Does lycopene offer human LDL any protection against myeloperoxidase activity?

Dietary supplementation with green tea extract promotes enhanced human leukocyte activity

BACKGROUND

Leukocytes play a vital role in the host defence and inflammatory systems, the latter being responsible for the pathogenesis of a wide spectrum of acute and chronic diseases. Green tea is a popular beverage, which is consumed worldwide and its active ingredients are epicatechin derivatives, which possess distinct anti-inflammatory properties. The purpose of this study was to investigate if a green tea extract could enhance leukocyte function in humans.

METHODS

Volunteers were asked to take 300 mg of the green tea extract daily for 14 days and the capacity of circulating leukocytes to release both myeloperoxidase and lactoferrin was assessed. Whole blood from volunteers was stimulated with the bacterial peptide Formyl-Methionine-Leucine-Phenylalanine (fMet-Leu-Phe). Myeloperoxidase an enzyme that converts hydrogen peroxide to hypochlorous acid and is stored and secreted from the granules of neutrophils and monocytes and was measured as well as lactoferrin which is an iron-binding protein stored and secreted from the neutrophils. In conjunction the antioxidant capacity of the blood of the volunteers was also determined using a chemiluminescence method that measures the capacity of plasma to scavenge superoxide.

RESULTS

After 14 days of treatment there was a significant increase in the release of myeloperoxidase and lactoferrin when whole blood was stimulated with fMet-Leu-Phe (p<0.05), which activates a number of leukocytes including mature neutrophils and monocytes. This was mirrored by a significant increase in the total antioxidant status after 14 days of green tea ingestion (p0.05). After the "wash-out" period of 4 weeks, all parameters were consistent with those observed at the start of the trial (day 0). Treatment with the green tea extract also caused a slight but non-significant decrease in the number of circulating leukocytes, but the counts remained within published "normal" ranges for healthy human adults.

CONCLUSIONS

This study indicates that a green tea extract when taken as a dietary supplement for 14 days can increase the leukocyte activity and the total plasma antioxidant status and may have role to play in the prevention of inflammatory disease.

Can carotenoids attenuate vascular aging?

One of the main manifestations of vascular aging is the development of atherosclerotic lesions. These lesions become unstable and prone to rupture due to the formation of reactive oxygen species (ROS) that are produced by the inflammatory milieu in the atherosclerotic plaque. The carotenoids are a group of red, orange, or yellow pigmented polyisoprenoid hydrocarbons synthesized by prokaryotes and higher plants. Lycopene, lutein, and other carotenoids have anti-oxidant activity that attenuates the inflammatory atherosclerotic process and delays vascular aging. This ability improves endothelial function due to the increase in bioavailability of NO. Carotenoid consumption also improves the metabolic profile, decreasing the incidence of diabetes, lowering LDL levels, and improving blood pressure control. The beneficial metabolic effect is translated to improvement in atherosclerosis, which is characterized by a decrease in carotid intima-media thickness. The favorable anti-atherosclerotic effect of carotenoids was also demonstrated in cross-sectional population studies showing a positive correlation between low carotenoid levels and adverse cardiovascular outcome. However, carotenoid utilization failed to decrease major cardiovascular and cerebrovascular events in randomized control double blind trials. The main still unanswered question is: What is the therapeutic role of carotenoids in atherosclerotic disease? Is their anti-atherosclerotic effect restricted to primary prevention or can it alter the prognosis of existing cardiovascular and cerebrovascular diseases?