Reduction of Lp(a) by different methods of plasma exchange

Therapeutic efficiency of lipoprotein(a) reduction by low-density lipoprotein immunoapheresis

This study was performed to investigate the effect of low-density lipoprotein (LDL) immunoapheresis on lipoprotein(a) [Lp(a)] reduction in patients with heterozygous and homozygous familial hyperlipidemia (N=16) and insufficient response to lipid-lowering agents. By desorption of approximately 5,700+/-500 mL of plasma, a mean reduction in total cholesterol of 62% (P < .001) and in LDL-cholesterol of 70% (P < .001) was achieved. Lp(a), which was elevated at study entry in seven of these patients (82.1+/-34.3 mg/dL; range, 48 to 148 mg/dL), was reduced during the initial LDL-apheresis procedure by 74.8%+/-14.1% (P < .001). Long-term apheresis treatment performed at weekly intervals resulted in an mean reduction in Lp(a) pretreatment values to 39.1+/-28.5 mg/dL (-54%; P < .001). Desorbed Lp(a) was measured at the waste of the columns for 31 apheresis treatments. Lp(a) concentration of the column waste was higher in patients with elevated serum Lp(a) pretreatment values as compared with those with Lp(a) serum values within the normal range (elevated Lp(a), 1,420+/-380 mg; without elevated Lp(a), 235+/-190 mg; P < .001). The rate of return of Lp(a) following apheresis treatment scheduled at weekly intervals was comparable to that of LDL-cholesterol.

Lipoprotein(a) in renal disease

Lipoprotein(a) [Lp(a)] is a genetically determined risk factor for atherosclerotic vascular disease. Several studies have described a correlation between high Lp(a) plasma levels and coronary heart disease, stroke, and peripheral atherosclerosis. In healthy individuals Lp(a) plasma concentrations are almost exclusively controlled by the apolipoprotein(a) [apo(a)] gene locus on chromosome 6q2.6-q2.7. More than 30 alleles at this highly polymorphic gene locus determine a size polymorphism of apo(a). There exists an inverse correlation between the size (molecular weight) of apo(a) isoforms and Lp(a) plasma concentrations. Average Lp(a) levels are high in individuals with low molecular weight isoforms and low in those with high molecular weight isoforms. Mean Lp(a) plasma levels are elevated over controls in patients with renal disease. Patients with nephrotic syndrome exhibit excessively high Lp(a) plasma concentrations, which can be reduced with antiproteinuric treatment. The mechanism underlying this elevation is unclear, but the general increase in protein synthesis caused by the liver due to high urinary protein loss is a likely explanation. Patients with end-stage renal disease (ESRD) also have elevated Lp(a) levels. These are even higher in patients treated by continuous ambulatory peritoneal dialysis than in those receiving hemodialysis. Lipoprotein(a) concentrations decrease to values observed in controls matched for apo(a) type following renal transplantation. This clearly demonstrates the nongenetic origin of Lp(a) elevation in ESRD. Both the increase in ESRD and the decrease following renal transplantation are apo(a) phenotype dependent. Only patients with high molecular weight phenotypes show the described changes in Lp(a) levels. In patients with low molecular weight types the Lp(a) concentrations remain unchanged during both phases of renal disease. As in the general population, Lp(a) is a risk factor for cardiovascular events in ESRD patients. In this patient group the apo(a) phenotype seems to be equally or better predictive of the degree of atherosclerosis than is Lp(a) concentration. Further prospective studies will be necessary to confirm these observations. Whether Lp(a) also plays a key role in the pathogenesis and progression of renal diseases needs further study. Controversial data on the role of the kidney in Lp(a) metabolism result from insufficient sample sizes of several studies. Due to the broad range and skewed distribution of Lp(a) plasma concentrations, large study groups must be investigated to obtain reliable results.

Lipoprotein(a) in health and disease

Lipoprotein(a) [Lp(a)] represents an LDL-like particle to which the Lp(a)-specific apolipoprotein(a) is linked via a disulfide bridge. It has gained considerable interest as a genetically determined risk factor for atherosclerotic vascular disease. Several studies have described a correlation between elevated Lp(a) plasma levels and coronary heart disease, stroke, and peripheral atherosclerosis. In healthy individuals, Lp(a) plasma concentrations are almost exclusively controlled by the apo(a) gene locus on chromosome 6q2.6-q2.7. More than 30 alleles at this highly polymorphic gene locus determine a size polymorphism of apo(a). There exists an inverse correlation between the size (molecular weight) of apo(a) isoforms and Lp(a) plasma concentrations. The standardization of Lp(a) quantification is still an unresolved task due to the large particle size of Lp(a), the presence of two different apoproteins [apoB and apo(a)], and the large size polymorphism of apo(a) and its homology with plasminogen. A working group sponsored by the IFCC is currently establishing a stable reference standard for Lp(a) as well as a reference method for quantitative analysis. Aside from genetic reasons, abnormal Lp(a) plasma concentrations are observed as secondary to various diseases. Lp(a) plasma levels are elevated over controls in patients with nephrotic syndrome and patients with end-stage renal disease. Following renal transplantation, Lp(a) concentrations decrease to values observed in controls matched for apo(a) type. Controversial data on Lp(a) in diabetes mellitus result mainly from insufficient sample sizes of numerous studies. Large studies and those including apo(a) phenotype analysis came to the conclusion that Lp(a) levels are not or only moderately elevated in insulin-dependent patients. In noninsulin-dependent diabetics, Lp(a) is not elevated. Conflicting data also exist from studies in patients with familial hypercholesterolemia. Several case-control studies reported elevated Lp(a) levels in those patients, suggesting a role of the LDL-receptor pathway for degradation of Lp(a). However, recent turnover studies rejected that concept. Moreover, family studies also revealed data arguing against an influence of the LDL receptor for Lp(a) concentrations. Several rare diseases or disorders, such as LCAT- and LPL-deficiency as well as liver diseases, are associated with low plasma levels or lack of Lp(a).

Lipoprotein (a)

Lipoprotein (a) is similar to low-density lipoprotein but is unique in having an additional apolipoprotein called apolipoprotein (a) (apo(a)) covalently linked to it. apo(a), which is a member of the plasminogen gene superfamily, has a protease domain which cannot be activated to cause fibrinolysis. Its sequence of kringles is much longer than that of plasminogen and there is remarkable genetic variation in its length. The consequent inherited differences in apo(a) molecular mass are largely responsible for the wide range of serum Lp(a) concentrations in different individuals with low levels predominating in Europid populations. Physiologically Lp(a) may participate in haemocoagulation or in wound-healing. Epidemiological evidence that it is a risk factor for atherosclerosis, particularly in populations with high serum LDL levels, has led to research to uncover its role in atherogenesis and thrombosis. Diseases such as renal disease, and probably atherogenesis and thrombosis. Diseases such as renal disease, and probably atherosclerosis itself, are associated with an increase in Lp(a) above its genetically determined level and it remains a subject of speculation as to whether such increases are as closely involved in atherothrombosis as are spontaneously high levels resulting from low-molecular-mass apo(a) variants.

Heparin extracorporeal LDL precipitation (HELP): an effective apheresis procedure for lowering Lp(a) levels

Heparin-induced extracorporeal low-density lipoprotein precipitation (HELP) is based on the precipitation of apolipoprotein B (apo B) containing lipoproteins with heparin at low pH (4.85). In in vitro experiments we could show that Lp(a) is quantitatively (> 99%) precipitated from plasma by heparin in the pH range 4.6-5.2. The acute changes in Lp(a) after a single HELP-LDL apheresis were investigated in twelve patients with Lp(a) concentrations > 30 mg/dl. A single treatment caused a highly significant decrease (62%) in the concentration of Lp(a), similar to the decrease (60%) observed for LDL-cholesterol. Analysis of the data from ten patients with different apo(a) phenotypes indicated that Lp(a) is eliminated with almost 100% efficiency in the extracorporeal circulation, irrespective of apo(a) phenotype and plasma concentration. The mean rate of recovery of Lp(a) following HELP-LDL apheresis was slightly slower than that of LDL-cholesterol. Plasma Lp(a) concentrations were monitored in seven patients over 2 years. Mean Lp(a) concentrations after 2 years were lower than pre-treatment levels, indicating that repeated elimination of the lipoprotein does not lead to an induction in its synthesis. HELP-LDL apheresis should be particularly suitable for treatment of patients with elevated LDL-cholesterol levels who are also at increased coronary risk because of high Lp(a) concentrations.

Relation of lipoprotein(a) to coronary heart disease and duplexsonographic findings of the carotid arteries in heterozygous familial hypercholesterolemia

In familial hypercholesterolemia (FH) elevated Lp(a) concentrations are more frequent than in the general Caucasian population, but the clinical relevance of Lp(a) as a risk-factor in this group of patients is controversial. In 91 adult patients with heterozygous FH due to LDL-receptor defect we analyzed the correlation between Lp(a) concentrations, presence of coronary heart disease (CHD) and degree of atherosclerosis of the carotid arteries assessed by duplex scan. Coronary heart disease was present in 32 patients (24 males, 8 females). In the group without CHD the median of the Lp(a) distribution was 23 mg/dl, in the group with CHD 43 mg/dl (P < 0.05). The median of Lp(a) was 8 mg/dl in patients without pathological changes in the duplex scan of the carotids, 13 mg/dl in the group with intimal thickening, 25 mg/dl in patients with non-obstructing plaques, and 45 mg/dl in presence of > 30% luminal obstruction (P < 0.01). The role of Lp(a) as an independent risk factor was analyzed by stepwise logistic regression together with age, sex, LDL-, HDL-cholesterol, serum triglycerides, smoking status and presence of hypertension. For the prediction of CHD only age, HDL cholesterol and gender reached statistical significance. Lp(a) was, however, the lipoprotein parameter with the highest discriminative strength for the presence of a pathological duplex scan (P = 0.016), followed by LDL- (P = 0.03), and HDL-cholesterol (P = 0.03). These results provide direct evidence for a close correlation between Lp(a) and the rate of progression of atherosclerosis in FH, already at early, asymtomatic stages.

Reduction of lipoprotein(a) by LDL-apheresis using a dextran sulfate cellulose column in patients with familial hypercholesterolemia

Lipoprotein(a) (Lp(a)) was eliminated by LDL-apheresis using a dextran sulfate cellulose column in 3 homozygous and 10 heterozygous familial hypercholesterolemic patients. Immediately after LDL-apheresis by the LA-15 system (continuous LDL apheresis), there were significant reductions in Lp(a) concentrations (28.6 +/- 11.8 mg/dl (mean +/- S.E.) to 9.6 +/- 5.6 mg/dl (P < 0.01)), and in LDL-cholesterol concentrations (156 +/- 32 mg/dl to 48 +/- 18 mg/dl (P < 0.01)). Immediately following LDL-apheresis, Lp(a) and LDL-cholesterol were reduced by 67.4% +/- 11.6% and 68.3% +/- 11.8%, respectively. The removal of Lp(a) paralleled that of LDL-cholesterol. The reduced levels of Lp(a) nearly returned to baseline within 7 days. In 6 of the heterozygous FH patients the rates of recovery of LDL cholesterol and Lp(a) were calculated, according to Apstein's equation after discontinuing lipid altering drug treatment for 4 weeks. Mean constant k values of LDL cholesterol and Lp(a) were 0.354 (range: 0.136-0.752) and 0.427 (range 0.112-0.933), respectively. The average concentration during the 7 days following LDL-apheresis was calculated. Average reductions were 28% in LDL cholesterol and 18% in Lp(a). Pravastatin treatment, which continued for 4 weeks, significantly decreased LDL cholesterol (P < 0.01); however, before LDL-apheresis pravastatin treatment significantly increased Lp(a) levels (P < 0.05) in a small number (n = 6) of the FH patients, who had been regularly treated with LDL-apheresis. These results suggest that LDL-apheresis using the dextran sulfate cellulose column is an effective treatment to reduce levels of serum Lp(a) and LDL proportionally. This therapy may be of value in the prevention and regression of coronary artery disease in FH patients.

The HELP-LDL-apheresis multicentre study, an angiographically assessed trial on the role of LDL-apheresis in the secondary prevention of coronary heart disease. I. Evaluation of safety and cholesterol-lowering effects during the first 12 months. HELP Study Group

Fifty-one patients with coronary heart disease (CHD) and LDL-cholesterol levels greater than or equal to 200 mg dl-1 despite diet and drug therapy have been recruited into an angiographically controlled, multicentre, two-year study to evaluate HELP-LDL-apheresis in the secondary prevention of CHD. There were five drop-outs in the first year and 46 patients completed one year of therapy. An average of 2.791 of plasma was treated per patient every 7.7 days. Treatment was well tolerated and the incidence of side effects was small (2.9% of treatments). Mean pre-/post-apheresis LDL-cholesterol levels decreased from 283/120 mg dl-1 at baseline to 207/78 mg dl-1 and 203/76 mg dl-1 after 6 and 12 months, respectively. Mean pre-/post-apheresis HDL-cholesterol levels rose significantly over the course of therapy from 40.5/36.6 mg dl-1 to 44.8/39.7 mg dl-1 and 48.2/41.3 mg dl-1 after 0, 6 and 12 months, respectively. No major derangement of pre-apheresis haemostasis nor of haematological or clinical chemical parameters had occurred after 12 months of treatment. The data from this study support the feasibility of HELP-LDL-apheresis as an adjunctive therapy for lowering cholesterol levels in CHD patients refractory to cholesterol-lowering drugs while substantially improving the HDL/LDL ratio.

LDL-apheresis: results of longterm treatment and vascular outcome

LDL-apheresis (immunoabsorption, heparin precipitation (HELP), dextran sulfate cellulose binding (DSC) or filtration) is a potent therapeutic tool in familial hypercholesterolemia (FH) to eliminate LDL-cholesterol, Lp(a) or fibrinogen from the circulation and improve blood rheology. Repetitive use can deplete the cholesterol pool between 40 and 80%. As first reports showed, progression of coronary atherosclerosis can be stopped and sometimes regression can be induced. So far the domain of plasmapheresis was homozygous familial hypercholesterolemia. With several apheresis methods now available, it seems timely to define the indication of plasma therapy for heterozygous FH and the place of this potent therapeutic tool in primary and secondary prevention of atherosclerotic coronary heart disease in patients suffering from severe hypercholesterolemia resistant to diet and/or drug therapy.

Short- and long-term effects of LDL-apheresis on lipoprotein (a) serum levels

The effect of two extracorporeal elimination procedures for LDL on lipoprotein (a) concentrations in serum was studied in patients with heterozygous familial hypercholesterolemia. During a single apheresis serum lipoprotein (a) levels fell by 45% and 58%. Over a long-term period with weekly elimination lipoprotein (a) concentrations were lowered significantly by 43% (after 10-50 treatments) and 30% (after 51-99 treatments) compared to pre-treatment values. The rise during the week following apheresis was comparable to the corresponding reincrease of LDL-cholesterol and apolipoprotein B. We conclude that both apheresis techniques are very effective in reducing lipoprotein (a) serum levels.