Atherosclerosis 142 (1999) 301 – 307
Cholesteryl ester transfer protein gene expression during differentiation
of human preadipocytes to adipocytes in primary culture
Benoit Gauthier, Malcolm Robb, Ruth McPherson *
Lipoprotein and Atherosclerosis Group, Uniersity of Ottawa Heart Institute, Ottawa, K1Y 4E9 Canada
Received 26 March 1998; received in revised form 7 July 1998; accepted 14 August 1998
Abstract
The expression pattern of the CETP gene in relationship to that of LPL, adipsin, PPAR,C/EBP, ADD1/SREBP1 and actin
was examined by RT-PCR during differentiation of human fibroblastic preadipocytes to adipocytes in primary culture.
Preadipocytes were isolated from subcutaneous fat obtained from healthy female subjects undergoing mammary reduction
procedures, and induced to differentiate in culture. Morphologically, adipogenesis was confirmed by the accumulation of lipid
droplets in cells. We show that the gene encoding CETP is expressed in preadipocytes and is present throughout differentiation
as compared to LPL and adipsin which were detected in the majority of samples by day 2 or 3 of adipogenesis. The transcription
factors, PPAR, ADD1/SREBP1 and C/EBP were expressed by day 2, concomitant with the appearance of LPL and adipsin but
subsequent to the appearance of CETP. CETP mRNA was not detectable in human skin fibroblasts. These studies demonstrate
that CETP expression is induced at an early stage of commitment to the adipocyte lineage and may be activated by transcription
factor(s), which are not members of the PPAR, ADD1/SREBP1 or C/EBP families. © 1999 Elsevier Science Ireland Ltd. All
rights reserved.
Keywords: Cholesterol; Pre-adipocyte; Human adipocyte differentiation; CETP; LPL; Adipsin; C/EBP ; PPAR ; ADD1
1. Introduction
Human adipose tissue stores a significant amount of
total body cholesterol (greater than 25%) where, due to
high cholesteryl esterase activity, it is stored as free
cholesterol. Adipocytes are dependent on lipoproteins
as a source of cholesterol since cholesterol synthesis is
limited in these cells. Our laboratory has recently
demonstrated that cholesteryl ester transfer protein
(CETP), which has an established role in reverse choles-
terol transport, also promotes the selective uptake of
HDL-derived cholesteryl esters by human adipocytes
[1]. These findings indicate that CETP may play an
important role in human adipocyte cholesterol
homeostasis. Thus, molecular mechanisms governing
CETP gene expression in adipocytes are of major inter-
est. The human wildtype CETP (wtCETP) gene encom-
passes 16 exons [2]. A variant CETP cDNA has been
described which lacks exon 9 (9CETP) [3]. Signifi-
cantly, 9CETP lacks neutral lipid transfer activity in
the plasma compartment and appears to form an intra-
cellular heterodimer with wtCETP, impairing its secre-
tion [4]. In transgenic mice bearing the human wtCETP
gene with its natural flanking sequences (NFR), hyperc-
holesterolemia achieved by feeding a high cholesterol
diet or crossing into an apoE knockout background
resulted in a disproportionate increase in wtCETP
mRNA [5].
Abbreiations: CETP, cholesteryl ester transfer protein; LPL, lipo-
protein lipase; C/EBP, CAATT enhancer binding protein alpha;
PPAR, peroxisome proliferator-activated receptor gamma; ADD1,
adipocyte determination and differentiation-dependent factor 1;
HDL, high density lipoproteins; RT-PCR, reverse transcriptase poly-
merase chain reaction.
* Corresponding author. Present address: Lab H453, 1053 Carling
Ave, Ottawa, Canada K1Y 4E9. Tel. +1-613-761-5256; fax +1-613-
761-5281; e-mail: rmcphers@heartinst.on.ca.
0021-9150/99/$ - see front matter © 1999 Elsevier Science Ireland Ltd. All rights reserved.
PII:S0021-9150(98)00245-7