Atherosclerosis 151 2000 389 – 397
C3H apoE − − mice have less atherosclerosis than C57BL apoE − − mice despite having a more atherogenic serum lipid
profile
D.C. Grimsditch
a,
, S. Penfold
a
, J. Latcham
b
, M. Vidgeon-Hart
c
, P.H.E. Groot
a
, G.M. Benson
a
a
Department of Vascular Biology, SmithKline Beecham Pharmaceuticals, New Frontiers Science Park North
, Third A6enue, Harlow, Essex, CM
19 5
AD, UK
b
Department of Laboratory Animal Sciences, SmithKline Beecham Pharmaceuticals, The Frythe, Welwyn, Herts AL
6 9
AR, UK
c
Department of Safety Assessment, SmithKline Beecham Pharmaceuticals, The Frythe, Welwyn, Herts AL
6 9
AR, UK Received 29 March 1999; received in revised form 17 September 1999; accepted 23 September 1999
Abstract
Wild-type C57BL mice are known to be susceptible to diet-induced atherosclerosis, whilst C3H mice are resistant. We investigated the effect of these background strains on the hyperlipidaemia and atherosclerosis that develops in mice deficient in
apolipoprotein E apoE − − . Male and female apoE − − mice on C3HHeNHsd C3H and C57BL6J C57 backgrounds were fed atherogenic Western diet for 12 weeks. Serum cholesterol and triglyceride concentrations were measured and
atherosclerosis quantified in the aortic sinus. C3H apoE − − mice fed normal diet had 1.5 – 2 fold higher serum cholesterol levels than C57 apoE − − mice and 4 – 5 fold higher serum triglyceride concentrations. Feeding Western diet caused a 4 – 5 fold
increase in serum cholesterol in all mice, but levels of triglyceride were either attenuated or were unaffected in C3H apoE − − and C57 apoE − − mice, respectively. C3H apoE − − mice had approximately 2 fold higher serum cholesterol and 4 fold
higher triglyceride concentrations than the C57 apoE − − mice throughout the study. Serum triglyceride concentrations were 35 – 108 higher in male C3H apoE − − than female C3H apoE − − mice. Most of the lipids were present in the very low
density lipoprotein VLDLchylomicron fraction in both strains of mice whether they were fed normal or Western diet. Notwithstanding the lower plasma lipid concentrations, atherosclerotic lesion areas were more than 2-fold larger in C57
apoE − − than in C3H apoE − − mice males 68 9 11 × 10
3
vs 30 9 6 × 10
3
, females 102 9 12 × 10
3
vs 41 9 8 × 10
3
m m
2
, mean 9 SEM. © 2000 Elsevier Science Ireland Ltd. All rights reserved.
Keywords
:
Atherosclerosis; C3H; C57BL; Female; Lesion area; Male; Western diet www.elsevier.comlocateatherosclerosis
1. Introduction
Inbred normal mice are relatively resistant to the development of diet-induced atherosclerosis, and rather
extreme diets, enriched in saturated fat, cholesterol and bile salts have to be used to initiate this process.
Notwithstanding this disadvantage, the availability of numerous genetically well-defined inbred strains has
made the mouse an attractive species in which to search for genes linked with susceptibility for developing
atherosclerosis. The work of Paigen et al. [1,2] on many strains of inbred mice has established ranking in the
susceptibility for atherosclerosis as follows: C57BR cdJ \ C57LJ \ SMJ \ C57BL6J \ SWRJ \ C58J \
129J \ DBA2J \ AKRJ \ BALBc \ NZBBINJ, HRSJ, AJ, C3HHeJ, SJLJ, CBAJ. Normal C57BL
6J C57 mice are, therefore, more susceptible to diet- induced atherosclerosis than C3HHe C3H mice.
When fed a diet containing approximately 1 choles- terol and 15 fat, C57 mice develop small atheroscle-
Corresponding author. Tel.: + 44-1279-627023; fax: + 44-1279- 627049.
E-mail address
:
david –c–grimsditchsbphrd.com D.C. Grims- ditch
0021-915000 - see front matter © 2000 Elsevier Science Ireland Ltd. All rights reserved. PII: S 0 0 2 1 - 9 1 5 0 9 9 0 0 4 0 0 - 1
rotic lesions in the aortic root after only 7 weeks, whereas lesions are absent in C3H mice fed the same
diet for up to 1 year, although total serum cholesterol concentrations in C3H mice are usually higher than
those in C57 mice [1 – 3]. Differences in the susceptibil- ity of these strains to developing atherosclerosis has
been attributed to at least eight genes Ath1 – Ath8, for which the approximate gene loci have been iden-
tified [4].
The recent development of technology for gene si- lencing and gene transfer has generated many novel
strains of mice with much greater susceptibility to developing atherosclerosis. Among these the knockout
of the apoE gene has been shown to give one of the most severe atherogenic phenotypes. ApoE is a major
constituent of very low density lipoproteins VLDL and chylomicrons and is an important ligand for the
receptor mediated uptake of these lipoproteins from the blood into the liver, as reviewed by Hofker et al.,
[5].
Furthermore, apoE
is implicated
in HDL
metabolism and
reverse cholesterol
transport. ApoE − − mice were initially produced by two
groups [6,7]. The apoE − − mice were subsequently bred into the C57 background and have now been
studied extensively. ApoE − − mice have impaired clearance of cholesterol-ester enriched VLDL and chy-
lomicrons from the blood which results in hyperlipi- daemia and the development of atherosclerotic lesions
[5]. It is reported that apoE − − mice develop spontaneous lesions when fed normal chow diet and
this process is further accelerated by feeding a high fathigh cholesterol diet [6,8,9]. Complex lesions that
include a fibrous cap can be seen in mice as young as 15-weeks-old and these are not just confined to the
aortic sinus but are found in the aortic arch, the major branches of the aorta and the pulmonary and carotid
arteries. The atherosclerotic lesions of apoE − − mice exhibit a similar distribution, microscopic ap-
pearance and cellular composition to those found in humans [9].
As mentioned above, wild-type C57 mice are rela- tively susceptible to diet-induced atherosclerosis. For
the present study we have bred the apoE − − mu- tation into the C3H strain, which has a low suscepti-
bility for atherosclerosis, to address the question as to whether the apoE knockout is so dominant in its
effect on atherosclerosis that the difference in suscepti- bility between the C57 and C3H strains is lost. Here
we report the results of a study in which we compared plasma lipid and lipoprotein concentrations and the
amount of atherosclerosis that developed in the aortic root of C57- and C3H apoE − − mice fed a West-
ern-type diet. As female mice of the C57 strain are reported to be more susceptible to diet-induced
atherosclerosis than males, these studies were per- formed using both sexes [10].
2. Materials and methods
