Plasma Lipid Composition and LDL Oxidation

Abstract

Low-density lipoprotein (LDL) oxidation in vivo depends on lipid composition and on plasma antioxidant status. The aim of our study was to investigate the relationship between plasma lipid composition and LDL oxidation and, in particular, to explore whether LDL-cholesterol/triglycerides ratio (LDL-C/TG) and LDL-cholesterol/high-density lipoprotein (HDL)-cholesterol ratio (LDL-C/HDL-C) can be used as predictive parameters of LDL oxidation in vivo. In 87 volunteers over a wide range of age plasma lipids and LDL oxidation were studied. Blood was collected after 12 h overnight fast. LDL oxidation was estimated by the level of conjugated diene (BDC) in the lipid fraction isolated from plasma after gradient ultra-centrifugation. The results were expressed as micromol/l (BDC/l) to evaluate the level of oxidized LDL, and as nmol of BDC for mg of LDL-cholesterol (BDC/LDL-C) for the evaluation of LDL oxidation degree. BDC/l correlated significantly with age, total and LDL-C, apolipoprotein B and TG, while BDC/LDL-C negatively correlated with total cholesterol, apolipoprotein B, LDL/TG and LDL/HDL ratios. Age of subjects significantly correlated with total and LDL-C and apolipoprotein B. TG have a significant inverse correlation with HDL-C. Our results support the hypothesis that among the several factors involved in LDL oxidation the most important determinants are LDL/TG. Plasma triglycerides appear to be very important even when circulating cholesterol levels are within normal limits. Moreover, we found that the LDL/HDL ratio is also very important with regard to the putative protective role of HDL against LDL oxidation in vivo. In conclusion, plasma lipid parameters must be evaluated not only for their absolute values but also for their mutual ratios as expression of plasma lipid homeostasis. Both LDL/TG and LDL/HDL ratios can be used as predictive parameters of in vivo LDL oxidation.

Intermittent cold-induced hippocampal oxidative stress is associated with changes in the plasma lipid composition and is modifiable by vitamins C and E in old rats

“…The present results on increased LDL-C/TG and LDL-C/ HDL-C ratios in animals exposed to cold are indicative of LDL oxidation in vivo with the former ratio being suggested as an important predictor of LDL oxidation (Brizzi et al, 2005). Although we have not measured the TCH in the hippocampus, studies by Cutler et al (2004) have documented increased TCH in old mice at 25 months of age, and have related the increase to similar situations of oxidative stress involving activation of sphingomyelinases resulting in ceramide production and accumulation of TCH, and have shown that a-tocopherol is effective in inhibiting the enzymes.…”

Anthropometrical parameters and markers of obesity in rats

“…On the other hand, increased serum TG concentrations have been associated with decreased LDL-C, which becomes more susceptible to oxidative modification (Brizzi et al 2003). It is widely accepted that atherogenesis is initiated by oxidation of the lipids in LDL-C (Chen et al 2003).…”

Impact of the Training Program on Lipid Profile and Cardiac Health

“…These observations indicated that over-training, as occurred in the TL group, accelerated the breakdown of HP and increased aldehyde production. These observations are substantially important in explaining the adverse alterations on serum lipids (1,4). Lipid hydroperoxides give rise to a large variety of products, many of which react with TBA and with serum lipids (1).…”