in men with established atherosclerosis

OBJECTIVE

To study the short-term efficacy, tolerability and safety of the treatment with gemfibrozil 600 mg twice daily or placebo in male patients with established atherosclerosis, with a lipid profile matching the 'high triglyceride-low high-density lipoprotein (HDL) cholesterol trait'.

DESIGN

Double-blind randomized placebo controlled prospective trial.

SETTING

Amsterdam Lipid Research Clinic at the Academic Medical Centre of the University of Amsterdam and the Slotervaart Training Hospital affiliated to the University of Amsterdam, Amsterdam, the Netherlands.

SUBJECTS

Thirty-five male patients, age 30-70, with established atherosclerosis and the high triglyceride-low HDL cholesterol trait.

MAIN OUTCOME MEASURES

Plasma total cholesterol, triglycerides, lipoproteins, apolipoproteins A1 and B100, clinical and laboratory safety parameters.

RESULTS

Seventeen patients in the gemfibrozil group and 16 patients in the placebo group completed the study period. Compliance was considered adequate. Mean (+/- standard deviation) plasma HDL cholesterol levels increased 20.3% (+/- 12.22) from 0.82 to 0.99 mmol L-1 in the gemfibrozil group against 9.9% (+/- 18.31) from 0.79 to 0.87 mmol L-1 in the placebo group (P = 0.001). Mean plasma triglyceride level fell 49.5% (+/- 14.27) from 3.65 to 1.82 mmol L-1 in the gemfibrozil group against an increase of 13.6% (+/- 40.31) from 3.62 to 4.01 mmol L-1 in the placebo group (P < 0.001). Although plasma HDL cholesterol and triglyceride levels improved in all patients, normalization of these lipoproteins was only observed in approximately half of them. Plasma total and low-density lipoprotein (LDL) cholesterol levels, as well as plasma levels of apolipoprotein (apo) A1, B100 and lipoprotein [Lp(a)], did not show significant alterations compared to the placebo. All safety parameters were comparable between the two groups and remained within the reference limits. Gemfibrozil was well tolerated during treatment. Minor inconveniences were equally distributed between the two treatment groups.

CONCLUSIONS

Gemfibrozil is an effective and safe drug in patients with coronary heart disease (CHD) and the high triglyceride-low HDL cholesterol trait.

Evaluation of effects of unmodified niacin on fasting and postprandial plasma lipids in normolipidemic men with hypoalphalipoproteinemia

PURPOSE

The aim of this study was to define the effects of unmodified niacin on basal lipids and lipoproteins and on the plasma triglyceride response to a fatty meal--postprandial or alimentary lipemia--in individuals with low levels of high-density lipoprotein cholesterol (HDL-C) and normal fasting cholesterol and triglyceride concentrations (normolipidemic hypoalphalipoproteinemia, isolated low HDL-C).

PATIENTS AND METHODS

Twenty-eight normolipidemic men (total plasma cholesterol concentration [TC] < 230 mg/dL [< 6 mmol/L], plasma triglyceride [Tg] < 250 mg/dL [2.75 mmol/L]) with low plasma concentrations of HDL-C were randomly assigned to increasing doses of crystalline niacin (up to 3,000 mg/d) or no drug for 12 weeks, then crossed over to the alternate regimen. Outcome measures included changes in plasma lipoproteins and alimentary lipemia.

RESULTS

Fifteen participants completed the study. Mean baseline HDL-C +/- SD was 31.7 +/- 6.2 mg/dL (0.82 +/- 0.16 mmol/L). Mean baseline TC, plasma concentration of low-density lipoprotein cholesterol (LDL-C), and Tg were 192 +/- 29.4 mg/dL (4.97 +/- 0.76 mmol/L), 123 +/- 27 mg/dL (3.17 +/- 0.69 mmol/L), and 197 +/- 75 mg/dL (2.17 +/- 0.83 mmol/L), respectively. Unmodified niacin treatment resulted in significant (P < 0.001) reductions of 14% in TC (to 165 mg/dL, 4.26 mmol/L), 40% in Tg (to 119 mg/dL, 1.31 mmol/L), and 18% in LDL-C (to 101 mg/dL, 2.60 mmol/L) and significant increases of 30% in HDL-C (to 42 mg/dL, 1.07 mmol/L), 100% in HDL2 cholesterol (from 5 mg/dL to 9 mg/dL, 0.12 mmol/L to 0.24 mmol/L), and 21% in HDL3 cholesterol (from 27 mg/dL to 33 mg/dL, 0.70 mmol/L to 0.85 mmol/L). Unmodified niacin treatment reduced alimentary lipemia by 45% (P < 0.02).

CONCLUSIONS

Crystalline niacin effectively raises HDL-C, lowers LDL-C, and reduces alimentary lipemia in patients with isolated low HDL-C. However, many patients have difficulty tolerating the drug, and supervision may be required to sustain patient compliance and avoid toxicity.

Combined effects of lipid transfers and lipolysis on gradient gel patterns of human plasma LDL

The triglyceride content of the plasma very-low-density lipoprotein (VLDL) fraction is the most important factor affecting the size of low-density lipoprotein (LDL) in humans. Because cholesteryl ester transfer protein (CETP) can influence the size distribution of LDL particles in human plasma, the implication of lipid transfers in the formation of small-sized LDL patterns, which have been associated with elevated plasma triglyceride levels, was investigated. The size distribution of LDL particles in 15 plasma samples was determined by electrophoresis of the plasma LDL fraction on 20 to 160 g/L polyacrylamide gradient gels. The apparent diameter of the major LDL subfraction was shown to correlate negatively with triglyceride concentrations (r = -.706, P < .005) and positively with both high-density lipoprotein cholesterol levels (r = .637, P < .02) and the high-density lipoprotein/VLDL + LDL cholesterol ratio (r = .768, P < .001). In addition, LDL size correlated negatively with both the ability of plasma LDL to donate cholesteryl esters (r = -.79, P < .001) and its ability to acquire triglycerides (r = -.72, P < .005). Whereas these observations indicated that CETP-mediated alterations of the triglyceride/cholesteryl ester ratio of the LDL core would contribute to changes in LDL diameter, they suggested that the formation of small-sized gradient gel LDL patterns would require another biochemical event, such as lipolysis, in addition to neutral lipid transfers. To test this hypothesis, total plasma samples with or without added VLDL (added triglyceride concentration, 2.0 g/L) were preincubated for 24 hours at 37 degrees C. Preincubation mainly induced the replacement of cholesteryl esters by triglycerides in the LDL core, and changes in LDL composition were greater when total plasma was supplemented with VLDL. Subsequently, isolated LDL was incubated in the presence of bovine milk lipoprotein lipase as a source of triglyceride hydrolysis activity. Lipolysis tended to reduce the size of the major LDL subpopulation, and the mean change in LDL diameter was significantly greater when plasma was preincubated with VLDL supplementation than when it was not (-0.6 +/- 0.3 versus -0.2 +/- 0.2 nm, respectively; (P < .01). Moreover, sequential effects of lipid transfer and lipolysis activities induced dramatic changes in the general shape of gradient gel LDL patterns. The largest plasma LDL subpopulations tended to disappear, and the formation of new, small LDL particles could be observed. The combined effects of neutral lipid transfers and triglyceride hydrolysis could account for variations of gradient gel LDL profiles in human plasma.(ABSTRACT TRUNCATED AT 400 WORDS)

Comparison of lipid-lowering effects of low-dose fluvastatin and conventional-dose gemfibrozil in patients with primary hypercholesterolemia

A total of 123 patients with primary hypercholesterolemia were randomized on a 2:1 ratio to receive either fluvastatin at 20 mg once daily at night (n = 82) or gemfibrozil at 600 mg twice daily (n = 41) in a double-blind, double-dummy comparison of the effects on plasma lipid parameters and tolerability over 8 weeks. All patients had either low-density lipoprotein cholesterol (LDL-C) concentrations > or = 160 mg/dL (4.1 mmol/L) in association with definite coronary artery disease (CAD) or > or = 2 risk factors, or LDL-C > or = 190 mg/dL (4.9 mmol/L) with no CAD and < 2 risk factors. All had triglyceride (TG) levels < or = 350 mg/dL (4.0 mmol/L). After 8 weeks of treatment, fluvastatin produced significant reductions from baseline of 17.4% (p < 0.001) in LDL-C, 13.2% (p < 0.001) in total cholesterol (TC), 13.8% (p < 0.001) in very low-density lipoprotein cholesterol (VLDL-C), and 6.4% (NS) in TG. High-density lipoprotein cholesterol (HDL-C) was increased by 5.6% (p < 0.001), and the ratio of LDL-C:HDL-C (Friedewald) was decreased by 21.2% (p < 0.001). Gemfibrozil reduced LDL-C by 15.8%, TC by 13.4%, VLDL-C by 32.2%, LDL-C:HDL-C by 24.8%, and TG by 34.2%, and increased HDL-C by 13.9% (all changes were statistically significant, p < 0.001) compared with baseline. Gemfibrozil produced significantly greater changes in VLDL-C (p < 0.01), HDL-C (p < 0.001), and TG (p < 0.001), but not in LDL-C: HDL-C, compared with fluvastatin. Both drugs significantly reduced apolipoprotein (apo) B and lipoparticles (Lp) E:B, and increased apo A-I but had divergent effects on LpA-I (increased with fluvastatin and reduced with gemfibrozil; p < 0.05). At the end of the study, 43.8% of fluvastatin patients and 45% of gemfibrozil patients achieved a reduction of > 20% in LDL-C levels. Normalization of LDL-C levels was achieved (according to European Atherosclerosis Society guidelines) by 13.4% of fluvastatin- and 14.6% of gemfibrozil-treated patients. Both drugs were well tolerated; adverse events occurred in 36.6% of fluvastatin recipients compared with 58.5% of patients taking gemfibrozil. No clinically notable elevations of aspartate or alanine aminotransferases, alkaline phosphatase, or creatine phosphokinase occurred. No patient developed new or worsening lens opacities associated with a reduction in optically corrected visual acuity. The most commonly reported adverse events were headache and gastrointestinal upset. There were no serious drug-related adverse events.

Drug control of reverse cholesterol transport

Reverse cholesterol transport identifies a series of metabolic events resulting in the transport of excess cholesterol from peripheral tissues to the liver. High-density lipoproteins (HDL) are the vehicle of cholesterol in this reverse transport, a function believed to explain the inverse correlation between plasma HDL levels and atherosclerosis. An attempt to stimulate, by the use of drugs, this transport process may hold promise in the prevention and treatment of arterial disease. Among the agents affecting lipoprotein metabolism, only probucol exerts significant effects on reverse cholesterol transport, by stimulating the activity of the cholesteryl ester transfer protein and, consequently, altering HDL subfraction composition/distribution. Another approach to the stimulation of reverse cholesterol transport consists of raising plasma HDL levels; studies in animals, either by exogenous supplementation or by endogenous overexpression, have shown a consistent benefit in terms of atherosclerosis regression and/or non-progression. Thus, it is time to consider different future treatments of atherosclerosis, combining the classical lipid-lowering treatments with innovative methods to promote cholesterol removal from the arterial wall.

Effect of gemfibrozil on high density lipoprotein subspecies in non-insulin dependent diabetes mellitus. Relations to lipolytic enzymes and to the cholesteryl ester transfer protein activity

Twenty patients (18 men, 2 women) with non-insulin dependent diabetes mellitus (NIDDM) were randomized to receive either gemfibrozil 1200 mg daily or placebo for 3 months in a double-blind study. The effect of gemfibrozil on plasma HDL subfraction distribution was studied with sequential and density gradient ultracentrifugation and in gradient gel electrophoresis. The concentrations of apo A-I, apo A-II, Lp A-I and Lp A-I:A-II particles were measured. Postheparin plasma lipoprotein lipase (LPL) and hepatic lipase (HL) activities and plasma cholesteryl ester transfer protein (CETP) activities were also determined. Gemfibrozil increased the concentration of HDL cholesterol (P < 0.01), which was due to the rise of HDL3 cholesterol (+16%), while in the placebo group these values remained unchanged. Gemfibrozil increased the concentrations of apo A-I(+12.6%, NS), apo A-II (+28.2%, P < 0.01) and Lp A-I:A-II particles (+21.6%, P < 0.06) but there were no changes in the placebo group. Neither gemfibrozil nor placebo had any effect on the concentration of Lp A-I particles. As determined by density-gradient ultracentrifugation, gemfibrozil increased the concentration of cholesterol in the most dense HDL fractions (mean density 1.193 g/ml, +22%, P < 0.05 and mean density 1.158 g/ml, +19.3%, P < 0.05). In gradient gel electrophoresis, the gemfibrozil-induced elevations of the cholesterol and protein were most pronounced in the HDL3a (8.8-8.2 nm) region. Gemfibrozil increased LPL and HL activities by 14.7% (P < 0.05) and by 18.8% (P < 0.01), respectively, while in the placebo group LPL and HL activities remained unchanged. Plasma CETP activity was also increased during gemfibrozil treatment while in the placebo group it remained unchanged. We conclude that gemfibrozil causes multiple changes in plasma HDL metabolism. The gemfibrozil-induced elevation of HDL3 and dense HDL subpopulations may reflect the concerted action of LPL, HL and CETP on plasma HDL metabolism.

Effect of gemfibrozil and lovastatin on postprandial lipoprotein clearance in the hypoalphalipoproteinemia and hypertriglyceridemia syndrome

Eleven men with hypoalphalipoproteinemia (HPAL; fasting plasma high density lipoprotein (HDL) cholesterol level of < 0.9 mmol/l), mild hypertriglyceridemia (HTG; triglycerides (TG) level of 1.75-7.5 mmol/l) and a normal calculated LDL cholesterol level (< 3.7 mmol/l) participated in a randomized, double-blind, double-placebo, crossover trial to compare the effect of two drugs, lovastatin (40 mg once daily) and gemfibrozil (600 mg twice daily), on clearance of postprandial lipoproteins. A 2-week washout period separated drug treatment periods of 6 weeks each. Ten subjects completed each treatment period. After ingestion of a vitamin A fat load, plasma, chylomicron and non-chylomicron retinyl palmitate (RP) and TG responses (areas under curves) were reduced in all subjects on gemfibrozil therapy and in 7 on lovastatin therapy. There was close correlation between change in fasting TG (but not fasting HDL-cholesterol) and change in postprandial RP areas on gemfibrozil but not lovastatin therapy. Postheparin lipoprotein lipase (LPL) and hepatic lipase (HL) activities were increased by gemfibrozil therapy while only a mild elevation in LPL activity alone was seen on lovastatin therapy. These data indicate that improvement in HTG is the main feature associated with improvement in postprandial lipemia and this is likely due to LPL-mediated enhancement of lipolytic hydrolysis. Gemfibrozil is more effective than lovastatin in attenuating postprandial lipemia in the HPAL/HTG syndrome.

Simvastatin-induced decrease in the transfer of cholesterol esters from high density lipoproteins to very low and low density lipoproteins in normolipidemic subjects

Hyperlipidemic patients often have an accelerated esterified cholesterol transfer (ECT) from high density lipoproteins (HDL) to very low (VLDL) and low density lipoproteins (LDL). We investigated the effect of simvastatin on ECT in twelve normolipidemic subjects. After 6 weeks of simvastatin administration, ECT was decreased by 23%. To determine the mechanism of action of simvastatin, we measured ECT in different recombination experiments, using an isotopic assay in which the transfer of labelled EC from HDL to VLDL/LDL was determined. When HDL of the treated subjects were incubated with VLDL/LDL and CETP fractions isolated from control plasma, no effect of simvastatin was observed, indicating that the drug did not alter the HDL-dependent ECT. This might be expected since simvastatin induced only minor modifications of HDL structure. When HDL and VLDL/LDL of control plasma were incubated with CETP fractions of the treated subjects, a clear reduction of ECT occurred after simvastatin administration. The decrease of plasma transfer activity was correlated to that of CETP concentration and accounted for the simvastatin-induced lowering of ECT. The diminution of plasma CETP was correlated to that of the apo B-containing lipoproteins concentration. This finding confirms previous reports suggesting a relationship between LDL level and CETP activity. In conclusion, our work shows that simvastatin administration results in a decrease of ECT and that this effect occurs through a lowering of plasma CETP activity.