Secretion of pre beta HDL increases with the suppression of cholesteryl ester transfer protein in Hep G2 cells

Prep HDL are small, protein rich lipoproteins that are predominantly compos ed of apo A-I, without apo A-II. Prep HDL are secreted from the liver as na scent HDL and/or are produced in the incubated plasma by cholesteryl eater transfer protein (CETP). However, the role of CETP in the secretion of HDL from the liver has yet to be determined. In the present study, we examined the effect of the suppression of hepatic CETP by antisense oligodeoxynucleo tides (ODNs) against CETP targeted to the liver on the secretion of apo A-I using a Hep G2 cell culture. The ODNs against CETP were coupled to asialog lycoprotein (ASOR) carrier molecules. which serve as an important method fo r the regulation of liver gene expression. Hep G2 cells were cultured in DM EM supplemented with 10% FBS. After 2 days, the medium was changed to DMEM with EGF and the cells were divided into three groups. The control group re ceived saline, while the sense group was mixed with the sense ODNs complex and the antisense group was mixed with the antisense ODNs complex. respecti vely. for 2 days. Both the hepatic CETP mRNA and the CETP mass in the mediu m in the antisense group decreased significantly more than in the sense and the control groups (CETP mass: 1.697 +/- 0.410 ng/mg cell protein vs. 2.36 7 +/- 0.22 and 2.360 +/- 0.139, n = 3 in each determination). In contrast, both the hepatic apo A-I mRNA and the ago A-I mass in the medium in the ant isense group were significantly higher than those in the sense and the cont rol groups (apo A-I mass; 1.877 +/- 0.215 mu g/mg cell protein vs. 1.213 +/ - 0.282 and 1.097 +/- 0.144, n = 3 in each determination). The increase in apo A-I was mainly due to the increase in prep apo A-I. These findings may partly explain why HDL and apo A-I increase in patients with CETP deficienc y, while also indicating the possibility that the original level of prep HD L is sufficient in such patients. (C) 1999 Elsevier Science Ireland Ltd. Al l rights reserved.