Prolonged inactivity up-regulates cholesteryl ester transfer protein independently of body fat changes in humans.
BACKGROUND
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.


OBJECTIVE
We hypothesized that physical inactivity could decrease HDL cholesterol through changes in CETP availability.


METHODS
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.


METHODS
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.


RESULTS
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).


CONCLUSIONS
Physical inactivity decreases HDL cholesterol, at least in part, through CETP up-regulation.
Mazzucco
Sara
S
Department of Medical, Technological, and Translational Science, Division of Internal Medicine, University of Trieste, 34139 Trieste, Italy.
Agostini
Francesco
F
Mangogna
Alessandro
A
Cattin
Luigi
L
Biolo
Gianni
G
D000273:Adipose Tissue / Q000378:metabolism; D001510:Bed Rest; D001823:Body Composition; D053480:Cholesterol Ester Transfer Proteins / Q000097:blood*; D008076:Cholesterol, HDL / Q000097:blood; D002149:Energy Intake; D005247:Feeding Behavior; D006801:Humans; D008019:Life Style; D008055:Lipids / Q000097:blood; D008297:Male; D017524:Slovenia; D018667:Tilt-Table Test; D015854:Up-Regulation; D055815:Young Adult
C506642:CETP protein, human; D053480:Cholesterol Ester Transfer Proteins; D008076:Cholesterol, HDL; D008055:Lipids