Enhanced removal from the plasma of LDL-like nanoemulsion cholesteryl ester in trained men compared with sedentary healthy men

Abstract

The objective of this study was to evaluate the effects of exercise training on plasma removal of a cholesterol-rich nanoemulsion (LDE) that mimics low-density lipoprotein (LDL) lipid structure and binds to LDL receptors. LDE-derived cholesteryl ester plasma kinetics was studied in 24 exercise-trained and 20 sedentary male subjects. LDE labeled with [(14)C]cholesteryl ester was injected intravenously, and plasma samples were collected over a 24-h period to determine radioisotope decay curves. LDL cholesterol concentration was similar in both groups. Fractional clearance rate (FCR) of the nanoemulsion label was greater in the exercise-trained group compared with the sedentary group (0.138 +/- 0.152 and 0.0261 +/- 0.023 h(-1), respectively). A positive correlation was found (r = 0.60, P < 0.01) between FCR and peak O(2) consumption in trained subjects. Circulating oxidized LDL levels were lower in trained subjects compared with the sedentary group (9.0 +/- 2.0 and 16.0 +/- 3.0 mU/l). LDE was also injected into control and LDL receptor gene knockout mice submitted and not submitted to training. Muscle LDE uptake percentage was increased in the trained mice compared with the untrained mice (1.1 +/- 0.8 and 0.2 +/- 0.1, respectively, P < 0.0001) in the control group but not in the knockout animals, indicating that the LDL receptor is involved in the increased uptake elicited by exercise. These results show that exercise training increases LDE plasma removal, which in turn suggests that it also increases LDL receptors or LDL receptor activity.