Lycopene: Actions

ANTIOXIDANT

The many conjugated double bonds of lycopene make it a powerful antioxidant and its activity in vitro is nearly twice as great as beta-carotene.

REDUCES LDL-CHOLESTEROL LEVELS AND LIPID OXIDATION

A significant 14% reduction in plasma LDL-cholesterol concentrations has been shown for a dose of 60 mg/day lycopene taken over 3 months by healthy volunteers. While the mechanism of action is unclear, in vitro testing suggests HMG-CoA reductase inhibition and enhancement of LDL receptor activity in macrophages. Lycopene also prevents oxidation of lipids and LDL cholesterol, according to a clinical study.

CHEMOPREVENTATIVE ACTIVITY

Anticancer activity of lycopene has been demonstrated in cell and tissue culture studies and animal tumour models. Lycopene appears to inhibit human cancer cell growth by interfering with growth factor receptor signalling and cell cycle progression without producing toxicity or apoptosis. In vitro and in vivo evidence supports the theory that antiproliferative activity is achieved by upregulation of a gene, connexin 43, which restores direct intercellular gap junctional communication, usually deficient in many human tumours. This restoration of normal intercellular gap junctional communication is associated with decreased proliferation. Investigation using animal models also suggests that lycopene may exert its chemopreventative effects by modulating lipid peroxidation and enhancing the activities of phase 2 enzymes, specifically those in the glutathione redox cycle. A cell culture study using endometrial, mammary and lung human cancer cells has identified that lycopene has stronger antiproliferative activity than alpha- and beta-carotenes.

Of special significance in prostate cancer prevention is the finding that lycopene interferes with local testosterone activation by reducing the expression of 5-alpha-reductase I in prostate tumours in a rat model. As a consequence, several androgen target genes in the tumours were drastically downregulated.

Lycopene: Other Actions

The Antioxidant Supplementation in the Atherosclerosis Prevention (ASAP) study showed that low plasma levels of lycopene were associated with an 18% increase in intima-media thickness (IMT) of the common carotid artery wall in men as compared with men in whom plasma levels were higher than median. Lycopene also shows anti-inflammatory activity.