Implications
(i) Atherosclerosis, cardiovascular disease, injury process
Focus
(i) Oxidized LDL
(ii) Plasma lipids and lipoproteins
Models
(i) Screening
® animal model
Why LDL oxidation?
For several years it has been known that development of atherosclerosis is related to the level of the ”noxious” low-density lipoprotein (LDL). More recent studies have revealed that ultimate atherogenic agents are in fact modified, mainly oxidized, forms of LDL. Clinical studies have shown that LDL-peroxidation products (LDL-PP) are closely related to coronary, carotid and brachial atherosclerosis. Indeed, as an indicator of the risk of atherosclerosis and cardiovascular disease (CVD) LDL-PP clearly exceeds sensitivity and specificity of the common lipid markers MDA/TBARS. Therefore, focusing on LDL oxidation will not only help in diagnosis and follow up of treatment of CVD, but also enables targeted development dietary supplements for prevention or decreasing the risk of atherosclerosis and CVD.
Prevention of LDL oxidation in vitro
Tests:
(i) Direct prevention of LDL oxidation (conjugated dienes, LDL lag phase)
(ii) LDL-incorporation.
Aim: To find out (i) if the test compound can prevent oxidation of human LDL in vitro, and (ii) if the test compound can incorporate into LDL particles.
Procedure: Studies are performed with LDL fraction isolated from human plasma. Oxidation is induced by copper and quantified by the common diene conjugation method. Studies will be done with several concentrations of the test compound and repeated on separate days. The results will be presented as comparison of the potency of the test compound with that of a simultaneously tested known antioxidant. Incorporation of test compounds into LDL to study the effect on LDL stabilisation.
Animal model: in vivo LDL oxidation and development of atherosclerotic lesions
Tests:
(i) Level of oxidized LDL
(ii) Stability of LDL against chemically induced oxidation
(iii) Effect of test compounds on atherosclerotic lesions
Aim: To find out how the test substance/extract/phytopreparation affects LDL oxidation and the progression of atherosclerosis in experimental animals
Procedure: Knockout LDLR mice (lacking the LDL receptor), fed an atherogenic diet, are used as an experimental model for atherosclerosis. The test compound will be administered in feed or drinking water. The level of LDL oxidation (circulating oxidized LDL) will be analyzed in blood samples. Atherosclerotic lesions will be recorded in histopathological investigations.
Effects on LDL oxidation in human volunteers
Tests:
(i) Level of total cholesterol
(ii) Level of LDL cholesterol
(iii) Level of oxidized LDL
Aim: To find out how the test compound affects LDL oxidation (and other lipid risk factors) in human body.
Procedure: Human volunteers with modestly elevated serum cholesterol level will be given the test compound or placebo after twelve-weeks run-in period. Blood samples will be taken at one to two week intervals during the study, and analyzed for LDL oxidation and the conventional plasma lipids.