Lecithin: cholesterol acyltransferase activity in familial hypercholesterolemia treated with simvastatin and simvastatin plus low-dose colestipol

Apolipoprotein E genotype as a most significant predictor of lipid response at lipid-lowering therapy: mechanistic and clinical studies

APOE alleles and apolipoprotein E isoforms control plasma cholesterol level on population level. Among three ɛ2, ɛ3, ɛ4 alleles, ɛ4 allele is associated with the increase in cholesterol level, risk of atherosclerosis and Alzheimer disease, while ɛ2 allele is associated with the decrease in cholesterol level and risk of atherosclerosis. The increase in plasma triglyceride is an independent risk factor of atherosclerosis and triglyceride-high density lipoprotein coupling determines the efficiency of reverse cholesterol transport. The impairment of this coupling specifically at hypertriglyceridemia may be followed by specific lipoprotein markers. The influence of major lipid-lowering drugs on lipoprotein metabolism and association of apoE isoforms with the efficiency of therapy by statins and fibrates are summarized both at isolated and combined increase in plasma triglyceride and cholesterol. APOE polymorphism seems to be a single genetic variant with a confirmed stratification both at candidate gene and at wide genome analyses.

Clinical pharmacokinetics of 3-hydroxy-3-methylglutaryl-coenzyme A reductase inhibitors

3-Hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase is the key enzyme of cholesterol synthesis. HMG-CoA reductase inhibitors are potent reversible inhibitors of this enzyme, which act by competing for the substrate HMG-CoA. This review is mainly devoted to the 4 main HMG-CoA reductase inhibitors used today: lovastatin, simvastatin, pravastatin and fluvastatin. Depending upon the dosage, these drugs are able to reduce plasma cholesterol levels by more than 40%. After absorption, each undergoes extensive hepatic first-pass metabolism. Up to 5 primary metabolites are formed, some of which are active inhibitors. The elimination half-lives vary from 0.5 to 3.5 hours and excretion is mainly via the faeces. A limited number of drug interactions has been reported. Increases in liver enzymes and muscle creatine kinase activity are among the most severe adverse effects. These powerful drugs should be reserved for patients with high plasma cholesterol levels and/or those with cardiovascular disease. New therapeutic approaches to atherosclerosis are currently under investigation. HMG-CoA reductase inhibitors are the cornerstone of this research.

Simvastatin. A reappraisal of its pharmacology and therapeutic efficacy in hypercholesterolaemia

Simvastatin is an HMG-CoA reductase inhibitor used in the treatment of patients with hypercholesterolaemia. Since the time simvastatin was previously reviewed in Drugs, a number of large clinical trials have confirmed its clinical efficacy. Thus, reductions from baseline were approximately 20 to 40% for serum levels of total cholesterol, 35 to 45% for low density lipoprotein (LDL)-cholesterol and 10 to 20% for triglycerides in patients with primary hypercholesterolaemia receiving simvastatin 10 to 40 mg/day. High density lipoprotein (HDL)-cholesterol levels were increased modestly by about 5 to 15%. Recent data from long term studies indicate that little or no attenuation of these changes in serum lipid and lipoprotein levels occurred with administration of simvastatin for 3 to 5.4 years. Comparative studies with other HMG-CoA reductase inhibitors (lovastatin, pravastatin and fluvastatin), which were lacking at the time of the previous review of simvastatin, demonstrated greater reductions in serum levels of total cholesterol and LDL-cholesterol with simvastatin than equal dosages of lovastatin or pravastatin. Reductions in serum levels of total cholesterol and LDL-cholesterol were similar between agents only when lovastatin or pravastatin were administered at a total daily dosage twice that of simvastatin and when fluvastatin was administered at a total daily dosage approximately 8 times that of simvastatin. In general, simvastatin 10 to 40 mg/day was also more effective than standard dosages of bile acid sequestrants, fibrates or probucol in lowering serum levels of total cholesterol and LDL-cholesterol; however, fibrates usually produced greater reductions in serum triglycerides and greater elevations in HDL-cholesterol levels. The Scandinavian Simvastatin Survival Study (4S), a large secondary prevention study in patients with coronary heart disease and concomitant hypercholesterolaemia, demonstrated that simvastatin 20 to 40 mg/day for a median of 5.4 years significantly reduced overall mortality (the primary end-point of the study) by 30% compared with placebo, which was attributed to a 42% relative reduction in coronary mortality. Coronary morbidity was also significantly reduced by simvastatin in the 4S trial. The tolerability profile of simvastatin appears to be comparable to that of other HMG-CoA reductase inhibitors. The most frequently reported adverse events are gastrointestinal disturbances, which are generally mild and tend to occur less frequently than with cholestyramine. In conclusion, simvastatin is among the most effective agents available for treating patients with hypercholesterolaemia.(ABSTRACT TRUNCATED AT 400 WORDS)

Abnormal acyltransferase activities and accelerated cholesteryl ester transfer in patients with nephrotic syndrome

To determine the effects of the nephrotic syndrome (NS) on atherogenic risk, we studied the lipoprotein composition and the activities of lecithin-cholesterol acyltransferase (LCAT), lysolecithin acyltransferase (LAT), and cholesteryl ester transfer (CET) in the plasma of 11 NS patients and 10 control subjects. NS plasma had lower ratios of high-density lipoprotein (HDL) to low-density lipoprotein (LDL) and HDL2/HDL3 and an elevated free cholesterol (FC) to phosphatidyl choline (PC) ratio (1.09 +/- 0.27 in NS and 0.72 +/- 0.21 in controls, P < .02), all of which indicate an increased atherogenic potential. LCAT activity was normal in NS plasma when assayed with an exogenous substrate, but was 40% lower than in control plasma when assayed with the endogenous substrates. However, in vitro addition of serum albumin to NS plasma failed to normalize the LCAT activity. The LAT reaction, which is catalyzed by LCAT protein in the presence of LDL, was 60% to 80% higher in NS plasma, and consequently the ratio of LAT/LCAT activities was increased twofold. CET activity was significantly increased (+160% of control), and this abnormality was attributable to changes in both the acceptor (very-low-density lipoprotein [VLDL] + LDL) and donor (HDL) lipoproteins and possibly in CET protein. These results suggest that the NS may increase the risk of atherosclerosis not only by adversely affecting the concentrations of lipoproteins, but also by altering their composition and function.

Effects of celiprolol vs. nifedipine on serum lipoproteins in patients with mild to moderate hypertension

During a double-blind, randomized study in hypertensive patients, changes in plasma lipid and lipoprotein levels during treatment with celiprolol were compared with those occurring during nifedipine treatment. Fifty-three patients (28 men and 25 women) with mild-to-moderate hypertension, aged 20-64 years, were studied. After a 1-month placebo run-in period, patients were randomly assigned to receive either nifedipine (40 mg daily) or celiprolol (200 mg daily), each time using a double-dummy technique. After 6 weeks, dosages of each drug could be doubled. After 6 weeks, there were no differences in plasma lipids between the two treatment groups. However, the changes after 12 weeks of treatment were different (p < 0.05) between the groups, leading to lower levels of plasma esterified cholesterol, low-density lipoprotein (LDL) cholesterol, and apoprotein AI, AII, and B in the celiprolol group. Plasma lecithin cholesterol acyltransferase activity (LCAT) was not modified. The present study showed that celiprolol was at least equivalent to nifedipine in terms of secondary effects on plasma lipids and lipoprotein.

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.

Effects of combined bezafibrate-simvastatin appraised in healthy subjects

The occurrence of clinical and biochemical side effects of bezafibrate (400 mg daily) or simvastatin (20 mg daily) alone or combined was appraised in 13 healthy male normolipidemic subjects according to a single blind design. Each period of 2 weeks of treatment with bezafibrate or simvastatin or bezafibrate plus simvastatin was followed by a period of placebo (1 week). No subjects experienced myalgia or muscle weakness. Plasma creatine kinase (CK) elevations, particularly skeletal muscle CK (CK-MM), were observed in 6 subjects: 11 times during different placebo periods, 5 times on bezafibrate, 4 times on simvastatin, and 4 times on combined bezafibrate-simvastatin, but never reached 1,600 IU/L. Only a trend to an increase of CK mean values on combined bezafibrate-simvastatin was shown. The hepatic transaminase and gamma-glutamyltransferase activities remained unmodified throughout the trial, unlike alkaline phosphatase activity, which fell on bezafibrate and on bezafibrate plus simvastatin. The low-density lipoprotein cholesterol level was more reduced with simvastatin than with bezafibrate. The addition of bezafibrate to simvastatin did not decrease it further. Lecithin:cholesterol acyltransferase activity expressed as fractional esterification rate was enhanced only on simvastatin and bezafibrate-simvastatin.