High density lipoprotein alterations induced by bezafibrate in healthy male volunteers

Effect of bezafibrate treatment on the altered lipoprotein profiles in hypertriglyceridemic subjects

The effects of bezafibrate treatment on lipoprotein metabolism were investigated in hypertriglyceridemic subjects. Bezafibrate, a fibric acid derivative, was administered at 200-400 mg/day to 8 patients with hyperlipoproteinemia (type IIb and IV) for 3-6 months. We evaluated the effects of bezafibrate on the plasma levels of total cholesterol(chol), triglyceride(TG), and apoB. In addition, the lipid and apoB contents were also analyzed in VLDL, IDL, LDL and HDL fractions before and after the treatment. It was revealed that plasma levels of chol, TG and apoB significantly decreased after the treatment, 236.3 vs 210.9,192.4 vs 90.2 (p< 0.01) and 129.8 vs 116.2 (p<0.05) mg/dl respectively. VLDL-chol, VLDL-TG and VLDL-apoB dropped from 26.5,127.6 and 11.1 mg/dl to 9.1, 49.5 and 6.7 mg/dl respectively after the treatment. Regarding qualitative alterations of VLDL, TG/apoB, chol/apoB and TG + chol/apoB ratios in VLDL were significantly reduced, indicating that the size of VLDL was diminished by the treatment. In addition, HDL-chol increased from 40.4 to 60.8 mg/dl after the treatment. Consequently LDL-chol/HDL-chol significantly decreased. In conclusion, bezafibrate administration decreased the TG, chol and apoB content in VLDL, suggesting a reduced number of VLDL. Significant rise of HDL-chol and decrease of LDL-chol/HDL-chol are additional beneficial effects following bezafibrate treatment.

Postprandial reverse cholesterol transport in type 2 diabetic patients: effect of a lipid lowering treatment

Deterioration of reverse cholesterol transport (RCT), an important anti-atherogenic process, may contribute to the largely unexplained severity of cardiovascular risk in type 2 diabetic patients. Among other relevant metabolic perturbations is the impairment in type 2 patients of the postprandial increase in RCT which, in normal subjects, is associated with the transfer to HDL of PL from lipolyzed chylomicrons. We have explored the possibility that improvement of postprandial lipolysis by bezafibrate might also restore the stimulated level of postprandial RCT. Twelve male patients (HbA1c 7.6 +/- 1.6% triglycerides (TG) 4.5 +/- 2.4 mmol/l) were treated for 4 weeks with 400 mg bezafibrate and compared with seven age-matched controls. Lipoproteins were analyzed over 8 h after a 1000 Kcal fat load (80% lipid), serum mediated cholesterol efflux was evaluated using 3H-cholesterol labelled Fu5AH cells. Fasting efflux was lower in patients (17.9 +/- 3.3 vs 19.9 +/- 3.0 a. units, P < 0.05) and decreased postprandially in most instead of increasing, so that area under the time-curve (AUC) was 23% lower than in controls (140 +/- 23 vs 170 +/- 25 units x h, P < 0.001) The patients' HDL failed to acquire PL and gained TG in proportion to lipemia (r = 0.660, P < 0.001). Bezafibrate restored fasting efflux (19.6 +/- 3.6 units, P < 0.005 vs pretreatment) but not postprandial increase of efflux or HDL-PL. AUC of efflux was however improved to 155 +/- 23 units h (P < 0.02). Postprandial efflux related mainly to HDL-PL in controls and patients before treatment. HDL-TG emerged as a significant negative correlate common to all groups (r = -0.674, P < 0.001 8 h after the meal). Impairment of reverse cholesterol transport in diabetic patients might therefore be due to combined postprandial deficit of PL transfer and excess accumulation of TG in HDL. The significant improvement due to fibrate treatment might thus be related to the reduction of HDL-TG contents associated with the improvement of postprandial hyperlipemia.

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.

Effects of bezafibrate therapy on subfractions of plasma low-density lipoprotein and high-density lipoprotein, and on activities of lecithin:cholesterol acyltransferase and cholesteryl ester transfer protein in patients with hyperlipoproteinemia

We investigated the effects of 12 weeks of bezafibrate treatment on plasma lipoprotein subfraction levels and on activities of LCAT and CETP in 25 patients with hyperlipoproteinemia. Bezafibrate reduced plasma levels of VLDL-TC and VLDL-TG by 69% and 66% (P < 0.001) and plasma levels of IDL-TC and IDL-TG were decreased by 37% and 31% (P < 0.01). Bezafibrate had no significant effects on plasma levels of LDL1 (1.019 < d < 1.045)-TC and LDL1-TG in the study population as a whole but significantly increased the plasma level of LDL1-TC in the subgroup of 9 patients with type IV hyperlipoproteinemia. Bezafibrate reduced plasma levels of LDL2 (1.045 < d < 1.063)-TC, LDL2-TG by 48% and 44% (P < 0.001) in both type II and type IV hyperlipoproteinemic patients. Gradient polyacrylamide gel electrophoresis revealed a decrease in small LDL particles. Bezafibrate did not affect the plasma level of HDL2-TC but reduced the HDL2-TG concentration significantly (P < 0.001). Bezafibrate increased the plasma level of HDL3-TC by 37% and reduced the HDL3-TG level significantly by 20% (P < 0.001). Gradient polyacrylamide gel electrophoresis revealed an increase in HDL3a and a decrease in HDL2a. Bezafibrate suppressed the activities of LCAT and CETP by 21% (P < 0.001) and 17% (P < 0.01), respectively. The bezafibrate-induced decrease in plasma levels of small, heavy LDL might be related to its inhibition of LCAT and CETP activities which resulted in suppression of heteroexchange of HDL-EC with triglyceride in large, light LDL. The bezafibrate-induced increase in large HDL3 (HDL3a) could not be explained solely by its suppression of LCAT and CETP activities. The decrease of plasma small, heavy LDL as well as TG-rich lipoproteins by bezafibrate seems to be beneficial for prevention of atherosclerotic diseases.

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.

Decreased ability of high density lipoproteins to transfer cholesterol esters in non-insulin-dependent diabetes mellitus

Esterified cholesterol transfer (ECT) from high density lipoproteins (HDL) to very low (VLDL) and low density lipoproteins (LDL) may be abnormal in situations at high risk for atherosclerosis. It has been shown to increase in insulin-dependent diabetes and to decrease in non-insulin-dependent diabetes (NIDD). Since the net transfer of esterified cholesterol (EC) results from a bidirectional exchange between HDL and VLDL/LDL, we developed a transfer assay specifically designed to measure the unidirectional transfer of EC from HDL to lipid emulsions according to first-order kinetics. Our results show that in NIDD the rate constant of HDL-dependent ECT is decreased by 30% by comparison with control subjects. Analysis of HDL composition revealed that, in both groups, HDL-dependent ECT was positively correlated with the free cholesterol/phospholipid ratio (r = 0.94; P < 0.001) and negatively correlated with the triglyceride/EC ratio (r = -0.85; P < 0.001). It is concluded that, besides the known defect of acceptor lipoproteins, the abnormality of ECT in NIDD is also caused by a decreased ability of HDL to act as an EC donor, presumably because of a change in composition. In addition, our work shows that the amount of EC lost by HDL during the reaction transfer is counterbalanced by a reciprocal equimolar transfer of triglycerides.

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.

Mode of action of fibrates

Fibrates are a class of hypolipidaemic drugs that effectively reduce plasma triglyceride and cholesterol levels, but also raise HDL cholesterol. In recent years the attention of pharmacologists and clinicians to fibrates has been renewed also in the light of a multifaceted action on plasma lipids as well as on factors modulating the thrombotic homeostasis in blood. The mechanisms of actions underlying these effects are discussed in this short review.

Reverse cholesterol transport: physiology and pharmacology

Reverse cholesterol transport identifies a series of metabolic events resulting in the transport of cholesterol from peripheral tissues to the liver and plays a major role in maintaining cholesterol homeostasis in the body. 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 seems to be of great promise in the prevention and treatment of arterial disease. Only few drugs are now known that can modify the activity of the various factors involved in the process. Clofibrate reduces cholesterol esterification, but the newer fibric acids are generally ineffective as anion-exchange resins. Probucol directly increases the activity and mass of cholesteryl ester transfer protein, thus possibly improving the physiological process of cholesterol removal from tissues. The few available data on the effects of drugs on reverse cholesterol transport should stimulate the search for new agents specifically stimulating this antiatherogenic process.

Serum lipoproteins, apolipoproteins and very low density lipoprotein subfractions during 6-month fibrate treatment in primary hypertriglyceridaemia

Serum lipoproteins and apolipoproteins were studied in 14 hypertriglyceridaemic (HTG) patients during a 24-week period of treatment with gemfibrozil, and after a 6-week washout period. A marked decrease in very low density lipoprotein (VLDL) cholesterol and triglyceride was observed. There was an increase in high density lipoprotein (HDL) cholesterol, particularly the HDL3 component. A slight increase in low density lipoprotein (LDL) cholesterol was observed after 12 weeks, but this had almost disappeared after 24 weeks. The treatment resulted in an increase in serum apolipoprotein A-II levels and a reduction in serum apo C-III and apo E. VLDL subfractionation by density gradient centrifugation in four subfractions of decreasing size (A, B, C and D) showed a predominant reduction of the large subfractions A, B and C, while the decrease in VLDL-D was less marked. Percentage changes from the baseline level of VLDL-A and VLDL-D cholesterol were found to be inversely correlated with percentage changes in HDL and LDL cholesterol, respectively. This might reflect a transfer of cholesterol from VLDL-A to HDL, and from VLDL-D to LDL. The above data suggest fibrate-induced stimulation of lipoprotein lipase, and indicate that the enhanced transfer of cholesterol from VLDL to LDL, induced by fibrates in HTG patients, is less pronounced after a prolonged period of treatment.

Long-term effects of bezafibrate on in vivo VLDL-triglyceride production in the rat

Long-term effects of bezafibrate on in vivo production of VLDL-triglyceride were studied in the rat. Bezafibrate given at a daily dose of 30 mg/kg body weight for 14 days produced a decrease not only in triglyceride by 51% but in cholesterol by 28% and phospholipid by 18%. Despite a marked reduction in plasma triglyceride concentrations, there was no significant change in the rate of VLDL-triglyceride secretion from the liver into the circulation between bezafibrate-treated and control animals (1113 +/- 58 and 1234 +/- 63 micrograms/min, respectively). In addition, bezafibrate produced no change in lipid composition in VLDL. These results suggest that bezafibrate enhances triglyceride removal from the circulation, which leads to reduction in plasma triglyceride.