In vitro effects of ?-tocopherol and ascorbic acid on antioxidant characteristics of HDL [?-Tokoferol ve askorbik asitin HDL'nin antioksidan özelligi üzerine in vitro etkileri]

Abstract

phospholipids in low density lipoproteins (LDL) and have a capacity on inhibition of oxidative modification. These antioxidant and antiinflammatory properties are as important as its cholesterol efflux function on inhibition of atherosclerosis. Contrary to it's known effects when HDL has lost it's functions, gains prooxidant properties. The purpose of our study was to investigate effects of antioxidant vitamins like ?-tocopherol and ascorbic acid on the prevention of the antioxidant characteristics of HDL against LDL oxidation in vitro. Materials and methods: 30 healthy young subjects plasma HDL's were obtained by dextran sulfate precipitation method. Then, oxidation prevention capacities of these HDL's (10 µg/ml) against LDL (50 µg/ml) were measured by spectrofluorometric method. Also same HDLs were added in to the four different test tubes and they were separately incubated for an hour with different concentrations of ?-tocopherol (1.5 mg/dl and 3 mg/dl which are pharmacological and high dose respectively) and ascorbic acid (1.4 mg/dl and 2.8 mg/dl which are pharmacological and high dose respectively). Then, oxidation prevention effects of HDL against 50 mg/ml LDL which are added to the tubes, were measured by spectrofluorometric method. Also, HDL, LDL, TG, Lp(a), Apo A1, Apo B, and hsCRP levels were measured in serum which are simultaneously obtained from subjects serum. Results: In vitro 1.5 mg/dl and 3 mg/dl ?-tocopherol addition onto HDL increased HDL score values (median values 1.09 and 1.10 respectively) compared to control (median value 0.87). Fluoresans unit values (HDL score values) > 1.0 indicated as prooxidant HDL; values < 1.0 indicated as antioxidant HDL. In this way ?-tocopherol increased prooxidant HDL's by dose independent manner (p<0.05). While low dose ascorbic acid (1.4 mg/dl) had no effect on antioxidant characteristics (median HDL score value 0.95), high dose (2.8 mg/dl) ascorbic acid addition caused increase on prooxidant HDL's (median HDL score value 1.05) compared to controls (median HDL score value 0.87, p<0.05). Conclusion: In vitro supplementation of ?-tocopherol without depending on dose and ascorbic acid with depending on dose caused a prooxidant effect increasing the oxidative characteristics of HDLs