Cholesterol reduction in cardiovascular disease. Clinical benefits and possible mechanisms

Lowering LDL cholesterol: questions from recent meta-analyses and subset analyses of clinical trial DataIssues from the Interdisciplinary Council on Reducing the Risk for Coronary Heart Disease, ninth Council meeting

The benefit of cholesterol-lowering therapy in the prevention of coronary heart disease (CHD) is well established. The secondary prevention Scandinavian Simvastatin Survival Study (4S) and the primary prevention West of Scotland Coronary Prevention Study (WOSCOPS) demonstrated that lipid lowering with a statin can dramatically and cost-effectively reduce CHD morbidity and mortality with no increase in noncardiovascular mortality. The Cholesterol and Recurrent Events (CARE) trial extended benefit to CHD patients without high cholesterol. Post hoc analyses of data from these large trials are contributing to speculation, driven by subset analyses and meta-analyses, about whether cholesterol intervention should be target based, as current guidelines recommend. Whereas CARE data support the importance of baseline LDL cholesterol (LDL-C), with greatest clinical event risk reduction in the upper part of the LDL-C range in the trial, 4S found no difference in outcome according to baseline LDL-C in a quartile analysis, and WOSCOPS found no linear relation between decrease in LDL-C and decrease in relative risk for CHD. Furthermore, WOSCOPS showed no additional clinical benefit with LDL-C lowering beyond approximately 24%. Questions raised by such analyses require answers from prospective, hypothesis-based data, and at present there is no compelling argument for moving away from LDL-C targets. The hypothesis-based findings of 4S, CARE, and WOSCOPS support current clinical guidelines, and lowering LDL-C may reduce risk more substantially than might have been predicted.

Zwitterionic Sulfobetaine Inhibitors of Squalene Synthase

A substantial number of sulfobetaines (e.g., 10) have been synthesized and evaluated as inhibitors of squalene synthase (SS) on the basis of the idea that their zwitterionic structure would have properties conducive both to binding in the active site and to passage through cell membranes. When the simple sulfobetaine moiety is incorporated into compounds containing hydrophobic portions like those in farnesyl diphosphate (1) or presqualene diphosphate (2), inhibition of SS in a rat liver microsomal assay was indeed observed. For example, farnesylated sulfobetaine 10 has IC(50) = 10 &mgr;M and aromatic derivative 35 has IC(50) = 2 &mgr;M for SS inhibition. A wide variety of structural modifications, exemplified by compounds 43, 52, 76, 85, 91, 99, 111, and 115, was investigated. Unfortunately, no inhibitors in the submicromolar range were discovered, and exploration of a different type of zwitterion seems necessary if this appealing approach to inhibition of SS is going to provide a potential antihypercholesterolemic agent.

A critical analysis of the role of cholesterol in atherogenesis

Serum hypercholesterolemia is theorized to accelerate atherogenesis by augmenting cholesterol accumulation (insudation) in the arterial intima. The author views this theory as an example of what the noted philosopher of science Imre Lakatos called 'degenerative science', because data have forced several modifications of the theory. Although the theory that some fraction of intimal cholesterol causes atherosclerosis is not yet disproved, the author favors the hypothesis that serum hypercholesterolemia accelerates atherogenesis and contributes to symptomatic atherosclerosis by increasing blood viscosity and the mechanical fragility of atherosclerotic plaques, making them vulnerable to rupture and thrombosis.

Results of an open, longitudinal multicenter LDL-apheresis trial

The German Multicenter LDL-Apheresis Trial showed that a partial regression of tendon xanthomas could be obtained applying LDL-apheresis without cholesterol lowering drug therapy over a period of 3 years, whereas secondary prevention of coronary heart disease was generally observed in the mainly heterozygous patients. As there were considerably fewer homozygous patients and the average age of the heterozygous patients in this study was higher compared to the phase I trial regression may well occur with this therapy although it appears to be restricted to young patients only. If the additional information obtained from continuation of the treatment these patients and from other patients under going regular LDL-apheresis for up to 16 years is also taken into consideration the assumption appears to be well supported that interventions such as a second PTCA or a second coronary bypass operation can be avoided. LDL-apheresis increases the quality of live by decreasing the frequency of angina pectoris and also--at least in homozygous patients--is able to prolong life expectancy to a considerable extent. However, additional risk factors may play a role and have to be taken into consideration.

Effect of HMG-CoA reductase inhibitors on coronary artery disease as assessed by electron-beam computed tomography

BACKGROUND

Angiographic studies of the regression of coronary artery disease are invasive and costly, and they permit only limited assessment of changes in the extent of atherosclerotic disease. Electron-beam computed tomography (CT) is noninvasive and inexpensive. The entire coronary-artery tree can be studied during a single imaging session, and the volume of coronary calcification as quantified with this technique correlates closely with the total burden of atherosclerotic plaque.

METHODS

We conducted a retrospective study of 149 patients (61 percent men and 39 percent women; age range, 32 to 75 years) with no history of coronary artery disease who were referred by their primary care physicians for screening electron-beam CT. All patients underwent base-line scanning and follow-up assessment after a minimum of 12 months (range, 12 to 15), and a volumetric calcium score was calculated as an estimate of the total burden of plaque. Treatment with 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors was begun at the discretion of the referring physician. Serial measurements of low-density lipoprotein (LDL) cholesterol were obtained, and the change in the calcium-volume score was correlated with average LDL cholesterol levels.

RESULTS

One hundred five patients (70 percent) received treatment with HMG-CoA reductase inhibitors, and 44 patients (30 percent) did not. At follow-up, a net reduction in the calcium-volume score was observed only in the 65 treated patients whose final LDL cholesterol levels were less than 120 mg per deciliter (3.10 mmol per liter) (mean [+/-SD] change in the score, -7+/-23 percent; P=0.01). Untreated patients had an average LDL cholesterol level of at least 120 mg per deciliter and at the time of follow-up had a significant net increase in mean calcium-volume score (mean change, +52+/-36 percent; P<0.001). The 40 treated patients who had average LDL cholesterol levels of at least 120 mg per deciliter had a measurable increase in mean calcium-volume score (25+/-22 percent, P<0.001), although it was smaller than the increase in the untreated patients.

CONCLUSIONS

The extent to which the volume of atherosclerotic plaque decreased, stabilized, or increased was directly related to treatment with HMG-CoA reductase inhibitors and the resulting serum LDL cholesterol levels. These changes can be determined noninvasively by electron-beam CT and quantified with use of a calcium-volume score.

Carotid intima-media thickness and plaque in patients with familial hypercholesterolaemia mutations and control subjects

BACKGROUND

In individuals with familial hypercholesterolaemia (FH), ultrasonographic measurement of carotid intima-media thickness (IMT) and plaque may provide a non-invasive assessment of cardiovascular risk.

METHODS

We examined carotid artery IMT and its determinants in 79 non-smoking, normotensive, treated men and women with FH aged 26-46 years, and in 79 non-smoking, normotensive sex-, age- and body mass index-matched control subjects. FH was verified by molecular genetic analyses. The underlying mutation in the low-destiny lipoprotein receptor gene included a splice-site mutation, mutations predicted or shown to lead to class 2B mutations or other mutations that probably represent class I mutations (null alleles).

RESULTS

The carotid bifurcation and common carotid artery IMT was increased in men with FH compared with control subjects (0.81 +/- 0.15 mm vs. 0.74 +/- 0.19 mm and 0.61 +/- 0.13 mm vs. 0.55 +/- 0.14 mm respectively; P < 0.05). The carotid bifurcation IMT was increased in women with FH compared with control subjects (0.74 +/- 0.17 vs. 0. 66 +/- 0.15; P = 0.005). More subjects with FH had carotid plaque (54% vs. 14%; P = 0.0001). In multivariate analysis, male gender, level of low-density lipoprotein-cholesterol, cholesterol-years score and xanthoma were associated with IMT and plaque in subjects with FH. FH subjects with class 2B mutations had lower cholesterol levels than subjects with mutations belonging to the other classes. They also had a tendency towards a decreased common carotid artery IMT.

CONCLUSION

These findings confirm the importance of gender, xanthoma and lifetime cholesterol levels in relation to carotid atherosclerosis in FH. Whether the type of mutation causing FH modulates carotid artery IMT and plaque requires further study.

Infection and atherosclerosis--focus on cytomegalovirus and Chlamydia pneumoniae

BACKGROUND AND OBJECTIVE

Numerous studies have reported an association of coronary atherosclerosis and restenosis with certain bacterial and viral infections. This article reviews the pathophysiology of atherosclerosis, the role of infectious agents (i.e, cytomegalovirus and Chlamydia pneumoniae) in atherogenesis, and studies supporting the potential beneficial effects of antibiotics or antiviral agents in the management of atherosclerotic disease.

DATA SOURCES

English-language clinical studies, abstracts, and review articles pertaining to infectious agents and coronary atherosclerosis.

STUDY SELECTION AND DATA EXTRACTION

Relevant seroepidemiologic and pathologic studies and animal models evaluating the role of cytomegalovirus or C. pneumoniae in coronary atherosclerosis.

DATA SYNTHESIS

Studies evaluating the possible role of cytomegalovirus and C. pneumoniae in the pathogenesis of atherosclerosis, as well as studies examining the use of antimicrobial and antiviral agents for reduction of cardiovascular events, are reviewed and critiqued.

CONCLUSIONS

Current data do not allow us to determine whether infection is a cause or a cofactor of atherosclerosis. These uncertainties can be resolved by larger scale seroepidemiologic, pathologic, and interventional studies. Such efforts will contribute to identifying populations that are appropriate for particular surveillance or specific interventions, such as antibiotics or antiviral therapy.

Kinetics of triglyceride rich lipoproteins: chylomicrons and very low density lipoproteins

Lipoprotein dynamics are complex during the postprandial state. A significant rise in chylomicron concentration is associated with increased competition for LPL with VLDL particles. This results in an increased concentration of large VLDL. The concentration of small VLDL is reduced as a result of diminished conversion of large to small VLDL. Such changes, induced in the postprandial state, complicate the application and development of models that describe lipoprotein particle kinetics. The development of models that integrate chylomicron and VLDL particle information, rather than surrogate markers, together with data including other variables will provide insight into the complexity of lipoprotein metabolism in the postprandial state.

How to standardize vasomotor tone in serial studies based on quantitation of coronary dimensions?

In patients with coronary artery disease including those after coronary bypass graft operation and heart transplantation intervention studies based on serial quantitative coronary angiography, in part combined with intravascular ultrasound, are of increasing relevance. Since vasomotor tone of epicardial coronary arteries is influenced by a variety of factors, angiographic follow-up studies require standardization of coronary tone by induction of maximal dilation. We reviewed the effects of the most potent coronary vasodilatory drug groups, calcium antagonists and nitrocompounds, on coronary diameters. Intravenous or intracoronary injections of verapamil, diltiazem, nifedipine, nicardipine, and nisoldipine can cause profound coronary dilation which has been shown to be maximal with verapamil and nisoldipine. Shortcomings of calcium antagonists include short or unknown duration of action after bolus administration, severe drop in blood pressure, and lack of commercial availability of solutions for injection of many substances. Isosorbide dinitrate induces profound coronary dilation; however, after sublingual administration marked blood pressure decrease can occur, and the duration of action and ideal dose of intracoronary isosorbide dinitrate has not been investigated yet. Injections of molsidomine and its active metabolite, SIN-1, cause longlasting, reproducible, maximal coronary dilation, although only after a waiting period of at least 10 minutes; unfortunately, SIN-1 is only commercially available in France. Nitroglycerin induces reproducible maximal coronary dilation and is easy to administer sublingually or as intracoronary bolus injection with rapid onset of action and no major side effects. The short duration of action may require repeated administrations. To date, repeated intracoronary bolus injections of 0.1 mg nitroglycerin every 10 minutes seem to be the optimal known regimen for standardization of coronary vasomotor tone in serial angiographic studies. Further investigations in this field with old and new vasodilatory drugs are recommendable.

Need for a paradigm shift: the importance of risk factor reduction therapy in treating patients with cardiovascular disease

Cardiovascular disease remains the number one killer in the United States, despite advances made in diagnosis and therapy. A major shift to expand treatment beyond symptomatic obstructions and infarctions toward comprehensive therapies aimed at treatment of the underlying disease process could decrease the death rate and cost of cardiovascular disease enormously. In the past 5 years, major trials have clearly demonstrated that aggressive intervention with lipid-lowering therapy can dramatically alter the course of disease. Aspirin, smoking cessation, exercise, diet, and other medical and lifestyle interventions can also decrease risk. Successful therapies are not being implemented, however. Making prevention the primary approach to treatment will require increased resource allocation, use of health provider teams, integration of healthcare delivery systems, and expanded emphasis on educating patients about prevention.

The antiatherogenic role of high-density lipoprotein cholesterol

Landmark clinical studies in the past 5 years that demonstrated diminished mortality and first coronary events following lowering of low-density lipoprotein (LDL) cholesterol stimulated considerable interest in the medical community. Yet, high-density lipoprotein (HDL) cholesterol, which transports circulating cholesterol to the liver for clearance, clearly also exerts antiatherogenic effects. The Framingham Heart Study produced compelling epidemiologic evidence indicating that a low level of HDL cholesterol was an independent predictor of coronary artery disease (CAD). Emerging experimental and clinical findings are, collectively, now furnishing a solid scientific foundation for this relation. First, the reverse cholesterol transport pathway--including the roles of nascent (pre-beta) HDL, apolipoprotein A-I, lecithin-cholesterol acyltransferase (LCAT), cholesteryl ester transport protein, and hepatic uptake of cholesteryl ester from HDL by liver--is better understood. For example, the identification of a hepatic HDL receptor, SR-BI, suggests a mechanism of delivery of cholesteryl ester to liver that differs from the receptor-mediated uptake of LDL. Second, apolipoprotein A-I, the major protein component of HDL, and 2 enzymes on HDL, paraoxonase and platelet-activating factor acetylhydrolase appear to diminish the formation of the highly atherogenic oxidized LDL. Third, lower levels of HDL cholesterol are associated in a dose-response fashion with the severity and number of angiographically documented atherosclerotic coronary arteries. Fourth, low HDL cholesterol predicts total mortality in patients with CAD and desirable total cholesterol levels (<200 mg/dL). Fifth, low HDL cholesterol concentrations appear to be associated with increased rates of restenosis after percutaneous transluminal coronary angioplasty. In terms of elevating HDL cholesterol, cessation of cigarette smoking, reduction to ideal body weight, and regular aerobic exercise all appear important. Most medications used to treat dyslipidemias will raise HDL cholesterol levels modestly; however, niacin appears to have the greatest potential to do so, and can increase HDL cholesterol up to 30%. Recognizing these data, the most recent report of the National Cholesterol Education Program identified low HDL cholesterol as a CAD risk factor and recommended that all healthy adults be screened for both total cholesterol and HDL cholesterol levels.

Ascorbate prevents the interaction of superoxide and nitric oxide only at very high physiological concentrations

The bioactivity of nitric oxide (.NO) depends, in part, on its interaction with superoxide. Usually, superoxide dismutase (SOD) preserves .NO bioactivity by limiting the availability of superoxide. Ascorbic acid also effectively scavenges superoxide, but the extent to which this interaction is necessary for intact .NO bioactivity is not known. Therefore, the present study examined the effect of ascorbic acid on .NO bioactivity with isolated rabbit arterial segments. A steady flux of superoxide (1.15 to 2.3 micromol . L-1 . min-1) produced either by pyrogallol autoxidation or a hypoxanthine/xanthine oxidase system inhibited endothelium-derived .NO-mediated arterial relaxation elicited by acetylcholine. This effect of superoxide was completely blocked by SOD (300 IU/mL) and the manganese SOD mimic EUK-8 (300 micromol/L) and partially inhibited by ascorbic acid (10 mmol/L). Lower concentrations of ascorbic acid were ineffective despite scavenging >90% of superoxide. We increased the endogenous flux of superoxide (3.2+/-0.3-fold) by inhibiting vascular copper-zinc SOD with diethyldithiocarbamate. This increased endogenous flux of superoxide produced an impairment of .NO-mediated arterial relaxation that was reversed by EUK-8 (300 micromol/L) but not ascorbic acid (10 mmol/L) despite equivalent scavenging of the endogenous superoxide flux. We used 3-nitrotyrosine formation (from peroxynitrite) as an indicator of .NO interaction with superoxide and found that SOD and EUK-8 compete more effectively with .NO for superoxide than does ascorbic acid. These data indicate that preservation of .NO bioactivity by superoxide scavengers depends not only on superoxide scavenging activity, but also on the rate of superoxide scavenging. Normal extracellular concentrations of ascorbic acid (30 to 150 micromol/L) are not likely to prevent the interaction of .NO with superoxide under physiological conditions.

Serum lipid physiology and the influence of glaucoma medications

Understanding the effect of serum lipid levels on risk factors for coronary heart disease and how they are influenced by medical therapy may lead to overall better care of the glaucoma patient. Elevated low-density lipoprotein and total cholesterol levels are major risk factors for heart disease. In contrast, high-density lipoprotein (HDL) is protective for heart disease. beta-adrenergic blockers, a class of medicines used to treat glaucoma, may influence serum lipid levels. Oral nonselective beta-adrenergic blockers reduce HDL cholesterol by 19% and increase triglycerides by 20-40%. Furthermore, topical nonselective beta-adrenergic blockers also decrease serum HDL and worsen the total cholesterol/HDL ratio. However, beta-blockers with intrinsic sympathomimetic activity appear to be lipid neutral. At present, there is no clear clinical evidence to indicate that changes in serum lipids with use of topical beta-adrenergic blockers significantly affect the clinical course of the patient. Little information is available for other classes of medicines used topically to treat glaucoma. However, oral preparations of prostaglandins, alpha-adrenergic agonists, angiotensin-converting enzyme inhibitors, and calcium channel blockers do not adversely affect serum lipid levels. Further study is required on newer glaucoma preparations to determine their specific actions on lipid levels. Additionally, further work is required to understand the significance of not only the adverse effect of beta-adrenergic blockers on lipid levels, but their overall effect on long-term cardiac morbidity and mortality.

Dyslipoproteinaemia and hyperoxidative stress in the pathogenesis of endothelial dysfunction in non-insulin dependent diabetes mellitus: an hypothesis

Endothelial dysfunction in non-insulin dependent (Type 2) diabetes mellitus (NIDDM) has implications for the pathogenesis of the two major complications, macrovascular disease and microangiopathy. Endothelial dysfunction is a consequence of a disturbance in the L-arginine/nitric oxide pathway. Its occurrence in NIDDM is well supported by both in vitro and in vivo studies. NIDDM results in diverse abnormalities in lipoprotein metabolism, the most significant being hypertriglyceridaemia which is associated with increased plasma concentrations of small dense LDL and low levels of HDL. Dysglycaemia results in hyperoxidative stress and increased formation of advanced-glycosylation endproducts, both of which enhance the oxidative modification of lipoprotein particles. Based on extensive in vitro studies and on human data, we generate the hypothesis that the development of endothelial dysfunction in NIDDM is a consequence of the effect of dyslipoproteinaemia, in particular increased circulatory concentrations of modified small dense LDL and of hyperoxidative stress on the formation, action and disposal of nitric oxide, by diverse molecular mechanisms; HDL is proposed to have a protective effect on these processes through its enzymic antioxidant properties. The hypothesis proposed is simple, testable and consistent with wide sources of evidence. The practical implications of the hypothesis and the existing opportunities for the prevention and reversal of endothelial dysfunction in NIDDM are also reviewed and discussed.

Concentration of endogenous tPA antigen in coronary artery disease: relation to thrombotic events, aspirin treatment, hyperlipidemia, and multivessel disease

Tissue plasminogen activator (tPA) is the major plasminogen activator responsible for dissolving blood clots found in blood vessels. However, elevated concentrations of tPA antigen were found to be related to adverse events in patients with coronary artery disease (CAD). Considerable controversy about the significance of these results exists. The goal of this cross-sectional study was to identify independent determinants for tPA antigen concentrations in patients with CAD, to possibly clarify the above paradoxical relationship. The baseline tPA antigen concentrations of 366 patients with angiographic evidence of coronary sclerosis were determined. Univariate analysis showed that age (P=0.013), angiographic extent of disease (P<0.001), presence of angina at rest (P<0.001), diabetes mellitus (P=0.004), hypercholesterolemia (P=0. 045), hypertriglyceridemia (P=0.015), and chronic intake of nitrates (P<0.001) were significantly and positively related to tPA antigen concentration, while the chronic intake of aspirin was inversely related to tPA antigen (P<0.001). In addition, plasminogen activator inhibitor type 1 (PAI-1) activity was found to be significantly and positively associated with tPA antigen concentration (P<0.001). A multivariate analysis identified chronic low-dose aspirin therapy (P<0.001), PAI-1 activity (P<0.001), hypertriglyceridemia (P=0.005), the type of angina (P=0.026), multivessel disease (P=0.041), and hypercholesterolemia (P=0.043) as significant and independent determinants of tPA antigen. While hypertriglyceridemia and hypercholesterolemia both are related to the underlying disease, the type of angina and the number of involved vessels are linked to the severity and extent of disease, and all of them are indicators of a prothrombotic state found during the progression of CAD. In contrary, low-dose aspirin rather would decrease the likelihood of thrombotic events. The relation of tPA antigen to PAI-1 activity furthermore underlines the relation between tPA antigen concentration and a prothrombotic state. Therefore, the positive or-in case of aspirin therapy-negative correlation of these parameters with tPA antigen concentration would indicate that thrombus formation and simultaneous endothelial cell activation might be major determinants for tPA antigen concentration in CAD.

Contemporary Practice: Treatment Gap in Lipid-Lowering Therapy

Pharmacists can play a key role in preventing many adverse sequelae from improperly treated hypercholes-terolemia through treatment and monitoring strategies. Simvastatin and lovastatin utilization in an outpatient population was evaluated in this retrospective chart review. A dose-response effect for total cholesterol reduction was observed. Only 33% (13/40) of patients achieved consensus National Cholesterol Education Program (NCEP) therapy goals. Of those not meeting NCEP guidelines, 11% (3/27) were on maximum doses. Dosage adjustment occurred for 56% (15/27) but 27% (4/15) had no follow-up level. These results suggest that more aggressive lipid-lowering treatment and monitoring are necessary if guidelines are to be met.

Future of lipid-lowering trials: what else do we need to know?

Convincing clinical trial evidence shows that lipid-lowering therapy can be effective in primary and secondary prevention of coronary artery disease events. At least 2 studies indicate that this benefit extends to persons with only mild or moderate hypercholesterolemia. The benefits of lipid-lowering therapy in certain subpopulations, however, remains to be elucidated. The effects in women, African Americans, the elderly, and patients with concomitant coronary artery disease risk factors such as diabetes and hypertension are only recently being studied in large, well-designed trials. Other trials, described herein, are studying the benefits of therapy in persons with coronary artery disease and low levels of high-density lipoprotein (HDL) cholesterol (but normal or only mildly elevated total or low-density lipoprotein [LDL] cholesterol). Future trials are needed to assess prospectively the value of aggressive lipid-lowering therapy on coronary artery disease events in diabetic patients with and without coronary artery disease. New drug therapies and innovative uses for existing therapies are being developed that may have an important impact on the prevention of coronary artery disease.

Preclinical review of cerivastatin sodium--a step forward in HMG-CoA reductase inhibition

Epidemiological studies have established that elevated concentrations of plasma cholesterol, particularly the low density lipoprotein (LDL) cholesterol, is one of the major risk factors for the development of arteriosclerosis and ischemic heart disease. Treatment with HMG-CoA reductase inhibitors (vastatins) has become the most successful drug treatment in lowering total plasma and LDL cholesterol concentrations in the last years. The vastatins already available for treatment are therapeutically used in a dose-range between 10 and 80 mg/day. The new enantiomerically pure pyridine derivative cerivastatin sodium has demonstrated its efficacy in significantly lower doses in the microgram-range, not only in preclinical but also in clinical studies with daily doses of only 0.1-0.3 mg. The differences in the therapeutic doses are reflected by the Ki- and IC50-values from enzyme inhibition tests in comparison with various HMG-CoA reductase inhibitors. Cerivastatin sodium exhibits much higher enzyme affinity with factors between 70 and almost 200. The Ki-value for cerivastatin sodium was 1.3 x 10(-9) M in comparison to 150 x 10(-9) M for lovastatin. The extremely high enzyme affinity of cerivastatin sodium was also reflected in its high activity in vivo. In acute in vivo studies cerivastatin sodium inhibited the hepatic [14C]cholesterol synthesis from [14C]acetate in both rats and dogs by 50% after oral administration at doses of 0.002 mg/kg body weight (ED50-values). This dose was comparable to 0.3 mg/kg of lovastatin. In subchronic dog studies a dose of 0.03 mg/kg lowered the serum LDL cholesterol concentration by 35% which is comparable with doses of 8-10 mg lovastatin/kg. Interesting results were observed in cholestyramine-primed dogs when 0.1 mg cerivastatin sodium/kg p.o. markedly decreased the serum triglycerides up to 70%. Cerivastatin shows a favourable pharmacokinetic profile with high liver selectivity. Rat studies have shown almost complete absorption and rapid hepatic clearance. Cerivastatin was highly bound to plasma proteins of rats, dogs and humans (>98%). Cerivastatin metabolites were excreted mainly via feces. The metabolism of cerivastatin sodium in man follows two metabolic pathways, demethylation to metabolite M1 and stereospecific hydroxylation to M23. The three major metabolites M1, M23 and the hydroxylated and demethylated metabolite M24 are highly active inhibitors not only in vitro but also in vivo. The human specific metabolites M23 and M24 inhibited the HMG-CoA reductase isolated from rat liver with the same potency as the parent compound cerivastatin sodium (IC50: 1.0-1.2 x 10(-9) M). M1 was slightly less active. Corresponding pharmacological activity was observed in vivo. M23 and M24 inhibited [14C]cholesterol synthesis from [14C]acetate in rat liver with ED50)-values between 0.001 and 0.002 mg/kg body weight which is similar to cerivastatin sodium and M1 exhibited an ED50-value of <0.006 mg/kg The strong inhibitory activity of these metabolites, in addition to cerivastatin's high enzyme affinity may explain the extraordinary pharmacological activity of cerivastatin and its ultra-low dose in man and demonstrates cerivastatin to be the most active HMG-CoA reductase inhibitor amongst all vastatins.

Association between coronary angiograms and cardiac events--a prospective 3-year follow-up. INTACT-Investigators. International Nifedipine Trial on Antiatherosclerotic Therapy

The correlation between extent and severity of coronary artery disease as documented by quantitative coronary angiography and the incidence of cardiac events within 3 years was analyzed from a prospective study. In 73 out of 419 patients, 89 events occurred comprising 10 cardiac deaths, 15 non-fatal myocardial infarcts, 26 cases of unstable angina, and 38 coronary revascularization procedures (bypass graft operation or angioplasty). The incidence of any event correlated with the baseline number of all stenoses and high-grade stenoses (> or =20% and > or =50% diameter stenosis, respectively) (P<0.05). With respect to specific events, non-fatal myocardial infarcts and revascularization procedures were correlated with the number of all stenoses (P<0.05), but not with high-grade stenoses. Specification of coronary arteries revealed correlation of non-fatal myocardial infarcts and revascularization procedures with the number of high-grade stenoses in the left anterior descending artery. Finally, baseline left ventricular ejection fraction was found to be lower in patients who died of cardiac causes than in the remaining patients (49 +/- 10% vs. 67 +/- 13%; P<0.001). In conclusion, the total coronary stenosis burden seems to predict the incidence of subsequent cardiac events even better than the number of high-grade stenoses. Only in the left anterior descending artery high-grade stenoses seem to cause myocardial infarcts within a relatively short period of time justifying short-term revascularization in these patients.

Landmark trials in lipid reduction

Since the first epidemiological evidence on the benefit of lipid reduction in coronary heart disease (CHD) was gathered, a number of questions have emerged in this field of research. Consistent findings across a number of landmark trials have shown that lipid-lowering therapies significantly reduced major subsequent cardiovascular events in coronary patients with high and moderate low density lipoprotein (LDL) blood cholesterol levels. Although there has been some confusion on the effect of lipid intervention on mortality, recently definite answers have come from several major trials that establish a clear decrease in coronary death for patients after reduction of plasma cholesterol levels. Primary prevention in individuals with high LDL cholesterol levels was shown to be beneficial in terms of cardiovascular event reduction; more data are needed to address this issue for subjects with moderate LDL cholesterol levels. Reduction of LDL cholesterol below normal levels appeared to be beneficial for coronary patients, but again, further research is needed to elucidate this point. To date, major trials have answered some of the many questions pertaining to lipid-lowering therapies; further research will continue to provide information and allow patients to benefit maximally from lipid interventions.

Early endothelial dysfunction in adults at risk from atherosclerosis: different responses to L-arginine

OBJECTIVES

We sought to examine endothelial responses to L-arginine in three groups with isolated risk factors: hypercholesterolemia, smoking and insulin-dependent diabetes mellitus (IDDM).

BACKGROUND

Endothelial dysfunction occurs early in atherosclerosis, predating clinical disease. We hypothesized that the nature of endothelial injury associated with individual cardiovascular risk factors might be different and that this might affect the response to L-arginine, the substrate for endothelial nitric oxide synthase.

METHODS

We studied the effects of intravenous L-arginine on brachial artery flow-mediated dilation (FMD) and glyceryl trinitrate (GTN)-mediated dilation in 36 young subjects (18 to 40 years old) without clinical atherosclerosis: 9 each of normal control subjects, hypercholesterolemic subjects, cigarette smokers and subjects with IDDM.

RESULTS

Baseline FMD was significantly impaired in hypercholesterolemic subjects (mean +/- SD 1.7 +/- 2.3%), smokers (1.6 +/- 1.8%) and diabetic subjects (1.8 +/- 1.5%) compared with that in control subjects (6.9 +/- 3.3%, p = 0.001). The response to GTN was not significantly different between the subjects with risk factors and control subjects, apart from those with IDDM, in whom it was significantly impaired (p = 0.026). After infusion of L-arginine, there was no change in FMD in control or diabetic subjects. In hypercholesterolemic subjects and smokers, FMD improved from 1.9 +/- 1.9% to 4.1 +/- 2.1% (p = 0.01) and from 2.0 +/- 1.71% to 3.1 +/- 2.5% (p = 0.02), respectively.

CONCLUSIONS

FMD was impaired in all three risk factor groups; however, they responded differently to L-arginine, FMD being improved in hypercholesterolemic subjects and smokers but unchanged in diabetic subjects. These results indicate differing underlying pathophysiologies that may facilitate the design of treatment strategies for subjects with different risk factors.

Early cyclosporine monotherapy in liver transplantation: a 5-year follow-up of a prospective, randomized trial

Maintenance of adequate immunosuppression and avoidance of side-effects are the goals of long-term management of all organ-transplanted patients. We here report the final results of a prospective, randomized trial comparing early cyclosporine monotherapy versus double-drug therapy (cyclosporine and steroids) in adult liver transplantation patients. One hundred four patients were randomized 3 months after transplantation either to continue (Group I = 50 patients) or to stop steroids (Group II = 54 patients). Patients on a double-drug regimen were maintained long term on methylprednisolone at a dose of 0.1 mg/kg/d. Target cyclosporine trough levels were between 150 and 250 ng/mL in both groups. Our main points of interest were the prevalence of acute and chronic rejections and steroid-related side-effects in the two groups of patients. Mean follow-up was 41 +/- 16 months (range, 4-68 months). Patient actuarial survival 2 and 5 years after randomization was similar in the two groups (82% vs. 83% and 82% vs. 77%). The prevalence of acute rejections after randomization was, respectively, 8% and 4%. A single episode of chronic rejection was observed only in a patient on long-term steroid therapy. Side-effects of steroid therapy were less frequent in patients weaned off steroids, and when considering hypertension and diabetes, the differences between the two groups were statistically significant. Early cyclosporine monotherapy is a safe undertaking in liver transplantation because it allows a significant reduction of steroid-related side-effects without increasing the risk of acute and chronic rejection. After 5 years, patient survival was similar in patients with or without steroids.

The atherogenic lipoprotein phenotype and vascular endothelial dysfunction

There is accumulating evidence that elevated plasma triglycerides and related abnormalities constitute an independent cardiovascular risk factor. Although the pathogenetic basis for the apparent relationship between elevated triglyceride-rich lipoproteins and CAD is still uncertain, evidence is accumulating to suggest that endothelial dysfunction is involved. There is evidence to suggest that triglyceride-rich particles may be directly damaging to the endothelium; this may be principally via oxidative mechanisms. Triglyceride-rich particles can cross the endothelial barrier and enter the arterial wall, thus placing them in a position to promote direct endothelial damage. These particles stimulate endothelial expression of adhesion molecules and the prothrombotic factor PAI-1. By reducing LDL size and HDL cholesterol concentrations, thereby further increasing the endothelial oxidative burden, triglyceride-rich particles may indirectly promote endothelial dysfunction. In addition, free fatty acids, which are the major substrates for endogenous synthesis of triglyceride-rich particles, are also potentially damaging to the endothelium. This occurs via oxidative stress, by facilitating transfer of LDL across the endothelium, and by enhancing toxicity of triglyceride-rich particles. Finally, there is recent strong evidence to suggest that increased postprandial circulating concentrations of triglyceride-rich particles and remnant particles may be deleterious to the endothelium.

Diet and cardiovascular disease prevention: what works?

Diet is routinely recommended as the primary strategy for the prevention and treatment of high blood cholesterol. The National Cholesterol Education Program (NCEP), the American Heart Association (AHA), and a host of other health and medical organizations have advocated a diet low in total and saturated fat and cholesterol for reducing risk of cardiovascular disease. What is the evidence supporting these guidelines and the expected efficacy of dietary treatment? There is growing awareness that despite well-documented rationale for the dietary approach, many eligible patients are not routinely prescribed dietary treatment, and among those who are, there is limited response. What are the obstacles in implementing effective dietary intervention for prevention of cardiovascular disease? What are both the theoretical and practical limitations to achieving long-term adherence to diet and what strategies have been shown to be most effective? A review of the data surrounding these diet-lipid relationships is presented along with recently tested and promising behavioral approaches to facilitating patient adherence.

Perspectives in the treatment of dyslipidemias in the prevention of coronary heart disease

In this review the indications for the available treatments for dyslipidemias in the prevention of coronary heart disease (CHD) are considered, and their efficacy according to the latest studies is analyzed. As data sources the authors used the main multicenter studies performed in the last twenty years to evaluate primary and secondary prevention of CHD by correcting dyslipidemias as well as the results of meta-analyses of these studies. All treatments considered were found effective in preventing CHD morbidity and mortality to some extent. In particular, the combination of diet with niacin or hydroxymethylglutaryl coenzyme A (HMG CoA) reductase inhibitors seems to give the best results. These drugs induce a marked reduction of total and low-density lipoprotein (LDL) cholesterol and an increase of high-density lipoprotein (HDL) cholesterol concentrations. The use of diet, niacin, and HMG CoA reductase inhibitors reduces total as well as specific mortality. Treatment of dyslipidemia to prevent CHD depends on the pattern and severity of dyslipidemia, the presence of overt CHD, and the patient's response to diet. Pharmacologic treatment should be started only after dietary modifications have been tried and must be combined with diet. Drug side effects must also be considered, for they may affect patient compliance. High levels of total and LDL and low levels of HDL cholesterol are major risk factors for coronary atherosclerosis. Correcting lipid abnormalities can reduce the risk of development or progression of CHD. Diet and drugs are the main instruments available to normalize lipid levels. The choice of drug to combine with diet must be based on its specific effects on lipid metabolism, side effects, and efficacy in reducing CHD.

Low plasma ascorbic acid independently predicts the presence of an unstable coronary syndrome

OBJECTIVES

This study sought to investigate the relations between plasma antioxidant status, extent of atherosclerosis and activity of coronary artery disease.

BACKGROUND

Previous studies indicate that increased antioxidant intake is associated with decreased coronary disease risk, but the underlying mechanisms remain controversial.

METHODS

Plasma samples were obtained from 149 patients undergoing cardiac catheterization (65 with stable angina, 84 with unstable angina or a myocardial infarction within 2 weeks). Twelve plasma antioxidant/oxidant markers were measured and correlated with the extent of atherosclerosis and the presence of an unstable coronary syndrome.

RESULTS

By multiple linear regression analysis, age (p < 0.001), diabetes mellitus (p < 0.001), male gender (p < 0.001) and hypercholesterolemia (p = 0.02) were independent predictors of the extent of atherosclerosis. No antioxidant/oxidant marker correlated with the extent of atherosclerosis. However, lower plasma ascorbic acid concentration predicted the presence of an unstable coronary syndrome by multiple logistic regression (odds ratio [OR] 0.59, 95% confidence interval [CI] 0.40 to 0.89, p = 0.01). The severity of atherosclerosis also predicted the presence of an unstable coronary syndrome (OR 1.7, 95% CI 1.14 to 2.47, p = 0.008) when all patients were considered. When only patients with significant coronary disease were considered (at least one stenosis >50%), ascorbic acid concentration (OR 0.56, 95% CI 0.37 to 0.85, p = 0.008) and total plasma thiols (OR 0.52, 95% CI 0.34 to 0.80, p = 0.004) predicted the presence of an unstable coronary syndrome, whereas the extent of atherosclerosis did not.

CONCLUSIONS

These data are consistent with the hypothesis that the beneficial effects of antioxidants in coronary artery disease may result, in part, by an influence on lesion activity rather than a reduction in the overall extent of fixed disease.

L-2-Oxothiazolidine-4-carboxylic acid reverses endothelial dysfunction in patients with coronary artery disease

The effective action of endothelium-derived nitric oxide (EDNO) is impaired in patients with atherosclerosis. This impairment has been attributed in part to increased vascular oxidative stress. EDNO action is improved by administration of ascorbic acid, a water-soluble antioxidant. Ascorbic acid is a potent free-radical scavenger in plasma, and also regulates intracellular redox state in part by sparing cellular glutathione. We specifically investigated the role of intracellular redox state in EDNO action by examining the effect of L-2-oxo-4-thiazolidine carboxylate (OTC) on EDNO-dependent, flow-mediated dilation in a randomized double-blind placebo-controlled study of patients with angiographically proven coronary artery disease. OTC augments intracellular glutathione by providing substrate cysteine for glutathione synthesis. Brachial artery flow-mediated dilation was examined with high-resolution ultrasound before and after oral administration of 4.5 g of OTC or placebo in 48 subjects with angiographically documented coronary artery disease. Placebo treatment produced no change in flow-mediated dilation (7.0+/-3.9% vs. 7.2+/-3.7%), whereas OTC treatment was associated with a significant improvement in flow-mediated dilation (6.6+/-4.4% vs. 11.0+/-6.3%; P = 0.005). OTC had no effect on arterial dilation to nitroglycerin, systemic blood pressure, heart rate, or reactive hyperemia. These data suggest that augmenting cellular glutathione levels improves EDNO action in human atherosclerosis. Cellular redox state may be an important regulator of EDNO action, and is a potential target for therapy in patients with coronary artery disease.

[Therapeutic options for improvement of myocardial perfusion in coronary atherosclerosis]

The combination of morphological atherosclerotic alterations of coronary vessels and disturbance of coronary vasomotor control of epicardial and resistance vessels determines the amount of myocardial oxygen supply. The endothelium plays a crucial role for functional alterations of the coronary vessels in patients with early atherosclerosis or risk factors for coronary artery disease. A therapy which aims to ameliorate endothelium-dependent vasodilator capacity improves myocardial perfusion in patients with coronary artery disease. Thereby, even in patients with angiographically normal or minimally diseased coronary vessels who develop myocardial ischemia due to microvascular disease, symptomatic improvement might be achieved. Control of coronary vasomotor tone and proliferation processes within the vessel wall are both determined by the redox equilibrium of nitric oxide (NO) and superoxide radicals (O2-), induced by angiotensin II. Thus, vasomotor control and vessel wall proliferation is closely related to each other. Aim of a therapeutic intervention to enhance NO bioactivity is either to increase NO production in the endothelium or to decrease O2- production, which rapidly inactivates NO. NO bioactivity can be ameliorated by ACE-inhibitors, increase of shear stress on the endothelium by physical exercise, estrogens or L-arginine. For these therapies clinically an improvement of endothelial vasodilator function could be shown. In addition, improvement of endothelial vasodilator function can be achieved by a treatment which reduced oxidative stress in the vascular wall such as antioxidants and, especially, lipid lowering drugs. Endothelin-antagonists and angiotensin II receptor-blockers are promising to improve endothelial dysfunction. However, these therapies have to be validated. Most therapy strategies, which have shown to ameliorate endothelial dysfunction, are also able to improve prognosis of the patients. Whether endothelial dysfunction alone--without evidence of overt coronary atherosclerosis--is sufficient to justify a long-term therapy to improve prognosis, still has to be clarified.

Risk reduction therapies for patients with coronary artery disease: a call for increased implementation

Recent decades have witnessed significant advances in the use of interventional procedures and medical therapies for relief of symptoms associated with obstructive coronary artery disease (CAD). At the same time, however, little progress has been made in understanding and implementing preventive therapy and risk reduction. Our traditional focus on treatment of severe coronary obstruction has addressed only part of the problem. We now need to adopt a more comprehensive approach aimed at the entire spectrum of atherosclerotic disease. Numerous clinical trials have demonstrated that risk-reduction strategies can produce marked decreases in the incidence of cardiovascular events as well as in total mortality. Despite this strong body of evidence, risk-reduction therapies continue to be underutilized. Comprehensive changes in healthcare delivery systems are needed to ensure that risk-reduction strategies become a routine part of care for patients with cardiovascular disease.

Low-density lipoprotein apheresis using the Liposorber system: features of the system and clinical benefits

LDL apheresis using the Liposorber system is indicated for use to remove selectively LDL from the plasma of hypercholesterolemic patients for whom diet and maximum cholesterol-lowering drug therapy have been ineffective or not tolerated. The dextran sulfate immobilized to porous cellulose beads is contained in the adsorption column as the adsorbent. The dextran sulfate has a structure similar to that of the LDL receptor and seems to act as a type of pseudoreceptor for LDL. There have been reported a number of clinical benefits using the Liposorber system for drug refractory hypercholesterolemic patients. Among them, the improvement of endothelial cell function of coronary and brachial arteries by a single treatment is the focus of the world's attention. Moreover, it is also noteworthy that LDL apheresis reduced the incidence of the cardiac events by 70% compared to drug therapy alone. In addition to the clinical benefits of the Liposorber system on familial hypercholesterolemia (FH), the preliminary data suggest that LDL apheresis may improve arteriosclerosis obliterans (ASO) of the lower extremities and focal glomerular sclerosis (FGS).

Effects of Continuous and Cyclic Hormone Replacement Therapy on the Lipoprotein Profile in Postmenopausal Women

Objective:

To provide an overview of the information concerning cyclic and continuous hormone replacement therapy (HRT) and the effects of the various regimens on the lipid profile.

Data Sources:

MEDLINE (January 1966–December 1996) and Index Medicus (January 1995-December 1996) searches were conducted to identify relevant studies and review articles. Bibliographies of selected articles also were reviewed.

Study Selection:

Studies addressing continuous and cyclic use of a progesterone formulation along with daily conjugated equine estrogen (CEE) and their effects on the lipid profiles of postmenopausal women were selected for review.

Data Extraction:

Applicable data were selected and used in a review format.

Data Synthesis:

CEE has been shown to increase high-density-lipoprotein cholesterol, which may decrease the risk of cardiovascular heart disease. Medroxyprogesterone acetate (MPA) has been added to CEE for postmenopausal HRT to prevent endometrial hyperplasia and cancer. However, MPA negates the beneficial effects of CEE on the lipid profile. Many different HRT regimens, both continuous and cyclic, are being used to increase compliance and to decrease adverse effects. Which regimen offers the best lipid profile results is evaluated in this article.

Conclusions:

The lipid profile effects of HRT using continuous MPA are not significantly different from those obtained with cyclic MPA. Use of a continuous MPA regimen may also offer the long-term advantages of less vaginal bleeding and increased compliance.

Endothelial dysfunction and coronary risk reduction

There is growing evidence that improvement of endothelial function has the potential to reduce cardiovascular ris. This article reviews the impact of coronary risk factors on endothelial function and the benefits of risk factor reduction. Recent studies indicate that chronic exercise may directly improve endothelial function, thus providing an additional explanation for the benefits of increased physical activity.

Inhibition of 3-hydroxy-3-methylglutaryl (HMG)-CoA reductase blocks hypoxia-mediated down-regulation of endothelial nitric oxide synthase

Hypoxia induces vasoconstriction, in part, by down-regulating endothelial cell nitric oxide synthase (ecNOS) expression. Previous studies indicate that 3-hydroxy-3-methylglutaryl-coenzyme A (HMG CoA) reductase inhibitors improve endothelium-dependent relaxation by increasing ecNOS activity. To determine whether HMG CoA reductase inhibitors can prevent hypoxia-mediated down-regulation of ecNOS function and expression, human endothelial cells were exposed to hypoxia (3% O2) in the presence of HMG CoA reductase inhibitors simvastatin and lovastatin for various durations (0-48 h). Hypoxia decreased ecNOS protein and mRNA levels in a time-dependent manner, resulting in a 4- and 9-fold reduction after 48 h, respectively. In a concentration-dependent manner, simvastatin, and to a lesser extent, lovastatin, prevented the down-regulation of ecNOS expression by hypoxia. Simvastatin-induced changes in ecNOS expression correlated with changes in endothelial NO production and were reversed by treatment with L-mevalonate. Actinomycin D studies revealed that under hypoxic conditions, simvastatin increased ecNOS mRNA half-life from 13 to 38 h. Nuclear run-on studies showed that simvastatin had no effect on repression of ecNOS gene transcription by hypoxia. These results indicate that HMG CoA reductase inhibitors regulate ecNOS function and expression through changes in ecNOS mRNA stability and suggest that treatment with HMG CoA reductase inhibitors may have beneficial effects in patients with hypoxia-mediated pulmonary hypertension.

Current perspective on the use of angiotensin-converting enzyme inhibitors in the management of coronary (atherosclerotic) artery disease

OBJECTIVE

To review the pathophysiology of atherosclerosis, the role of the renin-angiotensin system in atherogenesis, and studies supporting the potential beneficial effects of angiotensin-converting enzyme (ACE) inhibitors in reducing cardiovascular events with long-term use.

BACKGROUND

Through its action in converting angiotensin I to angiotensin II and by degrading bradykinin, local tissue ACE exerts many effects that can contribute to the development of atherosclerosis. Therefore, the use of ACE inhibitors can possibly result in antiatherogenic effects. Possible mechanisms for antiatherogenic effects of ACE inhibitors include: (1) reduction of blood pressure; (2) antiproliferative and antimigratory effects on vascular smooth muscle cells, neutrophils, and monocytes; (3) restoration of endothelial function; (4) stabilization of fatty plaque by preventing vasoconstriction; (5) antiplatelet effects; and (6) enhancement of endogenous fibrinolysis.

DATA SOURCES

English-language clinical studies, abstracts, and review articles pertaining to the use of ACE inhibitors and atherosclerosis.

STUDY SELECTION AND DATA EXTRACTION

Relevant human studies examining the role of ACE inhibitors and atherosclerosis.

DATA SYNTHESIS

Studies evaluating the possible beneficial effects of ACE inhibitors in the development of atherosclerosis are reviewed and critiqued. Design of ongoing studies with clinical and surrogate end points are discussed.

CONCLUSIONS

Based on current published studies, recommendations are made regarding the use of ACE inhibitors in atherosclerosis. Therapeutic monitoring parameters for efficacy and adverse effects are also reviewed.

Endothelial cells prevent accumulation of lipid hydroperoxides in low-density lipoprotein

A variety of cell types, including endothelial cells, oxidize low-density lipoprotein (LDL). To investigate the mechanisms by which endothelial cells modulate LDL oxidation states, endothelial cell cultures were incubated with LDL (240 mg cholesterol/dL) for 24 hours in M199 supplemented with fetal bovine serum (FBS, 16.7%). These conditions were not toxic to endothelial cells over the time frame of the study. Changes in LDL oxidation were monitored by measuring thiobarbituric acid-reactive substances (TBARS), lipid hydroperoxide (LOOH), and conjugated dienes (A234nm). LDL medium incubated in the absence of endothelial cells contained higher TBARS than did LDL medium incubated with endothelial cells (0.35 +/- 0.08 versus 0.23 +/- 0.08 nmol MDA/mg, respectively). LOOHs were higher in LDL medium incubated without endothelial cells than in LDL medium incubated with endothelial cells (6.8 +/- 4.4 versus 0.49 +/- 0.89 nmol/mg, respectively). Conjugated diene formation, based on changes in absorbance at 234 nm, increased to a greater extent in LDL medium incubated in the absence of endothelial cells than when endothelial cells were present. To increase oxidative stress on the endothelial cell cultures, increasing concentrations of Cu2+ (0 to 4 mumol/L) were added to LDL medium. Endothelial cells prevented LOOH accumulation until the concentration of Cu2+ exceeded 0.75 mumol/L. At 1.5 and 4 mumol/L Cu2+, endothelial cells enhanced LOOH formation nearly 3 and 2.5 times the LOOH values in the corresponding medium incubated in the absence of endothelial cells. This loss of protective function however, was not permanent. Endothelial cells, preincubated for 24 hours with Cu(2+)-containing LDL medium, were still able to prevent LOOH accumulation in fresh LDL medium. Endothelial cells prevented LOOH accumulation even when exposed to LDL medium that contained low concentrations of LOOHs (< 22 nmol/mg). However, endothelial cells accelerated the accumulation of LOOHs in LDL when exposed to LDL medium that contained slightly higher concentrations of preexisting LOOHs (approximately equal to 33 nmol/mg). These data indicate that endothelial cells have a limited capacity for preventing LOOH formation and that small increases in LOOHs may play a critical role in enhancing the potential of endothelial cells for oxidative modification of LDL.

Cerivastatin: pharmacology of a novel synthetic and highly active HMG-CoA reductase inhibitor

The pyridine derivative cerivastatin is a new entirely synthetic and enantiomerically pure inhibitor of 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) reductase. As a sodium salt cerivastatin is present in the active, open ring form. Cerivastatin inhibited the membrane-bound (non-solubilized) HMG-CoA reductase of the native microsomal fraction isolated from rat liver with a Ki value of 1.3 x 10(-9) M. The reference compound lovastatin was 100-fold less potent and exhibited a Ki value of 150 x 10(-9) M. Cerivastatin inhibited the cholesterol synthesis in the human hepatoma cell line HepG2 cells with a similar IC50 value of 1.0 x 10(-9) M. In vivo studies reflected its high in vitro activity. In both rats and dogs, cerivastatin inhibited the hepatic [14C]cholesterol synthesis from [14C]acetate with an oral ED50 value of 0.002 mg/kg body weight, while lovastatin exhibited an oral ED50 value of 0.3 mg/kg in rats, showing again the ratio of 100 or more between cerivastatin and lovastatin. In the small intestine and testes, cerivastatin was at least 50-fold less active with oral ED50 values higher than 0.1 mg/kg, which is indicative for a high liver selectivity of cerivastatin. In cholestyramine-primed dogs cerivastatin dose-dependently lowered the serum cholesterol concentrations by up to 59% with 0.1 mg/kg after 20 days. Interestingly, the serum triglycerides were markedly reduced by 53 and 76% with 0.03 and 0.1 mg/kg, respectively. In normal chow fed dogs the low density lipoprotein (LDL) concentrations were reduced by up to 75% after 0.1 mg cerivastatin/kg. The ratio of HDL/LDL increased by 81% compared with a change of only 14% in the placebo treated control group. The antiatherogenic effect of cerivastatin was shown in rabbits fed a diet enriched with 0.2% cholesterol. After 9 weeks on diet 0.1 mg cerivastatin/kg decreased the accumulation of cholesterol ester in the arterial tissue by 73%. In summary, these data as compared to published data on other HMG-CoA reductase inhibitors demonstrate cerivastatin to be the most active compound in this class. Vastatins used in therapy are effective in mg doses, while cerivastatin offers a new low dose therapy in the microg range.

Vascular effects of statins in stroke

BACKGROUND

Recent clinical trials and meta-analyses of beta-hydroxy-beta-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors (statins) have demonstrated a reduction in ischemic stroke in patients with a history of coronary artery disease both with and without elevations of serum cholesterol. This review summarizes clinical trials of these compounds and their recent impact on stroke and explores the underlying vascular mechanisms of their actions.

SUMMARY OF REVIEW

Use of statins in patients with vascular disease has been shown to lower the incidence of stroke by approximately 30%. Statins exhibit a number of antiatherosclerotic and antithrombotic properties that likely underlie the recently observed reductions in cerebrovascular disease. Statins reduce inflammatory, proliferative, and thrombogenic processes in plaque, making it less likely to rupture. Additionally, they reverse the endothelial dysfunction and platelet activation accompanying hypercholesterolemia and may reduce the tendency to thrombosis.

CONCLUSIONS

Hypercholesterolemia has reemerged as a risk factor for ischemic stroke. Statins protect against thromboembolic stroke through multiple beneficial effects within the vascular milieu. Further data are awaited to support the growing importance of cholesterol as a risk factor for ischemic stroke and the benefits of statin therapy in patients with cerebrovascular disease.

Vascular superoxide dismutase deficiency impairs endothelial vasodilator function through direct inactivation of nitric oxide and increased lipid peroxidation

Nitric oxide (NO) and superoxide are both constitutive products of the endothelium. Because NO is readily inactivated by superoxide, the bioactivity of endothelium-derived NO (EDNO) is dependent on local activity of superoxide dismutase (SOD). We examined the effects of chronic inhibition of copper-zinc SOD (CuZnSOD) using a rat model of dietary copper restriction. Male weanling Sprague-Dawley rats were fed a Cu-deficient diet and received either no Cu replacement (Cu-deficient) or Cu in the drinking water (Cu-sufficient). Compared with Cu-sufficient animals, Cu-deficiency was associated with a 68% reduction in CuZnSOD activity and a 58% increase in vascular superoxide as estimated by lucigenin chemiluminescence (both P < .05). Compared with Cu-sufficient animals, arterial relaxation in the thoracic aorta from Cu-deficient animals was 10-fold less sensitive to acetylcholine, a receptor-dependent EDNO agonist, but only 1.5-fold less sensitive to A23187, a receptor-independent EDNO agonist, and only 1.25-fold less sensitive to authentic NO (all P < .05). In contrast, acute inhibition of CuZnSOD with 10 mM diethyldithiocarbamate produced a more uniform reduction in sensitivity to acetylcholine (8-fold), A23187 (10-fold), and NO (4-fold; all P < .001). Cu-deficient animals demonstrated a 2.5-fold increase in plasma-esterified F2-isoprostanes, a stable marker of lipid peroxidation, that correlated inversely with arterial relaxation to acetylcholine (R = -.83; P < .0009) but not A23187 or authentic NO. From these findings, we conclude that chronic inhibition of CuZnSOD inhibits EDNO-mediated arterial relaxation through two mechanisms, one being direct inactivation of NO and the other being lipid peroxidation that preferentially interrupts receptor-mediated stimulation of EDNO.

CLA-1 is an 85-kD plasma membrane glycoprotein that acts as a high-affinity receptor for both native (HDL, LDL, and VLDL) and modified (OxLDL and AcLDL) lipoproteins

Lipoprotein metabolism is regulated by the functional interplay between lipoprotein components and the receptors and enzymes with which they interact. Recent evidence indicates that the structurally related glycoproteins CD36 and SR-BI act as cell surface receptors for some lipoproteins. Thus, CD36 has been reported to bind oxidized LDL (OxLDL) and acetylated LDL (AcLDL), while SR-BI also binds native LDL and HDL. The cDNA of human CLA-1 predicts a protein 509 amino acids long that displays a 30% and an 80% amino acid identity with CD36 and mouse or hamster SR-BI, respectively. In this report, we describe the structural characterization of CLA-1 as an 85-kD plasma membrane protein enriched in N-linked carbohydrates. The expression of CLA-1 on mammalian and insect cells has been used to demonstrate that CLA-1 is a high-affinity specific receptor for the lipoproteins HDL, LDL, VLDL, OxLDL, and AcLDL. Northern blot analysis of the tissue distribution of CLA-1 in humans indicated that its expression is mostly restricted to tissues performing very active cholesterol metabolism (liver and steroidogenic tissues). This finding, in the context of the capability of this receptor to bind to both native and modified lipoproteins, strongly suggests that the CLA-1 receptor contributes to lipid metabolism and atherogenesis.

Altered compliance and residual strain precede angiographically detectable early atherosclerosis in low-density lipoprotein receptor deficiency

BACKGROUND

This study was performed to detect changes in vascular biomechanical properties early in atherogenesis.

METHODS AND RESULTS

Age- and weight-matched LDL-receptor deficient Watanabe hypercholesterolemic male rabbits (Group I: n = 11) and normal rabbits (Group II: n = 11) were studied. Fasting plasma lipoprotein concentrations, aortic angiography and intravascular ultrasound, in vivo aortic compliance evaluation, ex vivo aortic residual strain measurements, aortic lipid content and histopathology were determined. Plasma cholesterol was increased 9.8 fold and aortic cholesterol content was increased from 20 to 43 fold in Group I compared to Group II, respectively (P < .00005). Angiography revealed no stenoses in either group, whereas intravascular ultrasound and histological studies of Group I showed small circumferential plaques with < 10% cross-sectional area involvement. The residual strain in Group I was significantly increased in the ascending thoracic aorta (22.1 +/- 6.9% versus 10.4 +/- 3.2% in Group II, P < .0001), descending thoracic aorta (15.7 +/- 7.2% versus 4.8 +/- 1.3% in Group II, P < .0001), and abdominal aorta (18.0 +/- 4.8% versus 8.3 +/- 6.3% in Group II, P < .005). Changes in residual strain were inversely correlated with the aortic cholesterol content in the ascending thoracic aorta (r = -.72; P = -.001), descending thoracic aorta (r = -.95; P < .001), and abdominal aorta (r = -.51; P = .019).

CONCLUSIONS

Early atherosclerosis in LDL-receptor deficient rabbits, undetectable by angiography yet observed by intravascular ultrasound imaging and histology, is associated with marked changes in ex vivo residual strain. Alterations in vascular biomechanical properties, associated with changes in cholesterol content, may have physiologic consequences and may be useful in detecting and quantitating early atherosclerosis.

L-arginine for testing endothelium-dependent vascular functions in health and disease

The objective of this study was to assess the role of L-arginine, the natural precursor of nitric oxide, for testing endothelial function in physiological and pathophysiological conditions. In an initial study of 20 healthy subjects, mean blood pressure decreases in response to increasing doses of L-arginine (1, 2, 3, and 5 g) were 1.1 +/- 1.3, 2.6 +/- 1.5, 7.6 +/- 1.3, and 7.7 +/- 2 mmHg, respectively, P < 0.01. The enantiomer D-arginine (3 g) did not produce any change in mean blood pressure and platelet aggregation (n = 10), whereas the infusion of the L-arginine analog NG-monomethyl-L-arginine (6 mg/min) reduced by 70% the vascular effects of L-arginine. In the whole population of 52 healthy subjects, there was an inverse correlation between age and blood pressure or platelet aggregation changes after L-arginine. Compared with matched controls (n = 20), the changes in mean blood pressure and platelet aggregation after L-arginine were significantly lower in non-insulin-dependent diabetic (n = 20) and hypercholesterolemic (n = 16), but not in hypertensive (n = 20), subjects. Changes in blood viscosity were significantly lower only in hypercholesterolemic subjects. Our findings suggest that an intravenous bolus of 3 g L-arginine may be a simple and useful tool to assess the endothelial control of blood pressure and platelet activity in health and disease.

Antioxidants and atherosclerotic heart disease

Epidemiologic studies have provided evidence of an inverse relation between coronary artery disease and antioxidant intake, and vitamin E supplementation in particular. The oxidative-modification hypothesis implies that reduced atherosclerosis is a result of the production of LDL that is resistant to oxidation, but linking the reduced oxidation of LDL to a reduction in atherosclerosis has been problematic. Several important additional mechanisms may underlie the role of antioxidants in preventing the clinical manifestations of coronary artery disease (Fig. 2). Specifically, there is evidence that plaque stability, vasomotor function, and the tendency to thrombosis are subject to modification by specific antioxidants. For example, cellular antioxidants inhibit monocyte adhesion, protect against the cytotoxic effects of oxidized LDL, and inhibit platelet activation. Furthermore, cellular antioxidants protect against the endothelial dysfunction associated with atherosclerosis by preserving endothelium-derived nitric oxide activity. We speculate that these mechanisms have an important role in the benefits of antioxidants.

Effects of fluvastatin on coronary atherosclerosis in patients with mild to moderate cholesterol elevations (Lipoprotein and Coronary Atherosclerosis Study [LCAS])

Despite the potential for reduced morbidity and mortality, aggressive intervention against mild to moderate hypercholesterolemia in patients with coronary heart disease (CHD) remains controversial and infrequently practiced. Eligible patients in the 2.5-year Lipoprotein and Coronary Atherosclerosis Study were men and women aged 35 to 75 years with angiographic CHD and mean low-density lipoprotein (LDL) cholesterol of 115 to 190 mg/dl despite diet. Patients (n = 429; 19% women) were randomized to fluvastatin 20 mg twice daily or placebo. One fourth of patients were also assigned open-label adjunctive cholestyramine up to 12 g/day because prerandomization LDL cholesterol remained > or = 160 mg/dl. The primary end point, assessed by quantitative coronary angiography, was within-patient per-lesion change in minimum lumen diameter (MLD) of qualifying lesions. Across 2.5 years, mean LDL cholesterol was reduced by 23.9% in all fluvastatin patients (+/- cholestyramine) (146 to 111 mg/dl) and by 22.5% in the fluvastatin only subgroup (137 to 106 mg/dl). Primary end point analysis (340 patients) showed significantly less lesion progression in all fluvastatin versus all placebo patients, deltaMLD -0.028 versus -0.100 mm (p <0.01), and for fluvastatin alone versus placebo alone, deltaMLD -0.024 versus -0.094 mm (p <0.02). A consistent angiographic benefit with treatment was seen whether baseline LDL cholesterol was above or below 160 or 130 mg/dl. Beneficial trends with treatment were also consistently seen in clinical event rates but were not statistically significant. Thus, lipid lowering by fluvastatin in patients with mildly to moderately elevated LDL cholesterol significantly slowed CHD progression.