Prolonged Inactivity Up-Regulates Cholesteryl Ester Transfer Protein Independently of Body Fat Changes in Humans

Abstract

Physical inactivity is associated with insulin resistance and decreased high-density lipoprotein (HDL) cholesterol. Cholesteryl ester transfer protein (CETP) is involved in cholesterol metabolism, being responsible for the transfer of cholesteryl esters from HDL to very low- and low-density lipoproteins. We hypothesized that physical inactivity could decrease HDL cholesterol through changes in CETP availability. Twenty-four healthy, male volunteers (aged 23.1 +/- 0.5 yr) were investigated in eucaloric conditions before and at the end of 35 d of experimental bed rest. Changes in body composition were monitored by bioimpedance throughout the study. Before and at the end of the experimental period, plasma insulin and glucose and plasma lipid pattern as well as CETP concentrations were determined. Our results demonstrated that during bed rest, fat mass did not change significantly, whereas fat-free mass decreased by 3.9 +/- 0.4% (P < 0.01). The homeostatic model assessment index of insulin resistance significantly (P < 0.001) increased by 47 +/- 11% after bed rest. Bed rest decreased HDL cholesterol by 12 +/- 3% (P < 0.05), increased triglycerides by 51 +/- 10% (P < 0.05), whereas it did not change significantly low-density lipoprotein cholesterol. Plasma CETP concentration increased after bed rest by 27 +/- 9% (P < 0.01). Bed rest-induced changes in CETP concentrations inversely correlated with changes in the ratio between HDL and non-HDL cholesterol (n = 24; R = -0.43; P < 0.05). Physical inactivity decreases HDL cholesterol, at least in part, through CETP up-regulation.