Exercise and ageing can independently increase free radical production that may enhance the susceptibility of LDL to oxidation and create a more atherogenic LDL particle. This investigation was designed to examine exercise and ageing on the susceptibility of LDL subfractions to oxidation. Eleven aged (55 ± 4 years) and twelve young (21 ± 2 years) participants completed a progressive exercise test to exhaustion and within one week performed a 1 h bout of moderate intensity (65% VO(2max)) exercise. Blood was assayed for metabolites associated with lipid composition (total cholesterol, free cholesterol, triglycerides) and lipoprotein susceptibility to oxidation. Exercise increased small density (sdLDL) oxidation, independently of age (p < 0.05). However, sdLDL oxidation further increased 24 h post exercise in the aged group (p < 0.05). With regards to the changes in lipid components within LDL, free and total cholesterol and triglycerides in large buoyant (lbLDL) were all elevated 24 h post exercise in aged compared with young (p < 0.05 for all comparisons). There was a decrease in triglycerides in medium density (mdLDL) 24 h post exercise in the aged group (p < 0.05). The lipid composition of sdLDL, VLDL, HDL(2), HDL(3) and serum lipid hydroperoxides remained unchanged as a function of exercise and ageing (p > 0.05). Although regular exercise training is known to be protective against cardiovascular disease (CVD) onset, our data demonstrates that acute exercise can increase sdLDL oxidative susceptibility, and this is independent of age and regardless of a change in LDL lipid composition. However, age seems to be a determining factor with regards the susceptibility of sdLDL to oxidation 24 h following exercise.
Keywords: Atherosclerosis; LDL metabolism; cardiovascular disease; free radicals; oxidised lipids.