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Author(s): Joyce J. Repa [1]; David J. Mangelsdorf (corresponding author) [2] Atherosclerotic cardiovascular disease is the leading cause of death in developed countries. Epidemiological studies have identified a variety of [...]

The in vivo effects on humans of quercetin were investigated by having five healthy volunteers ingest 225 g of fried onions. Quercetin belongs to a group of polyphenolic compounds called flavonoids, which are thought to have antioxidant properties. The study found that quercetin can be ingested from dietary sources to high enough levels to raise the overall antioxidant activity of the plasma. Quercetin, however, exhibits strong affinity for protein and offers no direct protective effect during low density lipoproteins oxidation.

The plasma kinetics of epicatechin from black chocolate was evaluated in a sample of eight apparently healthy males. The plasma concentrations of epicatechin and theobromine increased after chocolate consumption. The plasma kinetics of both substrates correlated well with the dose of chocolate. These indicated that epicatechin is absorbed from chocolate and is easily eliminated from plasma.

A tendency to increase the susceptibility of low density lipoprotein to oxidation was observed in a moderate fat diet rich in monounsaturated fat (MUFA-diet), compared to a moderate fat diet rich in polyunsaturated fat (PUFA-diet). A significant difference between the negative mean change in lag time to oxidation in the PUFA-diet group and the slightly positive mean change in lag time in the MUFA-diet group was also noted. These results indicate that the MUFA-diet would prove more beneficial to patients with impaired glucose tolerance than a PUFA-diet.

Oxidized low density lipoprotein (ox-LDL) is known to be important in atherogenesis. Phenolic compounds are found in dry extracts of red wine and have been shown to be strong reactive oxygen species scavengers. The effects of the red wine phenolic compound (RWPC) dietary supplementation without alcohol interference on the biochemical characteristics of LDL, the oxidative susceptibility of LDL and the antioxidant capacity of total plasma (Pl-AOC) were evaluated. The RWPC supplementation had an enhancing effect on P1-AOC which could be due to a phenolic compound action.

The consumption of trans-fatty acids has no effect on the susceptibility of low density lipoprotein (LDL) to oxidative modification in men. There is no difference in the conjugated dienes, lipid peroxides, and macrophage uptake or electrophoretic mobility of the LDL. Men fed on a partially hydrogenated fish oil diet have more vitamin E in their serum than those fed on a partially hydrogenated soybean oil diet or butterfat diet. The three diet groups do not show differences in LDL particle composition.

An in vitro study of the influence of fish oil and vitamin E supplementation on copper-catalyzed oxidation of low density lipoprotein (LDL) showed that fish oil increased the ability of LDL to undergo copper-catalyzed oxidazability while vitamin E resisted the process. Fish oil also increased the formation of conjugated dienes during oxidation. Vitamin E, on the other hand, increased the time required to reach the maximum amount.

Low-density lipoproteins (LDL) are well known for their role in the regulation of cholesterol within the body, and high levels of LDL cholesterol carry an increased risk for heart disease. However, LDLs also are involved in the synthesis and regulation of prostaglandins, which are important mediators of inflammation and immunological reactions. The body cannot manufacture prostaglandins without substances such as linoleic acid derived from the diet. Research has now shown that, not only do the LDLs carry the raw materials for prostaglandin synthesis, but they also play a role in the regulation of the process. The lipoproteins, which are laden with fatty raw materials, bind to cells via the LDL receptor. This molecule then initiates the uptake of the LDL and the fats into the cell. The presence of the raw material on the LDL stimulates the initiation of synthesis of prostaglandins in the presence of platelet-derived growth factor, a substance involved in wound healing. However, as the cell digests the LDL it has incorporated, fragments appear to inhibit PDH synthase, an important enzyme of prostaglandin synthesis. Therefore, the LDL and receptor complex play a role in both the stimulation and inhibition of prostaglandin synthesis. (Consumer Summary produced by Reliance Medical Information, Inc.)