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1 Heart Institute (InCor) University of Sao Paulo Medical School, Sao Paulo, Sao Paulo, Brazil
2 Heart Institute (InCor) University of Sao Paulo Medical School, Sao Paulo, Sao Paulo, Brazil; Faculty of Pharmaceutical Sciences, University of Sao Paulo, Sao Paulo, Sao Paulo, Brazil
* To whom correspondence should be addressed. E-mail: ramarans{at}usp.br.
The objective of this study was to evaluate the effects of exercise training on plasma removal of a cholesterol-rich nanoemulsion (LDE) that mimics 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 14C-cholesteryl ester was injected intravenously and plasma samples 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 when compared to 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 VO2peak, in trained subjects. Circulating oxidized LDL levels were lower in trained subjects compared to the sedentary group (9.0 ± 2.0 and 16.0 ±3.0 mU/L). LDE was also injected into control and LDL receptor gene knock-out mice submitted and not to training. Muscle LDE uptake percentage was increased in the trained mice when compared to the untrained mice (1.1 ± 0.8 and 0.2 ± 0.1, respectively, p < 0.0001), in the control group but not in the knock-out 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.
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