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Effect of melatonin and metabolites on copper-mediated oxidation of flow density lipoprotein
H Seegar1, A O Mueck, T H Lippert
1Dept. OB/GYN, University Tübingen, Germany.
Aims:
A prophylactic use of melatonin as an anti-ageing drug has recently gained public interest due to its radical scavenging property in vitro. The present study was designed to investigate a possible antiatherogenic effect of melatonin and its physiological metabolites by examining their action on the radical-initiated formation of oxidized LDL, which is known to possess a high atherogenic potency. The metabolites investigated were the precursors serotonin and N-acetyl-serotonin and the main breakdown product 6-hydroxymelatonin.
Methods:
The effect of the test substances on the in vitro oxidation of LDL (increase in conjugated diene formation) was investigated at concentrations of 1, 5, and 10 microM.
Results:
Melatonin increased the lag time of formation of oxidized LDL only at a concentration of 10 microM. In contrast, 6-hydroxymelatonin, serotonin and N-acetylserotonin as well as vitamin E showed inhibitory effects starting at 1 microM. Thus the antioxidative action of melatonin was negligible compared with the effect of its main metabolite, its precursors and of vitamin E.
Conclusions:
The present results indicate that the pineal hormone melatonin appears to have little antiatherogenic property as regards the oxidation of LDL. Its main breakdown product 6-hydroxymelatonin, however, inhibits LDL-oxidation comparable to vitamin E. The precursors of melatonin, N-acetyl-serotonin and serotonin may also play a role in the inhibition of LDL oxidation in vivo.