α-Tocopherol induces proatherogenic changes to HDL2 & HDL3: an in vitro and ex vivo investigation

High density lipoproteins (HDL) have considerable potential for improving cardiovascular health. Additionally, epidemiological studies have identified an inverse relationship between α-tocopherol intake and cardiovascular disease, which has not been translated in randomised controlled trials.

This study assessed if increased α-tocopherol within HDL(2) and HDL(3) (HDL(2&3)) influenced their antiatherogenic potential. In the first of two in vitro investigations, the oxidation potential of HDL(2&3) was assessed when α-tocopherol was added following their isolation. In the second, their oxidation potential was assessed when HDL(2&3) were isolated from serum pre-incubated with α-tocopherol. Additionally, a 6-week placebo-controlled intervention with α-tocopherol assessed if α-tocopherol influenced the oxidation potential and activities of HDL(2&3)-associated enzymes, paraoxonase-1 (PON-1) and lecithin cholesteryl acyltransferase (LCAT).

Conflicting results arose from the in vitro investigations, whereby increasing concentrations of α-tocopherol protected HDL(2&3) against oxidation in the post-incubated HDL(2&3), and promoted HDL(2&3)-oxidation when they were isolated from serum pre-incubated with α-tocopherol. Following the 6-week placebo-controlled investigation, α-tocopherol increased in HDL(2&3), while HDL(2&3) became more susceptible to oxidation, additionally the activities of HDL(2&3)-PON-1 and HDL(2)-LCAT decreased.

These results have shown for the first time that α-tocopherol induces changes to HDL(2&3), which could contribute to the pathophysiology of cardiovascular disease.