Therapeutic effects of LDL apheresis in the prevention of atherosclerosis

LDL-apheresis: technical and clinical aspects

The prognosis of patients suffering from severe hyperlipidemia, sometimes combined with elevated lipoprotein (a) levels, and coronary heart disease refractory to diet and lipid-lowering drugs is poor. For such patients, regular treatment with low-density lipoprotein (LDL) apheresis is the therapeutic option. Today, there are five different LDL-apheresis systems available: cascade filtration or lipid filtration, immunoadsorption, heparin-induced LDL precipitation, dextran sulfate LDL adsorption, and the LDL hemoperfusion. There is a strong correlation between hyperlipidemia and atherosclerosis. Besides the elimination of other risk factors, in severe hyperlipidemia therapeutic strategies should focus on a drastic reduction of serum lipoproteins. Despite maximum conventional therapy with a combination of different kinds of lipid-lowering drugs, sometimes the goal of therapy cannot be reached. Hence, in such patients, treatment with LDL-apheresis is indicated. Technical and clinical aspects of these five different LDL-apheresis methods are shown here. There were no significant differences with respect to or concerning all cholesterols, or triglycerides observed. With respect to elevated lipoprotein (a) levels, however, the immunoadsorption method seems to be most effective. The different published data clearly demonstrate that treatment with LDL-apheresis in patients suffering from severe hyperlipidemia refractory to maximum conservative therapy is effective and safe in long-term application.

The effect of wet cupping on serum lipid concentrations of clinically healthy young men: a randomized controlled trial

OBJECTIVE

The aim of this study was to determine if a reduction in serum lipoproteins, especially LDL cholesterol, is a preventive approach against atherosclerosis. Phlebotomy has been a recommended method to reduce serum lipoprotein levels. The present study was conducted to investigate the effects of wet cupping on serum lipoprotein concentrations.

SUBJECTS AND METHODS

In this randomized controlled trial, 47 men (18 to 25 years old), without chronic disease or a history of hyperlipidemia and antihyperlipidemic drug consumption were randomly assigned into control (N = 24) and treated (N = 23) groups. Men in the treated group were subjected to wet cupping, whereas men in the control group remained untreated. The serum concentrations of lipids, collected from brachial veins, were determined at the time of wet cupping and then once a week for 3 weeks. Data were analyzed using a repeated measure ANOVA.

RESULTS

A substantial decrease in LDL cholesterol (p < 0.0001) and in the LDL/HDL ratio (p < 0.0001) was found in the treated group compared to the control. There were no significant changes in serum triglyceride between groups (p > 0.05). Although there were no statistically significant variations in total cholesterol and HDL cholesterol (p > 0.05), a 7% decrease in total cholesterol and 3% increase in HDL cholesterol may be clinically important.

CONCLUSIONS

Wet cupping may be an effective method of reducing LDL cholesterol in men and consequently may have a preventive effect against atherosclerosis.

Clinical applications of long-term LDL-apheresis on and beyond refractory hypercholesterolemia

Premature coronary heart disease (CHD) can result from high LDL cholesterol levels even in the absence of any other risk factors. A striking example is found in children who have the homozygous form of familial hypercholesterolemia (FH) with extremely high levels of LDL-cholesterol, and severe atherosclerosis and CHD often develop during the first decades of life. LDL-apheresis was developed for the treatment of severe type of FH patients who are resistant to lipid-lowering drug therapy. Clinical efficacy and safety of the therapeutic tool which directly removes LDL from circulation have already been established in the treatment for refractory hypercholesterolemia in FH patients. The most recently developed method enables lipoproteins to be adsorbed directly from whole blood, using polyacrylate column. In addition to benefits derived from the stabilization or regression of arterial lesions, we highlight other possible clinical applications of LDL-apheresis. However, most of these clinical benefits came from case reports or retrospective studies. Mechanisms related these clinical improvement remain unclear, and prospective randomized controlled trials should be performed for the new clinical indications of LDL-apheresis.

Current management of severe homozygous hypercholesterolaemias

PURPOSE OF REVIEW

This review focuses on recent advances in the management of patients with homozygous familial hypercholesterolaemia, autosomal recessive hypercholesterolaemia and familial defective apolipoprotein B.

RECENT FINDINGS

Autosomal recessive hypercholesterolaemia has been described as a 'phenocopy' of homozygous familial hypercholesterolaemia. Although the clinical phenotypes are similar, autosomal recessive hypercholesterolaemia seems to be less severe, more variable within a single family, and more responsive to lipid-lowering drug therapy. The cardiovascular complications of premature atherosclerosis are delayed in some individuals and involvement of the aortic root and valve is less common than in homozygous familial hypercholesterolaemia. Apheresis is still the treatment of choice in homozygous familial hypercholesterolaemia and in autosomal recessive hypercholesterolaemia patients in whom maximal drug therapy does not achieve adequate control. In addition to the profound cholesterol-lowering effects of apheresis, other potentially beneficial phenomena have been documented: improved vascular endothelial function and haemorheology, reduction in lipoprotein (a) and procoagulatory status, and a decrease in adhesion molecules and C-reactive protein.

SUMMARY

Patients with severe homozygous hypercholesterolaemia illustrate the natural history of atherosclerosis within a condensed timeframe. Effective cholesterol-lowering treatment started in early childhood is essential to prevent onset of life-threatening atherosclerotic involvement of the aortic root and valve, and the coronary arteries. Noninvasive methods for regular monitoring of the major sites involved in the atherosclerotic process are necessary in patients with no symptoms or signs of ischaemia. Management of patients with severe homozygous hypercholesterolaemia continues to be a major challenge.

Genetically defined hyperlipidemia

The unraveling of genetic defects associated with disorders in lipid metabolism has contributed to the understanding of lipoprotein metabolism and the pathophysiological consequences of a particular mutation. The translation, however, of a single genetic defect into the individual's risk of cardiovascular disease and subsequent treatment strategies is an extremely complex issue that involves the identification of multiple additional determinants, including genetic, metabolic and environmental factors. The discovery of these factors, including genetic determinants of drug efficacy, provides insight into the interaction between regulatory systems traditionally thought to be unrelated and may, in the future, lead to a more complete diagnostic and therapeutic appreciation of the individual patient.

Dyslipidaemia

The lowering of serum cholesterol is increasingly recognised as essential in the prevention of coronary heart disease and other atherosclerotic disease. The success of statin trials and the need to deploy these drugs effectively in the population has led increasingly to the identification of many people whose serum cholesterol, triglycerides, and HDL-cholesterol require clinical assessment, and frequently treatment. Lipid disorders are mainly straightforward, but some are complex or resistant to simple treatment strategies. I have reviewed the clinical manifestations of disordered lipid metabolism (dyslipidaemia) and its management.

Long-term effect of low-density lipoprotein apheresis in patients with heterozygous familial hypercholesterolemia

Clinical efficacy and safety of the therapeutic tool which directly removes LDL particles from circulation (LDL apheresis) have already been established in the treatment for refractory hypercholesterolemia in patients with familial hypercholesterolemia (FH). Two clinical studies with event-based assessment have demonstrated remarkably beneficial outcomes of long-term LDL apheresis using dextran sulfate cellulose columns plus adjunctive cholesterol-lowering drug therapy in the prevention of cardiovascular events in heterozygous FH with coronary artery disease. The results of several studies with angiographic and ultrasound-based assessment indicate a possible role for LDL apheresis in restructuring and stabilization of atherosclerotic lesions. These clinical improvements caused by LDL apheresis in heterozygous FH support the efficacy and importance of aggressive cholesterol-lowering therapy for secondary prevention of atherosclerotic cardiovascular disease in hypercholesterolemic patients.

Changes in oxidative stress and microcirculation by low-density lipoprotein apheresis

Low-density lipoprotein apheresis (LDLA) leads to an improvement of microcirculation during the very early stages of treatment, and continued treatment may produce antiatherogenic effects in patients with peripheral arterial disease (PAD). Suppression of oxidative stress, improvement of endothelial functions and alteration in the action of vasoactive compounds may occur with the improvement of the rheological property of blood as a result of aggressive removal of atherogenic factors including LDL, possibly resulting in the suppression of development of atherosclerosis. As these effects of LDLA may ameliorate not only PAD but also ischemia in other organs, it is suggested that repeated LDLA prevents the progression of atherosclerotic diseases and probably improves the long-term prognosis of patients with PAD.

Extracorporal low-density lipoprotein elimination by immunoadsorption

Low-density lipoprotein (LDL) apheresis has proven its therapeutic usefulness in patients who suffer from coronary heart disease but cannot achieve LDL cholesterol concentrations defined by the National Cholesterol Education Program guidelines. Immunoadsorption was the first commercially available apheresis technique. It is based on affinity chromatography. As with other apheresis techniques, immunoadsorption has specific advantages and disadvantages. These have to be taken into account when selecting an apheresis technique for the individual patient.

A review on the diagnosis, natural history, and treatment of familial hypercholesterolaemia

BACKGROUND

Familial hypercholesterolaemia (FH) affects approximately 1 in 500 people (10 million world-wide) and the elevated serum cholesterol concentrations lead to a more than 50% risk of fatal or non-fatal coronary heart disease by age 50 years in men and at least 30% in women aged 60 years. Based on a systematic literature search, we review the natural history of FH, describe the diagnostic criteria, and consider the effectiveness of treatment.

METHODS

A comprehensive review was conducted of the literature on the diagnosis of FH, the morbidity and mortality related to treated and untreated FH, and the evidence on the effectiveness of treatment of FH in adults and children. Treatment options have changed since statin treatment became available, and we have not considered pre-statin therapy studies of treatment effectiveness.

FINDINGS AND DISCUSSION

A clinical diagnosis of FH is widely used, but a definitive diagnosis can be made by genetic screening, although mutations are currently only detected in 30-50% of patients with a clinical diagnosis. Under-diagnosis of FH has been reported world-wide ranging from less than 1% to 44%. The relative risk of death of FH patients not treated with statins is between three and fourfold but treatment is effective, and delays or prevents the onset of coronary heart disease. Early detection and treatment is important. Aggressive LDL therapy is more effective in the regression of the carotid intima media thickness than conventional LDL therapy. Diagnosis at birth is problematic, and should be delayed until at least 2 years of age. Statins are not generally recommended for the treatment of children up to adolescence. Resins may be used but poor adherence is a problem. Technical advances in mutation detection, and the identification of other genes that cause FH, are likely to have important implications for the cost effectiveness of genetic diagnosis of FH.

LDL apheresis

Low density lipoprotein (LDL) apheresis provides a safe and effective means of treating patients with homozygous familial hypercholesterolaemia (FH). It also has a role in preventing the progression of coronary artery disease in heterozygotes and others with severe dyslipidaemia who are refractory to or intolerant of high doses of lipid-lowering drugs. Established methods involve either adsorption of apolipoprotein B-containing lipoproteins by affinity columns containing anti-apolipoprotein B antibodies or dextran sulphate, or their precipitation at low pH by heparin, in each instance after first separating plasma from blood cells with a cell separator. The most recently developed method enables lipoproteins to be adsorbed directly from whole blood, using polyacrylate columns. All 4 methods have proved to be similarly efficient when used weekly or biweekly to lower LDL cholesterol and Lp(a) without unduly reducing HDL cholesterol. Economic constraints restrict the use of LDL apheresis to the treatment of potentially fatal disorders such as FH, where there is clear evidence of benefit compared with conventional therapy. Widening the indications to include the treatment of other dyslipidaemic disorders such as steroid-resistant nephrotic syndrome, post-transplant donor vessel disease, stroke and prevention of re-stenosis after coronary angioplasty requires evidence from controlled trials that is currently lacking.

Long-term stable correction of low-density lipoprotein receptor-deficient mice with a helper-dependent adenoviral vector expressing the very low-density lipoprotein receptor

BACKGROUND

Familial hypercholesterolemia (FH) that results from LDL receptor (LDLR) deficiency affects approximately 1 in 500 persons in the heterozygous state and approximately 1 in 1 million persons in the homozygous state. We tested a novel gene therapy strategy for the treatment of FH in a mouse model.

METHODS AND RESULTS

We delivered the VLDL receptor (VLDLR) to the liver of LDLR-deficient mice and compared the effect of a helper-dependent adenoviral vector with all viral coding sequences deleted (HD-Ad-mVLDLR) with a first-generation vector (FG-Ad-mVLDLR), an HD-Ad (HD-Ad-0) that contained no expression cassette, and dialysis buffer (DB). A single intravenous injection of HD-Ad-mVLDLR led to a lowering of plasma cholesterol that lasted >/=6 months. Acute liver toxicity (as measured with liver enzyme elevation) occurred after FG-Ad-mVLDLR but not after HD-Ad-mVLDLR, HD-Ad-0, or DB treatment. At 6 months, VLDLR was detected in the liver with Western blotting and with immunofluorescence staining only in HD-Ad-mVLDLR-treated mice. Aortic atherosclerosis was almost completely prevented in these animals.

CONCLUSIONS

HD-Ad-mediated intravenous delivery of VLDLR to hepatocytes is well tolerated. It produces long-term lowering of plasma cholesterol and prevents atherosclerosis development in LDLR-deficient mice. These data provide support for the feasibility and safety of this approach for therapy of human subjects.

Does therapeutic intervention achieve slowing of progression or bona fide regression of atherosclerotic lesions?

-This review focuses on the regression of atherosclerosis in humans and experimental animals. It highlights the difficulties to determine unequivocally whether with a given therapeutic intervention, such as diet, drugs, or apheresis, the progression of lesions was curtailed or bona fide regression of atherosclerotic lesions was achieved. It seems appropriate to mention that 2 very different ways to measure regression were used in experimental animals and in humans. Regression in animals was determined mainly in the aorta or coronary arteries isolated at post mortem, and the criteria used were degree of sudanophilia and/or aortic wall thickness and cellular composition or cholesterol content. In humans, the evaluation of regression relied mainly on quantitative coronary angiography. The literature of the past decade is reviewed selectively but not exhaustively, and in some instances, a brief historical overview is given.