Effects of simvastatin on apoB metabolism and LDL subfraction distribution

Small dense low-density lipoprotein particles: clinically relevant?

PURPOSE OF REVIEW

Levels of small, dense low-density lipoprotein (LDL) (sdLDL) particles determined by several analytic procedures have been associated with risk of atherosclerotic cardiovascular disease (ASCVD). This review focuses on the clinical significance of sdLDL measurement.

RECENT FINDINGS

Results of multiple prospective studies have supported earlier evidence that higher levels of sdLDL are significantly associated with greater ASCVD risk, in many cases independent of other lipid and ASCVD risk factors as well as levels of larger LDL particles. A number of properties of sdLDL vs. larger LDL, including reduced LDL receptor affinity and prolonged plasma residence time as well as greater oxidative susceptibility and affinity for arterial proteoglycans, are consistent with their heightened atherogenic potential. Nevertheless, determination of the extent to which sdLDL can preferentially impact ASCVD risk compared with other apoprotein B-containing lipoproteins has been confounded by their metabolic interrelationships and statistical collinearity, as well as differences in analytic procedures and definitions of sdLDL.

SUMMARY

A growing body of data points to sdLDL concentration as a significant determinant of ASCVD risk. Although future studies should be aimed at determining the clinical benefit of reducing sdLDL levels, there is sufficient evidence to warrant consideration of sdLDL measurement in assessing and managing risk of cardiovascular disease.

VIDEO ABSTRACT

https://www.dropbox.com/s/lioohr2ead7yx2p/zoom_0.mp4?dl=0.

Effect of PCSK9 inhibition with evolocumab on lipoprotein subfractions in familial dysbetalipoproteinemia (type III hyperlipidemia)

BACKGROUND AND AIMS

Familial dysbetalipoproteinemia (FDBL) is a rare inborn lipid disorder characterized by the formation of abnormal triglyceride- and cholesterol-rich lipoproteins (remnant particles). Patients with FDBL have a high risk for atherosclerotic disease. The effect of PCSK9 inhibition on lipoproteins and its subfractions has not been evaluated in FDBL.

METHODS

Three patients (65±7 years, 23±3 kg/m2, 2 females) with FDBL (diagnosed by isoelectrofocusing) and atherosclerosis (coronary and/or cerebro-vascular and/or peripheral arterial disease) resistant or intolerant to statin and fibrate therapy received evolocumab (140mg every 14 days). In addition to a fasting lipid profile (preparative ultracentrifugation), apoB and cholesterol concentrations were determined in 15 lipoprotein-subfractions (density gradient ultracentrifugation; d 1.006-1.21g/ml) before and after 12 weeks of evolocumab treatment. Patients with LDL-hypercholesterolemia (n = 8, 56±8 years, 31±7 kg/m2) and mixed hyperlipidemia (n = 5, 68±12 years, 30±1 kg/m2) also receiving evolocumab for 12 weeks were used for comparison.

RESULTS

All patients tolerated PCSK9 inhibition well. PCSK9 inhibitors reduced cholesterol (29-37%), non-HDL-cholesterol (36-50%) and apoB (40-52%) in all patient groups including FDBL. In FDBL, PCSK9 inhibition reduced VLDL-cholesterol and the concentration of apoB containing lipoproteins throughout the whole density spectrum (VLDL, IDL, remnants, LDL). Lipoprotein(a) was decreased in all patient groups to a similar extent.

CONCLUSIONS

This indicates that the dominant fraction of apoB-containing lipoproteins is reduced with PCSK9 inhibition, i.e. LDL in hypercholesterolemia and mixed hyperlipidemia, and cholesterol-rich VLDL, remnants and LDL in FDBL. PCSK9 inhibition may be a treatment option in patients with FDBL resistant or intolerant to statin and/or fibrate therapy.

Triglyceride-rich lipoproteins and their remnants: metabolic insights, role in atherosclerotic cardiovascular disease, and emerging therapeutic strategies-a consensus statement from the European Atherosclerosis Society

Recent advances in human genetics, together with a large body of epidemiologic, preclinical, and clinical trial results, provide strong support for a causal association between triglycerides (TG), TG-rich lipoproteins (TRL), and TRL remnants, and increased risk of myocardial infarction, ischaemic stroke, and aortic valve stenosis. These data also indicate that TRL and their remnants may contribute significantly to residual cardiovascular risk in patients on optimized low-density lipoprotein (LDL)-lowering therapy. This statement critically appraises current understanding of the structure, function, and metabolism of TRL, and their pathophysiological role in atherosclerotic cardiovascular disease (ASCVD). Key points are (i) a working definition of normo- and hypertriglyceridaemic states and their relation to risk of ASCVD, (ii) a conceptual framework for the generation of remnants due to dysregulation of TRL production, lipolysis, and remodelling, as well as clearance of remnant lipoproteins from the circulation, (iii) the pleiotropic proatherogenic actions of TRL and remnants at the arterial wall, (iv) challenges in defining, quantitating, and assessing the atherogenic properties of remnant particles, and (v) exploration of the relative atherogenicity of TRL and remnants compared to LDL. Assessment of these issues provides a foundation for evaluating approaches to effectively reduce levels of TRL and remnants by targeting either production, lipolysis, or hepatic clearance, or a combination of these mechanisms. This consensus statement updates current understanding in an integrated manner, thereby providing a platform for new therapeutic paradigms targeting TRL and their remnants, with the aim of reducing the risk of ASCVD.

Hypocholesterolemic Effect of Pravastatin is Associated with Increased Content of Antioxidant Vitamin-E in Cholesterol Fractions

Metabolic studies support the findings that antioxidants inhibit atherosclerosis. Treatment with vitamin E reduced both the susceptibility of low density lipoprotein cholesterol (LDL-C) to in vivo lipid peroxidation and atherosclerosis and smooth muscle proliferation. Thus the aim of present study was to examine metabolic consequences of reduced plasma LDL-C during hypolipidemic therapy and the distribution of antioxidant vitamin E. A group of 10 patients (4 men, 6 women, age 35 - 65y) with familial hypercholesterolaemia was treated using pravastatin (Lipostat® Bristol Myers Squibb, 40mg daily at 6.00 PM). Blood samples were examined before treatment, after 4 and 8 weeks of therapy. After ultracentrifugation, samples were analyzed for lipoprotein fractions and the content of vitamin E and cholesterol. Pravastatin reduced both total cholesterol (9.85±0.74 vs. 6.81±0.51 mmol/l; p<0.01), LDL-C (6.42±0.45 vs. 4.51±0.45 mmol/l; p<0.01), light LDL1-C (4.56±0.50 vs. 3.11±0.34 mmol/l; p<0.05) and dense LDL2-C (1.86±0.27 vs. 1.42±0.17 mmol/l; ns). Serum vitamin E was reduced during hypolipidemic therapy in the fraction of total, LDL1, LDL2 and VLDL-cholesterol. However, the ratio of serum vitamin E/total serum cholesterol (4.57±0.32 vs. 5.12±0.37 mmol/l/mmol/l; p<0.05) and ratio of LDL2-C vitamin E/LDL2-C (3.92±0.07 vs. 4.64±0.37 mmol/l/mmol/l; p=0.08) increased in comparison to pre-treatment values. We conclude that pravastatin therapy may possess anti-atherogenic properties which involve not only its hypocholesterolemic effect, but also its favorable effects on the distribution of LDL subclasses and the content of antioxidant vitamin E in atherogenic lipoproteins.

Pharmacological Intervention to Modulate HDL: What Do We Target?

The cholesterol concentrations of low-density lipoprotein (LDL) and high-density lipoprotein (HDL) have traditionally served as risk factors for cardiovascular disease. As such, novel therapeutic interventions aiming to raise HDL cholesterol have been tested in the clinical setting. However, most trials led to a significant increase in HDL cholesterol with no improvement in cardiovascular events. The complexity of the HDL particle, which exerts multiple physiological functions and is comprised of a number of subclasses, has raised the question as to whether there should be more focus on HDL subclass and function rather than cholesterol quantity. We review current data regarding HDL subclasses and subclass-specific functionality and highlight how current lipid modifying drugs such as statins, cholesteryl ester transfer protein inhibitors, fibrates and niacin often increase cholesterol concentrations of specific HDL subclasses. In addition this review sets out arguments suggesting that the HDL3 subclass may provide better protective effects than HDL2.

Nonpharmacological approaches for reducing serum low-density lipoprotein cholesterol

PURPOSE OF REVIEW

To reinforce the key role of diet and lifestyle modification as the first-line treatment for the reduction of raised serum low-density lipoprotein cholesterol (LDL-C) and prevention of cardiovascular disease. Also, to counter recent claims that the current dietary guidelines for the treatment of cardiovascular disease have misplaced emphasis on the importance of removing dietary saturated fat instead of sugar.

RECENT FINDINGS

This review provides new insight into the effects of diet and lifestyle factors with established efficacy in lowering serum LDL-C. This includes energy-restricted weight loss and new findings on the effects of alternative day fasting; novel metabolic and molecular effects of replacing palmitic acid with oleic acid; evidence for a dose-response relationship between the intake of dietary stanols and LDL-C; and identification of a unique metabolic pathway for the excretion of cholesterol.

SUMMARY

The review reports new evidence for the efficacy of alternate day fasting, reassurance that the current dietary guidelines are not misguided by recommending removal of saturated fat, that a high intake of dietary stanols can achieve a reduction in LDL-C of up to 18%, and describes a pathway of cholesterol excretion that may help to explain variation in the response of serum LDL-C to dietary fat and cholesterol.

Effects of fluvastatin on plasma levels of low-density lipoprotein subfractions, oxidized low-density lipoprotein, and soluble adhesion molecules: a twenty-four-week, open-label, dose-increasing study

BACKGROUND

Statins not only lower low-density lipoprotein (LDL) levels, but also have several antiarteriosclerotic effects (eg, decreasing arterial inflammation and arterial smooth muscle cell proliferation, as well as antioxidant effects). The relationship between the dose of statin and its effects on plasma LDL levels and other arteriosclerosis-related effects remains to be clarified.

OBJECTIVE

We investigated the effect of a statin, fluvastatin, on plasma levels of lipoprotein subfractions, oxidized LDL (Ox-LDL), Ox-LDL immunoglobulin G (IgG), soluble adhesion molecules, reverse cholesterol transport (ie, transport of esterified high-density lipoprotein cholesterol [HDL-C] to triglyceride [TG]-rich lipoproteins by cholesteryl ester transfer protein [CETP] and reduction of plasma HDL-C levels), and on the intima-medial thickness (IMT) of the common carotid arteries.

METHODS

Patients with nonfamilial type 2 hyperlipoproteinemia were eligible for this open-label, dose-increasing study. Fluvastatin 20 mg/d was administered for the first 12 weeks, and the daily dose was increased to 40 mg for the subsequent 12 weeks. Patients were examined at baseline and after 12 and 24 weeks of treatment. Plasma lipoprotein subfractions were determined using sequential ultracentrifugation at 100,000g. The plasma levels of Ox-LDL, Ox-LDL-IgG, CETP, and soluble adhesion molecules were measured using sandwich enzyme-linked immunosorbent assay. The maximum IMT of the common carotid arteries was measured using sonography.

RESULTS

The plasma levels of LDL cholesterol (LDL-C) and apolipoprotein (apo) B were reduced by 25% and 17%, respectively (P<0.001 for both), after 12 weeks of treatment with fluvastatin 20 mg/d; no further significant reductions in LDL were observed after increasing the daily dose to 40 mg. Fluvastatin 20 mg/d for 12 weeks decreased plasma levels of intermediate-density lipoprotein cholesterol, LDL-I-C, LDL-II-C, and LDL-III-C by 25% (P<0.01), 30% (P<0.001), 23% (P<0.01), and 20% (P = 0.02), respectively. No further significant reductions in these levels were observed after increasing the daily dose to 40 mg. The plasma levels of Ox-LDL decreased in a similar fashion to the plasma levels of LDL-C (P<0.001). However, plasma levels of Ox-LDL-IgG and soluble P-selectin did not decrease after 12 weeks of fluvastatin 20 mg/d, but did decrease significantly (both 22%) after the next 12 weeks of treatment with fluvastatin 40 mg/d (P<0.05). Plasma levels of intercellular adhesion molecule 1and vascular cell adhesion molecule 1 and CETP mass were not altered by fluvastatin treatment. Significant changes in maximum IMT of the common carotid arteries were not seen throughout 24 weeks of fluvastatin treatment.

CONCLUSIONS

In this patient population, fluvastatin 20 mg/d was sufficient to significantly reduce plasma levels of LDL, the 3 LDL subfractions, and Ox-LDL, but was not sufficient to reduce plasma levels of Ox-LDL-IgG and soluble P-selectin. It is important to check not only plasma lipoprotein levels but also other factors relating to arteriosclerosis during treatment with statins for the prevention and treatment of arteriosclerosis.

Hypolipidemic treatment of heterozygous familial hypercholesterolemia: a lifelong challenge

In familial hypercholesterolemia, a defect in low-density lipoprotein receptors causes lifelong two- to threefold elevations in serum low-density lipoprotein-cholesterol levels. This leads to early atherosclerotic changes in infancy. Lifelong hypolipidemic treatment that can be started at a young age is thus greatly needed. Early diagnosis of familial hypercholesterolemia is important, and improved DNA tests for low-density lipoprotein receptor mutations have made it possible to carry out diagnosis at birth. A low saturated-fat, low cholesterol diet can be safely started at 7 months of age. This can be accompanied by dietary stanol esters from 2 years of age. At the age of 10, statin treatment can be safely started. In adults, more aggressive hypolipidemic treatment is required in order to reach the treatment goal for serum low-density lipoprotein-cholesterol levels less than 2.5 mmol/l. This can be achieved by using high doses of statin, or preferably by combining a statin with resin or ezetimibe (Zeita), Merck and Shering-Plough Pharmaceuticals). Once started, treatment of familial hypercholesterolemia is lifelong.

[Pathogenetic justification of statin use in ischaemic stroke prevention according to inflammatory theory in development of atherosclerosis]

There is an inflammatory component in the pathogenesis of ischaemic stroke, which plays an important role in inducing atherothrombotic and embolic stroke. Statins, HMG-CoA (3-hydroxy-3-methyl-glutaryl-coenzyme A) reductase inhibitors are widely used in the primary and secondary prevention of ischaemic stroke. It has been proved that beyond their main effect on inhibition of endogenous cholesterol, they also modify the inflammatory process. Additional benefits from the use of statins result from their effect on the immune system. Increased risk of recurrent vascular episodes and risk of death after statin withdrawal in patients with vascular disorders is connected with termination of the anti-inflammatory effect of these drugs. The authors highlight that because of the anti-inflammatory effect of statins it is reasonable to use them in all patients at risk of ischaemic stroke, including those with atrial fibrillation.

Opening a new lipid "apo-thecary": incorporating apolipoproteins as potential risk factors and treatment targets to reduce cardiovascular risk

Statins (3-hydroxy-3-methylglutaryl-coenzyme A reductase inhibitors) represent the cornerstone of drug therapy to reduce low-density lipoprotein (LDL) cholesterol and cardiovascular risk. However, even optimal statin management of LDL cholesterol leaves many patients with residual cardiovascular risk, in part because statins are more effective in reducing LDL cholesterol than apolipoprotein B (Apo B). Apo B may be a better marker of atherogenic risk than LDL cholesterol because Apo B measures the total number of all atherogenic particles (total atherosclerotic burden), including LDL, very low-density lipoprotein, intermediate-density lipoprotein, remnant lipoproteins, and lipoprotein(a). To determine whether Apo B is a better indicator of baseline cardiovascular risk and residual risk after lipid therapy compared with LDL cholesterol, a MEDLINE search of the literature published in English from January 1, 1975, through December 1, 2010, was conducted. On the basis of data from most population studies, elevated Apo B was more strongly associated with incident coronary heart disease than similarly elevated LDL cholesterol. Apo B was also a superior benchmark (vs LDL cholesterol) of statins' cardioprotective efficacy in both primary-prevention and secondary-prevention trials. To minimize cardiovascular risk among persons with hypercholesterolemia or dyslipidemia, the best available evidence suggests that intensive therapy with statins should be initiated to achieve the lowest possible Apo B level (with adequate drug toleration) and then other therapies (eg, niacin, bile acid resins, ezetimibe) added to potentiate these Apo B-lowering effects. In future consensus lipid-lowering treatment guidelines, Apo B should be considered as an index of residual risk, a potential parameter of treatment efficacy, and a treatment target to minimize risk of coronary heart disease.

The effect of simvastatin alone versus simvastatin plus ezetimibe on the concentration of small dense low-density lipoprotein cholesterol in subjects with primary hypercholesterolemia

OBJECTIVE

To compare the effects of simvastatin alone versus simvastatin plus ezetimibe on small dense low-density lipoprotein cholesterol (sdLDL-C) concentration in subjects with primary hypercholesterolemia.

RESEARCH DESIGN AND METHODS

Patients with LDL-C levels above those recommended by the National Cholesterol Education Program Adult Treatment Panel III were randomized to open-label simvastatin 40 mg (n = 50) or simvastatin/ezetimibe 10/10 mg as a fixed combination (n = 50) daily. LDL particle size (estimated by electrophoresis), sdLDL-C levels, and lipid profile were blindly assessed at baseline and 3 months.

CLINICAL TRIAL REGISTRATION

clinicaltrials.gov NCT00932620.

RESULTS

Both simvastatin 40 mg and simvastatin/ezetimibe 10/10 mg decreased total cholesterol (-31% and -36%, respectively), LDL-C (-43% and -49%, respectively), triglycerides (-17% and -19%, respectively), non-high-density lipoprotein cholesterol (non-HDL-C; -40% and -46%, respectively), large LDL-C (-40 and -44%, respectively) and sdLDL-C levels (-42% and -46%, respectively, all p < 0.000 vs baseline) and increased LDL particle size (+0.5% and +0.7%, respectively, both p < 0.05 vs baseline). The changes in total cholesterol, LDL-C and non-HDL-C were greater in the simvastatin/ezetimibe group (all p < 0.05). Changes in triglycerides, large LDL-C, sdLDL-C levels and LDL particle size were similar in the two groups. In multivariate analysis, baseline sdLDL-C and triglyceride levels, but not the choice of treatment, were significantly and independently correlated with the changes in sdLDL-C levels.

CONCLUSION

The combination of simvastatin 10 mg plus ezetimibe 10 mg is similarly effective to simvastatin 40 mg in improving sdLDL-C concentration and LDL particle size in subjects with primary hypercholesterolemia.

Dyslipidaemia in the metabolic syndrome and type 2 diabetes: pathogenesis, priorities, pharmacotherapies

IMPORTANCE OF THE FIELD

Dyslipoproteinaemia is a cardinal feature of the metabolic syndrome that accelerates atherosclerosis. It is usually characterized by high plasma concentrations of triglyceride-rich and apolipoprotein B (apoB)-containing lipoproteins, with depressed concentrations of high-density lipoprotein (HDL). Drug interventions are essential for normalizing metabolic dyslipidaemia.

AREAS COVERED IN THIS REVIEW

This review discusses the mechanisms and treatment for dyslipidaemia in the metabolic syndrome and type 2 diabetes.

WHAT THE READER WILL GAIN

A comprehensive understanding of the pathophysiology and pharmacotherapy of dyslipidaemia in the metabolic syndrome and diabetes.

TAKE HOME MESSAGE

Dysregulation of lipoprotein metabolism may be due to a combination of overproduction of triglyceride-rich lipoproteins, decreased catabolism of apoB-containing particles, and increased catabolism of HDL particles. These abnormalities may be consequent on a global metabolic effect of insulin resistance and an excess of both visceral and hepatic fat. Lifestyle modifications may favourably alter lipoprotein transport in the metabolic syndrome. Patients with dyslipidaemia and established cardiovascular disease should receive a statin as first-line therapy. Combination with other lipid-regulating agents, such as ezetimibe, fibrates, niacins and fish oils may optimize the benefit of statin on atherogenic dyslipidaemia.

Influence of simvastatin on apoB-100 secretion in non-obese subjects with mild hypercholesterolemia

Statins decrease apoB-100-containing lipoproteins by increasing their fractional catabolic rates through LDL receptor-mediated uptake. Their influence on hepatic secretion of these lipoproteins is controversial. The objective of the study was to examine the influence of simvastatin on the secretion of apoB-100-containing lipoproteins in fasting non-obese subjects. Turnover of apoB-100-containing lipoproteins was investigated using stable isotope-labeled tracers. Multicompartmental modeling was used to derive kinetic parameters. Eight male subjects (BMI 25 +/- 3 kg/m(2)) with mild hypercholesterolemia (LDL cholesterol 135 +/- 30 mg/dL) and normal triglycerides (111 +/- 44 mg/dL) were examined under no treatment (A), under chronic treatment with simvastatin 40 mg/day (B) and after an acute-on-chronic dosage of 80 mg simvastatin under chronic simvastatin treatment (C). Lipoprotein concentrations changed as expected under 40 mg/day simvastatin. Fractional catabolic rates increased in IDL and LDL but not in VLDL fractions versus control [VLDL +35% in B (n.s.) and +21% in C (n.s.); IDL +169% in B (P = 0.08) and +187% in C (P = 0.032); LDL +87% in B (P = 0.025) and +133% in C (P = 0.025)]. Chronic (B) and acute-on-chronic simvastatin treatment (C) did not affect lipoprotein production rates [VLDL -8 and -13%, IDL +47 and +38%, and LDL +19 and +30% in B and C, respectively (all comparisons n.s.)]. The data indicate that simvastatin does not influence the secretion of apoB-100-containing lipoproteins in non-obese subjects with near-normal LDL cholesterol concentrations.

Effect of L-carnitine on the size of low-density lipoprotein particles in type 2 diabetes mellitus patients treated with simvastatin

Therapeutic modulation of low-density lipoprotein (LDL) size could be of benefit in reducing the risk of cardiovascular events in diabetic patients. This study evaluated the efficacy of L-carnitine on the size of LDL particles in type 2 diabetes mellitus patients treated with simvastatin. Eighty diabetic patients were randomly assigned to 1 of 2 treatment groups for 3 months. The 2 groups received either simvastatin monotherapy 20 mg (n = 40) or L-carnitine 2 g/d and simvastatin 20 mg (n = 40). The following variables were assessed at baseline; after washout; and at 1, 2, and 3 months of treatment: body mass index, fasting plasma glucose, glycosylated hemoglobin, total cholesterol, LDL cholesterol, LDL subclasses, LDL size, high-density lipoprotein cholesterol, triglycerides, apolipoprotein A-1, and apolipoprotein B-100. After 12 weeks, comparing the 2 groups, we observed a decrease in fasting plasma glucose (1.45 vs 0.61 mmol/L, P < .001) and an increase in glycosylated hemoglobin (0.2% vs 0.4%, P < .05). Moreover, there was a decrease in total cholesterol (2.07 vs 1.45 mmol/L, P < .001), LDL (1.65 vs 1.29 mmol/L, P < .001), triglycerides (1.36 vs 0.41 mmol/L, P < .001), apo B-100 (49 vs 9 g/L, P < .001), and small-sized LDL proportion (10.8% vs 4.9%, P < .001), whereas LDL particle size increased (6 vs 3 A, P < .001) and HDL increased (0.2 vs 0.11 mmol/L, P < .001). We observed that patients treated with carnitine and simvastatin showed a reduction in small-sized LDL proportion and an increase in LDL particle size.

Targets of statin therapy: LDL cholesterol, non-HDL cholesterol, and apolipoprotein B in type 2 diabetes in the Collaborative Atorvastatin Diabetes Study (CARDS)

BACKGROUND

LDL can vary considerably in its cholesterol content; thus, lowering LDL cholesterol (LDLC) as a goal of statin treatment implies the existence of considerable variation in the extent to which statin treatment removes circulating LDL particles. This consideration is particularly applicable in diabetes mellitus, in which LDL is frequently depleted of cholesterol.

METHODS

Type 2 diabetes patients randomly allocated to 10 mg/day atorvastatin (n = 1154) or to placebo (n = 1196) for 1 year were studied to compare spontaneous and statin-induced apolipoprotein B (apo B) concentrations (a measure of LDL particle concentration) at LDLC and non-HDL cholesterol (non-HDLC) concentrations proposed as statin targets in type 2 diabetes.

RESULTS

Patients treated with atorvastatin produced lower serum apo B concentrations at any given LDLC concentration than patients on placebo. An LDLC concentration of 1.8 mmol/L (70 mg/dL) during atorvastatin treatment was equivalent to a non-HDLC concentration of 2.59 mmol/L (100 mg/dL) or an apo B concentration of 0.8 g/L. At the more conservative LDLC targets of 2.59 mmol/L (100 mg/dL) and 3.37 mmol/L (130 mg/dL) for non-HDLC, however, the apo B concentration exceeded the 0.9-g/L value anticipated in the recent Consensus Statement from the American Diabetes Association and the American College of Cardiology.

CONCLUSIONS

The apo B concentration provides a more consistent goal for statin treatment than the LDLC or non-HDLC concentration.

Comparison of atorvastatin versus fenofibrate in reaching lipid targets and influencing biomarkers of endothelial damage in patients with familial combined hyperlipidemia

Statins and fibrates have different effects on lipid abnormalities of familial combined hyperlipidemia (FCHL); thus, the selection of the first-line drug is troublesome. We evaluated to what extent monotherapy with a potent statin is more effective than fibrate in reaching the recommended lipid targets in FCHL. Fifty-six patients were randomized to receive optimal dosage of atorvastatin (n = 27) or 200 mg/d micronized fenofibrate (n = 29) for 24 weeks. To reach the optimal dosage, atorvastatin was up-titrated at each follow-up visit if low-density lipoprotein (LDL) cholesterol >130 mg/dL (>100 mg/dL in patients with coronary or cerebrovascular disease). The effects of fenofibrate and atorvastatin on lipoprotein fractions as well as on plasma levels of endothelin-1 (ET-1) and adrenomedullin (AM) were also evaluated. At end of trial, a greater proportion of patients on atorvastatin (average dosage, 20.8 mg/d) reached lipid targets in comparison with those on fenofibrate (64% vs 32.1%, P = .02). Atorvastatin was significantly more effective in reducing total cholesterol, LDL cholesterol, apolipoprotein B, and non-high-density lipoprotein (HDL) cholesterol. Conversely, triglycerides decreased and HDL increased more during fenofibrate. Nevertheless, atorvastatin produced a marked reduction in very low-density lipoprotein and very low-density lipoprotein remnants. Atorvastatin lowered all LDL subtypes, although fenofibrate appeared to be more effective on denser LDL. Compared with 43 normolipemic controls, FCHL patients presented increased baseline plasma levels of ET-1 (P = .007) but not of AM. Fenofibrate, but not atorvastatin, significantly lowered ET-1 levels by 16.7% (P < .05). Neither drug significantly affected plasma concentrations of AM. In summary, although fenofibrate showed superiority in raising HDL and reducing ET-1, atorvastatin was more effective in reaching lipid targets in FCHL so that it can be proposed as the first-line option in the management of this atherogenic hyperlipidemia.

Clinical importance and therapeutic modulation of small dense low-density lipoprotein particles

The National Cholesterol Education Programme Adult Treatment Panel III accepted the predominance of small dense low-density lipoprotein (sdLDL) as an emerging cardiovascular disease (CVD) risk factor. Most studies suggest that measuring low-density lipoprotein (LDL) particle size, sdLDL cholesterol content and LDL particle number provides additional assessment of CVD risk. Therapeutic modulation of small LDL size, number and distribution may decrease CVD risk; however, no definitive causal relationship is established, probably due to the close association between sdLDL and triglycerides and other risk factors (e.g., high-density lipoprotein, insulin resistance and diabetes). This review addresses the formation and measurement of sdLDL, as well as the relationship between sdLDL particles and CVD. The effect of hypolipidaemic (statins, fibrates and ezetimibe) and hypoglycaemic (glitazones) agents on LDL size and distribution is also discussed.

The Clinical Relevance of Low-Density-Lipoproteins Size Modulation by Statins

The predominance of small, dense low density lipoproteins (LDL) has been accepted as an emerging cardiovascular risk factor by the National Cholesterol Education Program Adult Treatment Panel III; in fact, LDL size seems to be an important predictor of cardiovascular events and progression of coronary heart disease. Several studies have also shown that the therapeutical modulation of LDL size is of great benefit in reducing the risk of cardiovascular events. Hypolipidemic treatment is able to alter LDL subclass distribution and statins are currently the most widely used lipid-lowering agents. Statins are potent inhibitors of hydroxy-methyl-glutaryl-coenzyme A reductase, the rate-limiting enzyme in hepatic cholesterol synthesis and are the main drugs of choice for the treatment of elevated plasma LDL cholesterol concentrations. Statins potentially lower all LDL subclasses (e.g., large, medium and small particles); thus, their net effect on LDL subclasses or size is often only moderate. However, a strong variation has been noticed among the different agents: analyses of all published studies suggest a very limited role of pravastatin and simvastatin in modifying LDL size and their subclasses, while fluvastatin and atorvastatin seem to be much more effective agents. Finally, rosuvastatin, the latest statin molecule introduced in the market, seems to be promising in altering LDL subclasses towards less atherogenic particles.

Apolipoproteins AI and B as therapeutic targets

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

Low-density lipoprotein size and cardiovascular risk assessment

A predominance of small, dense low-density lipoproteins (LDL) has been accepted as an emerging cardiovascular risk factor by the National Cholesterol Education Program Adult Treatment Panel III. LDL size seems to be an important predictor of cardiovascular events and progression of coronary heart disease and evidences suggests that both quality (particularly small, dense LDL) and quantity may increase cardiovascular risk. However, other authors have suggested that LDL size measurement does not add information beyond that obtained by measuring LDL concentration, triglyceride levels and HDL concentrations. Therefore, it remains debatable whether to measure LDL particle size in cardiovascular risk assessment and, if so, in which categories of patient. Therapeutic modulation of LDL particle size or number appears beneficial in reducing the risk of cardiovascular events, but no clear causal relationship has been shown, because of confounding factors, including lipid and non-lipid variables. Studies are needed to investigate the clinical significance of LDL size measurements in patients with coronary and non-coronary forms of atherosclerosis; in particular, to test whether LDL size is associated with even higher vascular risk, and whether LDL size modification may contribute to secondary prevention in such patients.

Beneficial effects of atorvastatin on sd LDL and LDL phenotype B in statin-naive patients and patients previously treated with simvastatin or pravastatin

BACKGROUND

The presence of increased levels of small dense (sd) LDL (phenotype B) is associated with a substantial increase of cardiovascular disease risk. Since lowering of plasma low-density lipoprotein-cholesterol (LDL-C) by statins involves an up-regulation of the LDL receptor, we questioned whether LDL lowering by atorvastatin affects different LDL subfractions equally.

METHODS

Fifty-four hypercholesterolemic patients, requiring treatment for prevention of coronary heart disease received atorvastatin (10, 20 or 40 mg/day), either as initial therapy (n=33), or as replacement therapy (n=21) for pravastatin or simvastatin (both at 40 mg/day). In addition to plasma lipid measurements, cholesterol LDL subfractions were separated and analysed before and after 3 months of treatment.

RESULTS

In addition to the expected LDL-C decrease (-34%; p<0.0001), a major reduction in sd LDL occurred after atorvastatin therapy (-38.2%; p<0.0001). Interestingly, sd LDL decreased as much in patients previously treated with other statins (-36%; p<0.002). A close correlation (r=0.89, p<0.001) was found between reduction of sd LDL and that of LDL-C, in patients with phenotype B. Although high-density lipoprotein-cholesterol (HDL-C) was not affected by atorvastatin treatment, plasma triglycerides decreased by 27.4% (p<0.0001). Only a weak correlation (r=0.35, p<0.01) was found between the reduction of plasma triglycerides and the decrease of sd LDL after atorvastatin treatment.

CONCLUSION

These results show that the reduction of LDL-C by atorvastatin largely reflects a lowering of sd LDL. Our data also suggest that triglyceride lowering plays only a partial role in sd LDL reduction.

Lipids in health and disease

The evidence linking cholesterol levels in the blood to vascular risk is now incontrovertible and the introduction of HMG CoA (3-hydroxy-3-methylglutaryl coenzyme A) reductase inhibitor (or statin) therapy into clinical practice has now revolutionized the management of lipid disorders and silenced at a stroke the critics of cholesterol control as a means to vascular disease prevention. Statins were the first lipid-lowering agents, which, within a framework of a clinical trial, actually extended life by mechanisms that probably go beyond cholesterol alone. Their benefits are so impressive that some enthusiasts have been emboldened to write that they 'are to atherosclerosis what penicillin was to infectious disease'. But is Nature as easily tamed as we might imagine? Some individuals show a modest or even poor response to statin therapy. The recent discovery of ezetimibe, a highly efficient and precise cholesterol absorption inhibitor, has proven to be a very effective cholesterol lowering alternative for them and combining statins with ezetimibe, thereby inhibiting cholesterol absorption and endogenous synthesis, takes us to realms of cholesterol lowering capability that could not have been dreamt of a decade ago.

Effects of increasing doses of simvastatin on fasting lipoprotein subfractions, and the effect of high-dose simvastatin on postprandial chylomicron remnant clearance in normotriglyceridemic patients with premature coronary sclerosis

Postprandial hyperlipidemia has been linked to premature coronary artery disease (CAD) in fasting normotriglyceridemic patients. We investigated the effects of increasing doses of simvastatin up to 80 mg/day on fasting and postprandial lipoprotein metabolism in 18 normotriglyceridemic patients with premature CAD. Fasting lipoprotein subfractions and cholesteryl ester transfer protein (CETP) activity were determined after each 5-week dose titration (0, 20, 40 and 80 mg/day). At baseline and after treatment with simvastatin 80 mg/day, standardised Vitamin A oral fat loading tests (50 g/m2; 10 h) were carried out. Ten normolipidemic healthy control subjects matched for gender, age and BMI underwent tests without medication. Treatment with simvastatin resulted in dose-dependent reductions of fasting LDL-cholesterol, without changing cholesterol levels in the VLDL-1, VLDL-2 and IDL fractions. In addition, simvastatin decreased CETP activity dose-dependently, although HDL-cholesterol remained unchanged. Simvastatin 80 mg/day decreased fasting plasma triglycerides (TG) by 26% (P < 0.05), but did not decrease significantly TG levels in any of the subfractions. The TG/cholesterol ratio increased in all subfractions. The plasma TG response to the oral fat loading test, estimated as area under the curve (TG-AUC), improved by 30% (from 21.5 +/- 2.5 to 15.1 +/- 1.9 mmol h/L; P < 0.01). Treatment with simvastatin 80 mg/day improved chylomicron remnant clearance (RE-AUC) by 36% from 30.0 +/- 2.6 to 19.2 +/- 3.3 mg h/L (P < 0.01). After therapy, remnant clearance in patients was similar to controls (19.2 +/- 3.3 and 20.3 +/- 2.7 mg h/L, respectively), suggesting a normalization of this potentially atherogenic process. In conclusion, high-dose simvastatin has beneficial effects in normotriglyceridemic patients with premature CAD, due to improved chylomicron remnant clearance, besides effective lowering of LDL-cholesterol. In addition, the lipoprotein subfractions became more cholesterol-poor, as reflected by the increased TG/cholesterol ratio, which potentially makes them less atherogenic.

In vivo metabolism of LDL subfractions in patients with heterozygous FH on statin therapy

LDL can be subfractionated into buoyant (1.020-1.029 g/ml(-1)), intermediate (1.030-1.040 g/ml(-1)), and dense (1.041-1.066 g/ml(-1)) LDLs. We studied the rebound of these LDL-subfractions after LDL apheresis in seven patients with heterozygous familial hypercholesterolemia (FH) regularly treated by apheresis (58 +/- 9 years, LDL-cholesterol = 342 +/- 87 mg/dl(-1), triglycerides = 109 +/- 39 mg/dl(-1)) and high-dose statins. Apolipoprotein B (apoB) concentrations were measured in LDL subfractions immediately after and on days 1, 2, 3, 5, and 7 after apheresis. Compartmental models were developed to test three hypotheses: 1) that dense LDLs are derived from the delipidation of buoyant and intermediate LDLs (model A); 2) that dense LDLs are generated directly from LDL-precursors (model B); or 3) that a model combining both pathways (model C) is necessary to describe the metabolism of dense LDLs. In all models, it was assumed that apoB production and fractional catabolic rate (FCR) did not change with apheresis. Apheresis decreased buoyant, intermediate, and dense LDL-apoB by 60 +/- 12%, 67 +/- 5%, and 69 +/- 11%, respectively. Models B and C, but not model A, described the rebound data. The model with the greatest biological plausibility (model C) was used to estimate metabolic parameters. FCR was 1.05 +/- 0.86 d(-1), 0.48 +/- 0.11 d(-1), and 0.69 +/- 0.24 d(-1) for buoyant, intermediate, and dense LDLs, respectively. Dense LDL production was 17.3 +/- 0.2 mg/kg(-1)/d(-1), 58% of which was derived directly from LDL precursors (VLDL, IDL, or direct secretion), while 42% was derived from buoyant and intermediate LDLs. Thus, our data indicate that in statin-treated patients with heterozygous FH dense LDLs originate from two sources. Whether this is also valid in other metabolic situations (with predominant small, dense LDLs) remains to be determined.

Phenotype-dependent and -independent actions of rosuvastatin on atherogenic lipoprotein subfractions in hyperlipidaemia

This randomised, double-blind, placebo-controlled crossover study evaluated the effects of rosuvastatin (40 mg/day for 8 weeks) on atherogenic apolipoprotein B-containing lipoprotein subfractions. Subjects, recruited based on raised plasma triglyceride (TG) or low-density lipoprotein cholesterol (LDL-C), were divided into normotriglyceridaemic (NTG, n = 13; TG < 2.0 mmol/l) and hypertriglyceridaemic (HTG, n = 16; TG > or = 2.0 mmol/l) groups. Similar reductions on rosuvastatin were observed for both groups in LDL-C (NTG -60%; HTG -56%), apoB (both -49%), intermediate-density lipoprotein (NTG -57%; HTG -54%) and LDL circulating mass (NTG -52%, HTG -58%) (all P < 0.001 versus placebo), i.e., these changes were phenotype independent. Phenotype dependency in response was observed in HTG relative to NTG in concentration of small dense LDL (LDL-III) (NTG -44%, P = NS; HTG -69%, P < 0.001), very-low-density lipoprotein1 (NTG -18%, P = NS; HTG 46%, P < 0.01), and remnant-like particle cholesterol (NTG -31%, P = NS; HTG -48%, P < 0.05). Rosuvastatin reduced cholesteryl ester transfer protein (CETP) by 33% in NTG and 37% in HTG (both P < 0.001); a reduction in cholesteryl ester transfer activity (-59%, P < 0.001) was observed in HTG only. Rosuvastatin therefore, in addition to lowering LDL and apoB-concentrations, largely corrected the TG and LDL abnormalities in subjects who had the propensity to develop the atherogenic lipoprotein phenotype.

Effects of atorvastatin on electrophoretic characteristics of LDL particles among subjects with heterozygous familial hypercholesterolemia

The effects of the HMG CoA reductase inhibitor atorvastatin on electrophoretic characteristics of LDL particles were evaluated in 46 patients (28 males and 18 females) with heterozygous familial hypercholesterolemia (FH) aged 20-61 carrying either a negative or a defective LDL receptor gene mutation. Following a 6 week drug-free baseline period, FH heterozygotes were treated with atorvastatin (median dose: 20 mg/day, range 10-80 mg/day)) for 6 months to maintain their plasma LDL-cholesterol concentrations between 4.0 and 5.0 mmol/l. Atorvastatin treatment significantly reduced plasma total cholesterol, LDL-cholesterol and triglyceride levels and increased plasma HDL-cholesterol. Furthermore, atorvastatin treatment significantly increased LDL peak particle diameter (LDL-PPD) by 0.5% (from 255.0+/-6.2 to 256.4+/-5.5 A, P=0.004) and reduced the absolute concentration of cholesterol among small (<255 A) and large (>260 A) LDL particles by 35% (P<0.001). Changes in LDL-PPD and plasma triglyceride levels were inversely correlated (R=-0.34; P=0.02). Stepwise multiple linear regression analyses showed that 41.6% of the variation in the LDL-PPD response to atorvastatin was attributable to the initial LDL-PPD (14.4%, P=0.003), the apo E polymorphism (12.4%, P=0.02), the nature of the LDL receptor gene mutation (9.6%, P=0.01) and change in triglyceride levels (5.2%, P=0.04). Moreover, the reduction in the cholesterol content of LDL <255 A was directly correlated with the daily dosage of atorvastatin (P=0.05). Results of the present study showed that atorvastatin alters significantly LDL heterogeneity in patients at high risk of coronary heart disease (CHD) such as FH heterozygotes. These results also suggest that genetic and metabolic factors may be important determinants of atorvastatin-induced changes of LDL particle size and distribution among FH heterozygotes.

Differential regulation of lipoprotein kinetics by atorvastatin and fenofibrate in subjects with the metabolic syndrome

The metabolic syndrome is characterized by insulin resistance and abnormal apolipoprotein AI (apoAI) and apolipoprotein B-100 (apoB) metabolism that may collectively accelerate atherosclerosis. The effects of atorvastatin (40 mg/day) and micronised fenofibrate (200 mg/day) on the kinetics of apoAI and apoB were investigated in a controlled cross-over trial of 11 dyslipidemic men with the metabolic syndrome. ApoAI and apoB kinetics were studied following intravenous d(3)-leucine administration using gas-chromatography mass spectrometry with data analyzed by compartmental modeling. Compared with placebo, atorvastatin significantly decreased (P < 0.001) plasma concentrations of cholesterol, triglyceride, LDL cholesterol, VLDL apoB, intermediate-density lipoprotein (IDL) apoB, and LDL apoB. Fenofibrate significantly decreased (P < 0.001) plasma triglyceride and VLDL apoB and elevated HDL(2) cholesterol (P < 0.001), HDL(3) cholesterol (P < 0.01), apoAI (P = 0.01), and apoAII (P < 0.001) concentrations, but it did not significantly alter LDL cholesterol. Atorvastatin significantly increased (P < 0.002) the fractional catabolic rate (FCR) of VLDL apoB, IDL apoB, and LDL apoB but did not affect the production of apoB in any lipoprotein fraction or in the turnover of apoAI. Fenofibrate significantly increased (P < 0.01) the FCR of VLDL, IDL, and LDL apoB but did not affect the production of VLDL apoB. Relative to placebo and atorvastatin, fenofibrate significantly increased the production (P < 0.001) and FCR (P = 0.016) of apoAI. Both agents significantly lowered plasma triglycerides and apoCIII concentrations, but only atorvastatin significantly lowered (P < 0.001) plasma cholesteryl ester transfer protein activity. Neither treatment altered insulin resistance. In conclusion, these differential effects of atorvastatin and fenofibrate on apoAI and apoB kinetics support the use of combination therapy for optimally regulating dyslipoproteinemia in the metabolic syndrome.

Effect of weight loss on VLDL-triglyceride and apoB-100 kinetics in women with abdominal obesity

The effects of obesity and weight loss on lipoprotein kinetics were evaluated in six lean women [body mass index (BMI): 21 +/- 1 kg/m(2)] and seven women with abdominal obesity (BMI: 36 +/- 1 kg/m(2)). Stable isotope tracer techniques, in conjunction with compartmental modeling, were used to determine VLDL-triglyceride (TG) and apolipoprotein B-100 (apoB-100) secretion rates in lean women and in obese women before and after 10% weight loss. VLDL-TG and VLDL-apoB-100 secretion rates were similar in lean and obese women. Weight loss decreased the rate of VLDL-TG secretion by approximately 40% (from 0.41 +/- 0.05 to 0.23 +/- 0.03 micromol x kg fat-free mass(-1) x min(-1); P < 0.05). The relative decline in VLDL-TG produced from nonsystemic fatty acids, derived from intraperitoneal and intrahepatic TG, was greater (61 +/- 7%) than the decline in VLDL-TG produced from systemic fatty acids, predominantly derived from subcutaneous TG (25 +/- 8%; P < 0.05). Weight loss did not affect VLDL-apoB-100 secretion rate. We conclude that weight loss decreases the rate of VLDL-TG secretion in women with abdominal obesity, primarily by decreasing the availability of nonsystemic fatty acids. There is a dissociation in the effect of weight loss on VLDL-TG and apoB-100 metabolic pathways that may affect VLDL particle size.

Influence of atorvastatin and simvastatin on apolipoprotein B metabolism in moderate combined hyperlipidemic subjects with low VLDL and LDL fractional clearance rates

Subjects with moderate combined hyperlipidemia (n=11) were assessed in an investigation of the effects of atorvastatin and simvastatin (both 40 mg per day) on apolipoprotein B (apoB) metabolism. The objective of the study was to examine the mechanism by which statins lower plasma triglyceride levels. Patients were studied on three occasions, in the basal state, after 8 weeks on atorvastatin or simvastatin and then again on the alternate treatment. Atorvastatin produced significantly greater reductions than simvastatin in low density lipoprotein (LDL) cholesterol (49.7 vs. 44.1% decrease on simvastatin) and plasma triglyceride (46.4 vs. 39.4% decrease on simvastatin). ApoB metabolism was followed using a tracer of deuterated leucine. Both drugs stimulated direct catabolism of large very low density lipoprotein (VLDL(1)) apoB (4.52+/-3.06 pools per day on atorvastatin; 5.48+/-4.76 pools per day on simvastatin versus 2.26+/-1.65 pools per day at baseline (both P<0.05)) and this was the basis of the 50% reduction in plasma VLDL(1) concentration; apoB production in this fraction was not significantly altered. On atorvastatin and simvastatin the fractional transfer rates (FTR) of VLDL(1) to VLDL(2) and of VLDL(2) to intermediate density lipoprotein (IDL) were increased significantly, in the latter instance nearly twofold. IDL apoB direct catabolism rose from 0.54+/-0.30 pools per day at baseline to 1.17+/-0.87 pools per day on atorvastatin and to 0.95+/-0.43 pools per day on simvastatin (both P<0.05). Similarly the fractional transfer rate for IDL to LDL conversion was enhanced 58-84% by statin treatment (P<0.01) LDL apoB fractional catabolic rate (FCR) which was low at baseline in these subjects (0.22+/-0.04 pools per day) increased to 0.44+/-0.11 pools per day on atorvastatin and 0.38+/-0.11 pools per day on simvastatin (both P<0.01). ApoB-containing lipoproteins were more triglyceride-rich and contained less free cholesterol and cholesteryl ester on statin therapy. Further, patients on both treatments showed marked decreases in all LDL subfractions. In particular the concentration of small dense LDL (LDL-III) fell 64% on atorvastatin and 45% on simvastatin. We conclude that in patients with moderate combined hyperlipidemia who initially have a low FCR for VLDL and LDL apoB, the principal action of atorvastatin and simvastatin is to stimulate receptor-mediated catabolism across the spectrum of apoB-containing lipoproteins. This leads to a substantial, and approximately equivalent, percentage reduction in plasma triglyceride and LDL cholesterol.

Metabolic origins and clinical significance of LDL heterogeneity

LDLs in humans comprise multiple distinct subspecies that differ in their metabolic behavior and pathologic roles. Metabolic turnover studies suggest that this heterogeneity results from multiple pathways, including catabolism of different VLDL and IDL precursors, metabolic remodeling, and direct production. A common lipoprotein profile designated atherogenic lipoprotein phenotype is characterized by a predominance of small dense LDL particles. Multiple features of this phenotype, including increased levels of triglyceride rich lipoprotein remnants and IDLs, reduced levels of HDL and an association with insulin resistance, contribute to increased risk for coronary heart disease compared with individuals with a predominance of larger LDL. Increased atherogenic potential of small dense LDL is suggested by greater propensity for transport into the subendothelial space, increased binding to arterial proteoglycans, and susceptibility to oxidative modification. Large LDL particles also can be associated with increased coronary disease risk, particularly in the setting of normal or low triglyceride levels. Like small LDL, large LDL exhibits reduced LDL receptor affinity compared with intermediate sized LDL. Future delineation of the determinants of heterogeneity of LDL and other apoB-containing lipoproteins may contribute to improved identification and management of patients at high risk for atherosclerotic disease.

Statins: mechanism of action and effects

The beneficial effects of statins are the result of their capacity to reduce cholesterol biosyntesis, mainly in the liver, where they are selectively distributed, as well as to the modulation of lipid metabolism, derived from their effect of inhibition upon HMG-CoA reductase. Statins have antiatherosclerotic effects, that positively correlate with the percent decrease in LDL cholesterol. In addition, they can exert antiatherosclerotic effects independently of their hypolipidemic action. Because the mevalonate metabolism generates a series of isoprenoids vital for different cellular functions, from cholesterol synthesis to the control of cell growth and differentiation, HMG-CoA reductase inhibition has beneficial pleiotropic effects. Consequently, statins reduce significantly the incidence of coronary events, both in primary and secondary prevention, being the most efficient hypolipidemic compounds that have reduced the rate of mortality in coronary patients. Independent of their hypolipidemic properties, statins interfere with events involved in bone formation and impede tumor cell growth.

Effects of low-dose pravastatin on plasma levels of lipids and apolipoproteins in Japanese type II hyperlipoproteinemic subjects with apolipoprotein E phenotype E3/2, E3/3, and E4/3

Effects of 12 weeks of treatment with pravastatin at a dose of 20 mg/day were compared in subjects with type II hyperlipoproteinemia with apo+(lipoprotein) E phenotype E3/2, E3/3, and E4/3. There were no differences in age, body mass index, smoking status, complications, or plasma levels of lipids and apoproteins, except the higher levels of apo E in E3/2 subjects (n = 11) than in E3/3 subjects (n = 84) and E4/3 subjects (n = 28). Plasma levels of low-density lipoprotein cholesterol (LDL-C) were reduced by 47% +/- 8% (mean +/- SD) in E3/2 subjects, 36% +/- 10% in E3/3 subjects, and 26% +/- 12% in E4/3 subjects after 12 weeks of treatment with pravastatin (all p < 0.0001). Plasma levels of apo B were decreased by 40% +/- 12% in E3/2 subjects, 27% +/- 10% in E3/3 subjects, and 18% +/- 14% in E4/3 subjects after 12 weeks of treatment with pravastatin (all p < 0.0001). The reduction in plasma levels of LDL-C and apo B was most marked in E3/2 subjects, next in E3/3 subjects, and smallest in E4/3 subjects. The authors conclude that treatment with pravastatin at a dose of 20 mg/day in Japanese subjects is equally effective as 40 mg/day in Western subjects, and apo Epolymorphism is a factor to determine the efficacy of pravastatin in Japanese subjects.

The influence of simvastatin on lipase and cholesterol esterase activity in the serum of men with coronary heart disease

Several studies have demonstrated that any beneficial effects of 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase inhibitors (statins), of which simvastatin (Merck Sharp & Dohme) is an example, on coronary events are linked to their hypocholesterolemic properties. The in vivo effects of simvastatin treatment on lipase (GEH = glycerol ester hydrolase) and cholesterol esterase (CEase) activity in the serum of men with coronary heart disease (CHD) were examined. GEH and CEase activity in the serum of men with CHD, before simvastatin treatment, was lower than in the control subjects. In our study we have provided evidence that simvastatin increases GEH activity in a time-dependent manner, but has no effect on CEase activity. This suggests that simvastatin can directly affect acylglycerol metabolism by an increase in GEH activity and may therefore be suitable for the treatment of combined lipoprotein disorders characterized by elevation of triacylglycerols.

Evaluation of coronary risk factors in patients with heterozygous familial hypercholesterolemia

Age at onset of clinically manifested coronary artery disease (CAD) varies widely among patients with familial hypercholesterolemia (FH). A number of factors in addition to high low-density lipoprotein cholesterol (LDL) have been suggested as predictors of risk among patients with FH, but a comprehensive examination of their utility is lacking. We therefore measured plasma lipids, carotid intima-medial thickness, and a variety of coronary risk factors in 262 patients with FH > or = 30 years old (68 of whom had premature CAD). Age (p < 0.0001) and gender were the most important determinants of premature CAD risk, with men having 5.64 times the risk of women (p < 0.0001). In addition, cigarette smoking (odds ratio [OR] 2.71, p = 0.026), smaller LDL as determined by the LDL cholesterol/LDL apolipoprotein B ratio (OR 2.60, p = 0.014), and white blood cell count (p = 0.014) were also statistically significant risk factors. Lipoprotein(a) and the presence of xanthoma were associated with risk only in very early coronary cases. After correction for age, carotid intima-media thickness was not associated with CAD risk. Insulin, fibrinogen, homocysteine, plasma C-reactive protein, and the angiotensin-converting enzyme insertion/deletion polymorphism were unrelated to risk in this cohort. These results provide little justification for extensive investigation of risk factors among patients with FH, at least for the risk factors examined here. Rather, the inherent high LDL cholesterol of these patients should be the focus of preventive efforts. The novel finding of increased risk with smaller LDL may prove useful but needs further confirmation.

Comparative effects of cerivastatin and fenofibrate on the atherogenic lipoprotein phenotype in proteinuric renal disease

Patients with nephrotic-range proteinuria have impaired clearance of triglyceride-rich lipoproteins. This results in the atherogenic lipoprotein phenotype (mild hypertriglyceridemia, low high-density lipoproteins [HDL], and excess small, dense low-density lipoproteins [LDLIII]). Excess remnant lipoproteins (RLP) are linked to hypertriglyceridemia and may contribute to the atherogenicity of nephrotic dyslipidemia. A randomized crossover study compared the effects of a statin (cerivastatin) and a fibrate (fenofibrate) on LDLIII and RLP in 12 patients with nephrotic-range proteinuria. Cerivastatin reduced cholesterol (21%, P: < 0.01), triglyceride (14%, P: < 0.05), LDL cholesterol (LDL-C; 23%, P: < 0.01), total LDL (18%, P: < 0.01), and LDLIII concentration (27% P: < 0.01). %LDLIII, RLP-C, and RLP triglyceride (RLP-TG) were unchanged. Plasma LDLIII reduction with cerivastatin treatment correlated with LDL-C reduction (r(2) = 34%, P: < 0.05). Fenofibrate lowered cholesterol (19%), triglyceride (41%), very low-density lipoprotein cholesterol (52%), LDLIII concentration (49%), RLP-C (35%), and RLP-TG (44%; all P: < 0.01). Fenofibrate also reduced %LDLIII from 60 to 33% (P: < 0.01). HDL-C (19%, P: < 0.01) increased with fenofibrate treatment; LDL-C and total LDL were unchanged. The reduction in LDLIII concentration and RLP-C with fenofibrate treatment correlated with plasma triglyceride reduction (LDLIII r(2) = 67%, P: < 0.001; RLP cholesterol r(2) = 58%, P: < 0.005). Serum creatinine increased with fenofibrate treatment (14%, P: < 0.01); however, creatinine clearance was unchanged. LDLIII concentration was 187 +/- 85 mg/dl after cerivastatin treatment and 133 +/- 95 mg/dl after fenofibrate treatment. Cerivastatin and fenofibrate reduce LDLIII concentration in nephrotic-range proteinuria. However, atherogenic concentrations of LDLIII remain prevalent after either treatment. Fenofibrate but not cerivastatin reduces remnant lipoproteins. The two treatments seem to reduce LDLIII by different mechanisms, suggesting a potential role for combination therapy to optimize lowering of LDLIII and RLP.

Preventing, stopping, or reversing coronary artery disease--triglyceride-rich lipoproteins and associated lipoprotein and metabolic abnormalities: the need for recognition and treatment

A substantial number of treated patients with or at high risk for coronary artery disease continue to have fatal and nonfatal coronary artery events in spite of significant reduction of elevated levels of low-density lipoprotein cholesterol. Other lipoprotein abnormalities besides an elevated level of low-density lipoprotein cholesterol contribute to risk of coronary artery disease and coronary artery events, and the predominant abnormalities that appear to explain much of this continued risk are an elevated serum triglyceride level and a low level of high-density lipoprotein cholesterol. Most patients with coronary artery disease have a mixed dyslipidemia with hypertriglyceridemia, which is associated and metabolically intertwined with other atherogenic risk factors, including the presence of triglyceride-rich lipoprotein remnants, low levels of high-density lipoprotein cholesterol, small, dense, low-density lipoprotein particles, postprandial hyperlipidemia, and a prothrombotic state. Aggressive treatment of these patients needs to focus on these other lipoprotein abnormalities as much as on low-density lipoprotein cholesterol. Combination drug therapy will usually be required. Reliable assessment of risk of coronary artery disease from lipoprotein measurements and response to therapy requires inclusion of all atherogenic lipoproteins in laboratory measurements and treatment protocols. At present this may be best accomplished by use of non-high-density lipoprotein cholesterol (total cholesterol minus high-density lipoprotein cholesterol) calculated from standard laboratory lipoprotein values. Ultimately, a more comprehensive assessment of coronary artery disease risk and appropriate therapy may include measurement of lipoprotein subclass distribution including determination of low-density lipoprotein particle concentration and sizes of the various lipoprotein particles.

The role of small, dense low density lipoprotein (LDL): a new look

Plasma low density lipoprotein (LDL) plays a central role in atherogenesis, and elevated levels of LDL are associated with an increased risk of coronary heart disease (CHD). Studies have now revealed that LDL is structurally heterogeneous, based on its size and density. Patients with combined hyperlipidemia exhibit a lipid profile - the so-called atherogenic lipoprotein phenotype - that is associated with elevated triglyceride levels, low levels of high density lipoprotein and a preponderance of atherogenic, small, dense LDL particles. Such individuals are at an increased risk of CHD events, regardless of their total LDL circulating mass. Evidence suggests that when plasma triglycerides exceed a critical threshold of approximately 133 mg/dl (1.5 mmol/l), this favours the formation of small, dense LDL from larger, less dense species. Lipid-lowering agents that are capable of lowering triglyceride levels below this threshold value will cause a shift to a less dense and, therefore, less atherogenic LDL profile. This effect has been demonstrated for the HMG-CoA reductase inhibitor atorvastatin which, in addition to its ability to markedly decrease the total LDL circulating mass, can also shift the LDL profile towards less dense, larger species. This suggests that atorvastatin may also affect the atherogenic lipoprotein phenotype found in patients with combined hyperlipidemia.

Effects of combination therapy with estrogen plus simvastatin on lipoprotein metabolism in postmenopausal women with type IIa hypercholesterolemia

We investigated the effects of estrogen and simvastatin, administered both alone and in combination, on the plasma lipid levels and lipoprotein-related enzymes in 45 postmenopausal women with type IIa hypercholesterolemia. They received 0.625 mg conjugated equine estrogen (n=15), 5 mg simvastatin (n=15), or the combination (n=15) daily for 3 months. We measured the concentrations of cholesterol and triglyceride in the plasma, and in the very low-density lipoprotein (VLDL), intermediate-density lipoprotein (IDL), low-density lipoprotein (LDL)1 (1.019<d<1.045 g/ml) and LDL2 (1.045<d<1.063 g/ml), and high-density lipoprotein (HDL)2 (1.063<d<1.125 g/ml) and HDL3 (1.125<d<1.210 g/ml) subfractions, and apolipoproteins, and the activities of lipoprotein-metabolizing enzyme before and after treatment. All three treatments significantly lowered the plasma levels of total cholesterol, LDL1 cholesterol, and apolipoprotein B, C-II, and E. In combination therapy, significantly reduced levels of VLDL, IDL, and LDL2 cholesterol were also obtained. Combination therapy lowered total and LDL1 cholesterol significantly more than did estrogen alone. Estrogen and combination therapy significantly increased the levels of cholesterol in the HDL2 subfraction, triglyceride in the HDL2 and HDL3 subfractions, and apolipoprotein A-I and A-II. Estrogen treatment, but not combination therapy, also significantly raised the levels of total and IDL triglyceride. Estrogen and combined therapies significantly lowered the activities of hepatic triglyceride lipase and lecithin cholesterol acyltransferase. Findings indicate that combination therapy with estrogen plus simvastatin favorably affected lipid metabolism by reducing the concentrations of VLDL and IDL particles as well as large and small LDL particles, increasing the concentration of HDL particles, and preventing estrogen-induced increases in plasma triglyceride levels.

Statins: effective antiatherosclerotic therapy

BACKGROUND

Statins are the most effective agents currently available for lowering plasma levels of low-density lipoprotein cholesterol (LDL-C) and are the mainstay of therapy for hyperlipidemia. The statins are highly liver-selective, inhibiting 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase, a key enzyme in the synthesis of cholesterol. Several large, controlled clinical trials have confirmed significant reductions in rates of coronary heart disease morbidity and death with long-term statin therapy in patients with mild to severe hypercholesterolemia.

METHODS AND RESULTS

This review article is based on a literature search of more than 60 relevant articles from peer-reviewed journals. Search engines included Medline and Embase. In surveying clinical and angiographic evidence, we found that statins appear to reduce the incidence of coronary events by slowing the progression of atherosclerosis and preventing atheromatous lesion formation. We found that the 6 statins currently marketed-atorvastatin, cerivastatin, fluvastatin, lovastatin, pravastatin, and simvastatin-differ in their inhibitory action on the HMG-CoA reductase enzyme.

CONCLUSIONS

The use of more potent statins such as atorvastatin and simvastatin affords greater lowering of LDL-C and triglyceride levels, allowing more patients to achieve target goals. The question of how low LDL-C levels should be lowered will be answered by ongoing clinical trials.

Hypocholesterolemic effects of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors in the guinea pig: atorvastatin versus simvastatin

Male Hartley guinea pigs were fed a hypercholesterolemic diet rich in lauric and myristic acids with 0, 10, or 20 mg/kg of simvastatin or atorvastatin for 21 days. Atorvastatin and simvastatin resulted in a lowering of plasma low-density lipoprotein (LDL) cholesterol in a dose-dependent manner by an average of 48 and 61% with 10 and 20 mg/kg, respectively. Both statins were equally effective in lowering plasma LDL cholesterol and apolipoprotein B (apo-B) levels. Atorvastatin and simvastatin treatments yielded LDL particles that differed in composition from the control. Due to the relevance of LDL oxidation and cholesteryl ester transfer in plasma to the progression of atherosclerosis, these parameters were analyzed after statin treatment. Atorvastatin and simvastatin treatment decreased the susceptibility of LDL particles to oxidation by 95% as determined by the formation of thiobarbituric acid reactive substances. An 80% decrease in the transfer of cholesteryl ester between high-density lipoprotein (HDL) and the apo-B-containing lipoproteins was observed after simvastatin and atorvastatin treatment. In addition, statin effects on plasma LDL transport were studied. Simvastatin- and atorvastatin-treated guinea pigs exhibited 125 and 175% faster LDL fractional catabolic rates, respectively, compared with control animals. No change in LDL apo-B flux was induced by either treatment; however, LDL apo-B pool size was reduced after statin treatment. Hepatic microsomal free cholesterol was lower in the atorvastatin and simvastatin groups. However, only atorvastatin treatment resulted in an 80% decrease of acyl-CoA:cholesterol acyltransferase activity (P < 0.001). In summary, atorvastatin and simvastatin had similar LDL cholesterol lowering properties, but these drugs modified LDL transport and hepatic cholesterol metabolism differently.

Plasma lipoprotein distribution and lipid transfer activities in patients with type IIb hyperlipidemia treated with simvastatin

The aim of the present study was to search in type IIb hyperlipidemic patients for putative concomitant effects of simvastatin on the physicochemical characteristics of low density lipoproteins (LDL) and high density lipoproteins (HDL), as well as on the activities of the cholesteryl ester transfer protein (CETP) and the phospholipid transfer protein (PLTP) that were determined in both endogenous lipoprotein-dependent and endogenous lipoprotein-independent assays. In a double-blind, randomized trial, patients received either placebo (one tablet/day; n = 12) or simvastatin (20 mg/day; n = 12) for a period of 8 weeks after a 5-week run-in period. Simvastatin, unlike placebo, reduced the lipid and apolipoprotein B contents of the most abundant LDL-1, LDL-2, and LDL-3 subfractions without inducing significant changes in the overall size distribution of LDL and HDL. Whereas simvastatin significantly increased PLTP activity in an endogenous lipoprotein-dependent assay (P < 0.01), no variation was observed in a lipoprotein-independent assay. Simvastatin significantly decreased plasma CETP activity in an endogenous lipoprotein-dependent assay (P < 0.01), and the reduction in plasma cholesteryl ester transfer rates was explained by a 16% drop in CETP mass concentration (P < 0.01). In contrast, the specific activity of CETP was unaffected by the simvastatin treatment reflecting at least in part the lack of significant alteration in plasma triglyceride-rich lipoprotein acceptors. The simvastatin-induced changes in plasma CETP mass levels correlated positively with changes in plasma CETP activity (r = 0.483, P = 0.0561), in total cholesterol levels (r = 0.769; P < 0.01), and in LDL-cholesterol levels (r = 0.736; P < 0.01). Whereas the observations suggest that simvastatin might exert concomitant beneficial effects on plasma CETP and LDL levels, neither plasma cholesteryl ester transfer activity nor plasma phospholipid transfer activity appeared as the main determinants of the LDL and HDL distribution profiles in type IIb hyperlipidemic patients.

Effect of 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitor on sterol absorption in hypercholesterolemic subjects

To investigate the potential effects of high-dose 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase inhibitor on plasma phytosterol, total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), and triglyceride (TG), hypercholesterolemic subjects received 40 or 80 mg/d simvastatin in a 24-week prospective clinical trial. Plasma lipid levels were analyzed enzymatically, and plasma phytosterol concentrations were determined using gas-liquid chromatography. The change in the plasma phytosterol-campesterol level was used as an indicator of cholesterol absorption in humans. Simvastatin treatment reduced plasma campesterol (-24%, P = .017) but did not affect circulating stigmasterol and sitosterol levels. A dose of 80 mg/d simvastatin produced a larger decrease (P = .050) in plasma campesterol (0.1680 mmol/L) than 40 mg/d (0.0237 mmol/L) versus baseline. There was a positive correlation between plasma campesterol and TC both before (r = .54, P = .027) and after (r = .63, P = .009) treatment. Plasma TC and TG levels did not differ between groups receiving 40 or 80 mg/d simvastatin. Simvastatin treatment reduced circulating TC, LDL-C, and TG by 40%, 50%, and 33% (P<.007), respectively. There was no significant effect of simvastatin on plasma HDL-C, but the HDL-C/LDL-C ratio increased 1.3-fold (P<.0001). In conclusion, this HMG-CoA reductase inhibitor reduces the plasma campesterol level, a marker of cholesterol absorption, which may contribute to the mechanism by which simvastatin decreases circulating cholesterol levels.

Lipid and lipoprotein concentrations in pregnancies complicated by intrauterine growth restriction

Previous studies have shown that in preeclampsia, plasma lipids climb substantially above levels seen in normal pregnancies. Such lipid changes may play a role in the endothelial damage characteristic of preeclampsia. Pregnancies complicated by intrauterine growth restriction (IUGR), without preeclampsia, have similar placental pathology to preeclampsia despite the absence of the maternal systemic manifestations of hypertension and proteinuria. The aim of this study was to perform a cross-sectional study of lipid and lipoprotein concentrations in the third trimester, from normal pregnancies, and those complicated by IUGR without preeclampsia. Our hypothesis was that, in contrast to the exaggerated lipid changes seen in preeclampsia, lipid and lipoprotein concentrations in IUGR would be similar to those of matched healthy pregnant controls. Fasting blood samples for lipids and lipoprotein fractions were taken in the third trimester, from eight women with IUGR; and eight women with uncomplicated pregnancies, matched as a group for age, booking weight, parity, and gestational age at sampling. There were no significant differences (P > 0.05) in the median concentrations of triglyceride, high-density lipoprotein, and very-low-density lipoprotein 1 (VLDL1), between cases and controls. However, women with IUGR pregnancies had significantly lower cholesterol [4.95 mmol/L (3.35-7.10) vs. 7.47 (5.75-8.45); median (range) for IUGR patients and controls, respectively; P < 0.01], low-density lipoprotein (LDL)-cholesterol [2.45 mmol/L (0.95-3.60) vs. 4.25 (3.35-5.60); P < 0.01], VLDL2 mass [59.0 mg/dL (37-87) vs. 103.0 (64-168); P < 0.01], intermediate-density lipoprotein mass [56.0 mg/dL (31-110) vs. 125.6 (91-157); P < 0.01], and total LDL mass [221.0 mg/dL (104-237) vs. 380.3 (267-534); P < 0.01]. In addition, it was noteworthy that, with respect to LDL-cholesterol and total LDL mass, there was little or no overlap in the ranges of concentrations measured between cases and controls. Because VLDL2 and intermediate-density lipoprotein are the synthetic precursors to LDL in the circulation, their significantly lower median concentrations imply a failure of appropriate LDL synthesis in IUGR pregnancies. Whatever the mechanism, if our results are confirmed in larger studies and longitudinal investigations, then LDL-cholesterol measurements (when LDL-cholesterol fails to rise appropriately or is low in the third trimester) may be of use in identifying mothers with, or at risk of, a pregnancy complicated by IUGR.

Association between low-density lipoprotein composition and its metabolism in non-insulin-dependent diabetes mellitus

Atheroma is related to low-density lipoprotein (LDL) composition. LDL in diabetic patients-a group with increased risk of severe atheroma-has been shown by our group and others to have various compositional alterations that are potentially atherogenic. Little is known about the relationship between LDL turnover and composition. This study examined the relationship between LDL composition and turnover in non-insulin-dependent diabetes mellitus (NIDDM) patients. Twenty-two NIDDM patients with a mean plasma cholesterol of 6.6+/-1.5 mmol/L were studied. Twelve subjects were hypercholesterolemic (mean cholesterol, 7.7+/-0.8 mmol/L), and eight of these agreed to be studied a second time after 4 weeks of treatment with simvastatin. LDL was isolated by density gradient ultracentrifugation, iodinated, and reinjected into the patient. LDL turnover was determined by measuring the clearance of [125I]-LDL from plasma over a 10-day period. The LDL residence time, determined using a biexponential model, correlated negatively with the body mass index (BMI) (r = -.73, P<.001) and serum triglycerides (r = - .57, P<.01). There was a significant inverse correlation between LDL residence time and the LDL esterified to free cholesterol ratio in hypercholesterolemic subjects (r = -.94, P<.001). There was a significant inverse relationship between LDL residence time and both hemoglobin A1c (HbA1c) and fasting blood glucose in these subjects before treatment (P<.005). After simvastatin therapy, the relationships were no longer significant. Simvastatin treatment was associated with a shorter LDL residence time (P<.01) and a decrease in LDL glycation (P<.001) with virtually no change in diabetic control (HbA1c, 6.0%+/-3.1% v. 6.3%+/-3.3%, NS). This study suggests that a decrease in residence time by upregulation of the LDL receptor with simvastatin alters LDL composition in a way that is likely to render the particle less atherogenic.

Metabolic modes of action of the statins in the hyperlipoproteinemias

Conflicting results have been published during the past few years regarding the physiologic modes of action of the hydroxymethylglutaryl-CoA (HMG-CoA) reductase inhibitors, generally referred to as statins, using standard doses. Three mechanisms have been described: increased LDL catabolic rate, increased removal of LDL precursors resulting in decreased LDL production and decreased VLDL production. The physiologic effects of statins seem to depend on the underlying pathology of the disorders under therapy. More recent data using either the more potent atorvastatin or larger doses of previously available statins (e.g. simvastatin 80-160 mg/day), suggest that both the potency of the statins and the underlying pathopHysiology are important in determining the predominant physiologic responses of patients. To understand physiologic responses more completely, drug-dose-physiologic response curves of apo B kinetics in various groups of patients are needed. Simultaneous studies of apo B, triglycerides and cholesterol metabolism are also needed and are currently feasible.