Effects of policosanol treatment on the susceptibility of low density lipoprotein (LDL) isolated from healthy volunteers to oxidative modification in vitro

AIMS: The aim of this study was to investigate the effect of policosanol on the susceptibility of LDL-C to in vitro lipid peroxidation in human healthy volunteers. METHODS: The effect of policosanol (5 and 10 mg day(-1) on LDL-C oxidation was studied in a double-blind, randomized, placebo-controlled trial conducted in 69 subjects. LDL-C samples isolated at baseline and after 8 weeks were subjected to in vitro tests of LDL-C oxidation. We tested the susceptibility of LDL-C to lipid peroxidation in a cell-free system by the addition of copper ions as well as in a more physiological system, macrophage-mediated oxidation. RESULTS: At baseline all groups were well matched regarding all variables. After 8 weeks of therapy policosanol administered at 5 and 10 mg, significantly and in a dose-dependent manner increased the lag phase of conjugated diene generation (mean +/- s.d.) from 83.79+/-29.16 min to 94.90+/-25.50 min (5 mg day(-1)) and from 82.74+/-17.16 min to 129.89+/-35.71 min (10 mg day(-1)), while in the placebo group LDL-C oxidation did not change significantly. Policosanol (10 mg day(-1)), but not placebo, significantly decreased the rate of conjugated diene generation. Comparison with placebo after therapy also showed significant differences. Macrophage mediated-oxidation was also inhibited by policosanol as evident by measuring thiobarbituric acid reactive substances (TBARS). Policosanol (10 mg day(-1)) significantly lowered malondialdehyde (MDA) generation from 8.50+/-0.91 to 5.76+/- 1.01 nmol mg(-1) protein. Comparison with placebo after 5 and 10 mg day(-1) showed significant differences. Policosanol significantly lowered total cholesterol by 10.5% (5 mg day(-1)) and 12.4% (10 mg day(-1)) and LDL-C by 16.7% and 20.2%, respectively. Also, policosanol (10 mg day(-1)) increased HDL-C by 15.2%. Five subjects withdrew from the study, none because of adverse experiences. No clinical or blood biochemical drug-related disturbances were found. CONCLUSIONS: The present study demonstrated that policosanol administered within its therapeutic dosage for lowering cholesterol (5 and 10 mg day(-1)), decreased the susceptibility of LDL-C to lipid peroxidation in vitro.