Low-density lipoprotein (LDL) apheresis reduces atherogenic and oxidative markers in uremic patients with hyperlipidemia

Long-term follow-up of circulating oxidative stress markers in patients undergoing lipoprotein apheresis by Direct Adsorption of Lipids (DALI)

OBJECTIVE

Beyond its well-established efficacy in lowering atherogenic lipids and lipoproteins, DALI (Direct Adsorption of Lipids) apheresis has been shown to have acute anti-inflammatory and endothelium-protective effects. In the present study, we investigated long-term effects of DALI procedures on circulating oxidative stress markers.

METHODS

Thirteen patients involved in the study underwent regular DALI apheresis for nearly two years. At sessions 1, 40 and 80 conventional lipid status and changes of systemic oxidative stress markers (oxidized LDL, anti-oxidized LDL antibodies, advanced oxidation protein products (AOPP), and myeloperoxidase (MPO)) were examined.

RESULTS

DALI procedure efficiently reduced atherogenic lipids/lipoproteins. On day three after apheresis lipid parameters returned to pre-apheresis values. They showed no tendency to increase or to decrease over time. No significant differences were found between 1st, 40th and 80th sessions. In a similar way, levels of oxidative stress biomarkers acutely decreased after apheresis sessions and rebounded on day three after apheresis. No significant differences were observed between sessions 1, 40, and 80.

CONCLUSION

DALI apheresis repeatedly decreases atherogenic lipid/lipoprotein profile and oxidative stress biomarker levels during each session. Among all investigated parameters no longitudinal effects over two years could be observed.

Oxidized low-density lipoprotein (oxLDL) plasma levels and oxLDL to LDL ratio - are they real oxidative stress markers in dialyzed patients?

AIMS

Dyslipidemia and oxidative stress are commonly present in patients during maintenance dialysis treatment. However, the significance of oxidized LDL (oxLDL) as a marker of oxidative stress in uremia is still unresolved. The aim of this study was to establish the role of oxLDL and oxLDL/LDL ratio as markers of lipoprotein abnormalities and oxidative stress in the dialyzed patients.

MAIN METHODS

Plasma oxLDL level was measured by ELISA, and oxLDL/LDL ratio was calculated in 106 dialyzed patients and 20 controls. The linkages between oxLDL, oxLDL/LDL ratio and lipid profile and oxidative stress markers malondialdehyde (MDA) and Cu/Zn superoxide dismutase (Cu/Zn SOD) levels were also analyzed.

KEY FINDINGS

OxLDL levels and oxLDL/LDL ratio were similar in hemodialyzed patients and controls, whereas these parameters were lower in peritoneally dialyzed patients when compared to healthy individuals. In contrast, both MDA and Cu/Zn SOD levels were significantly higher in uremics than in controls. oxLDL and oxLDL/LDL ratio positively correlated with lipid profile (except of HDL), whereas there were no positive associations between these parameters and both MDA and Cu/Zn SOD. Multiple regression analysis confirmed that increased oxLDL/HDL and TC/HDL ratios and total cholesterol levels are the parameters which independently predicted oxLDL in dialyzed patients. In the case of oxLDL/LDL ratio, the independent variables were oxLDL/HDL ratio, total cholesterol and HDL levels.

SIGNIFICANCE

oxLDL levels and oxLDL/LDL ratio seem to be the markers of lipoprotein abnormalities rather than the markers of oxidative stress in the population of dialyzed patients.

Role of lipid apheresis in changing times

During the last decades, LDL-apheresis was established as an extracorporeal treatment option for patients with severe heterozygous or homozygous familial hypercholesterolemia (FH) that is resistant to conventional treatment strategies such as diet, drugs, and changes in lifestyle. Nearly half a century ago, the first LDL-apheresis treatment was performed by plasma exchange in a child with homozygous FH. At the beginning of the 1970s, the clinical advantage of regular extracorporeal LDL-elimination was demonstrated in siblings suffering from homozygous FH. These findings encouraged researchers especially from Germany and Japan to develop extracorporeal devices to selectively eliminate LDL-cholesterol in the 1980s. Although the selectivity of the currently available LDL-apheresis devices is different, the efficacy of LDL-elimination during a single treatment is rather similar and ranges between 55 and 65 % of the pretreatment LDL plasma concentration.In the 1990s, the patients regularly treated by extracorporeal LDL-elimination, diet, and drugs were included in regression studies assessed by angiography. It was shown that the combined treatment with LDL-apheresis, diet, and drugs resulted in less progression of coronary lesions than drugs and/or diet alone. However, although a tendency was evident, results did not reach criteria for significance. During the last decade, apheresis registries were established to collect data on efficiency, safety, and clinical outcome of regular long-term LDL-apheresis. The evaluation of registry data will certainly permit further insights in the therapeutic benefit of this expensive and time-consuming therapeutic approach. Furthermore, the future of LDL-apheresis will depend upon the availability of highly efficient new drugs and molecular genetic approaches such as RNA silencing of the apoB gene, whereas the liver transplantation and gene therapy of the LDL-receptor deficiency will not replace LDL-apheresis in severe familial hypercholesterolemia in the near future.