Hepatic neutral cytosolic
cholesteryl ester hydrolase (hncCEH) is a key
enzyme in the regulation of hepatic free
cholesterol (FC). In examining the effects of over-expression of this
enzyme on
cholesterol homeostasis, mice were infected with a recombinant adenovirus construct (AdCEH) of the rat hncCEH
cDNA driven by the human cytomegalovirus promoter. Cholesteryl
esterase and p-nitrophenylcaprylate (
PNPC)
esterase activities were measured in liver postmitochondrial supernatants at 1, 3, 7, and 11 d after
infection with AdCEH or a control virus expressing
beta-galactosidase (AdbetaGAL). The
PNPC esterase activity of AdCEH mice peaked threefold higher than controls on day 2, declining on subsequent days. In contrast, cholesteryl
esterase peaked eightfold higher than controls on day 3, indicating a shift in substrate selectivity of hncCEH. Hepatic FC peaked at 144% of controls, 7 d postinfection. The mRNAs for
cholesterol 7alpha-hydroxylase,
sterol 27-hydroxylase, and
HMG-CoA reductase decreased to 47, 46, and 58% of controls, respectively, on day 7, coinciding with peak FC concentrations. Coinciding with increased cholesteryl
esterase activity, hepatic esterified
cholesterol dropped precipitously from day 3 onward, to 11% of controls by day 11. Hepatic TAG levels also declined, consistent with the reported TAG
lipase activity of hncCEH. These results demonstrate elevation of FC and depletion of
cholesteryl esters by over-expression of hncCEH, which were resistant to compensatory responses by other
enzymes of
cholesterol homeostasis.