Cholesteryl Ester Transfer Protein (CETP) Expression Prevents Diet-Induced Atherosclerotic Lesions

in Male db/db Mice

Paul S. MacLean1, Joseph F. Bower1, Satyaprasad Vadlamudi1, Jody N. Osborne2, John F. Bradfield2, Hubert W. Burden3, William H.

Bensch4, Raymond F. Kauffman4, Hisham A. Barakat1

 Departments of Biochemistry1, Comparative Medicine2, and Anatomy and Cell Biology3, in the Brody School of Medicine, East Carolina University, Greenville, NC, 27858; Lilly Research Laboratories4, a

Division of Eli Lilly and Company, Indiannapolis, IN, 46285

Cholesterol Ester Transfer Protein• Structural Information

– Plasma glycoprotein, 4 glycosylation sites– 2.2 kb mRNA, alternative splicing

• Functional Information– Catalyzes the heteroexchange of neutral

lipids between the plasma lipoproteins• Can modulate the composition and

concentration of the lipoproteins.• Important role in Reverse Cholesterol Transport.

HDLHDL

CETPCETPHDLHDL VLDLVLDL

TGTG TGTG

CECE CECE

LDLLDL

CECE

LiverLiverTGTG

CECE

HTGLHTGL

TissuesTissues

TGTG

LPLLPL

LDLRLDLR

TissuesTissuesCECE

ABC1/ABC1/LCATLCAT

RCT

LDLRLDLR

CECESRBISRBI

CETP and Vascular Health?

• Anti-Atherogenic– Role in RCT,

clearing peripheral cholesterol.

– Foger et al, 1999; Zhong et al, 1996; Hayek et al, 1995; Breslow, 1995; Sakai et al, 1995; Hirano et al, 1995; Yamashita et al, 1995; Hennessy et al, 1993; Kinoshita et al, 1993; Stein et al, 1985; Morton, 1988.

• Pro-Atherogenic–Lowers HDL-C,

increases VLDL-C and LDL-C.

– Rittershaus et al, 2000; Okamoto et al, 2000; Mabuchi et al, 1995; Inazu et al, 1994; Marotti et al, 1993; Bhatnagar et al, 1993; Kinoshita et al, 1993; Agellon et al, 1992; Quinet et al, 1991.

Why Study CETP?

• Perturbations in CETP expression could lead to abnormal lipid/lipoprotein profiles and contribute to vascular disease.– Excess or deficiency in CETP expression

• CETP is viewed as a potential target in the treatment of vascular disease, a tool to modify atherogenic lipoproteins.– CETP inhibitors, activators

CETP and the Insulin Resistance Syndrome

• IRS – dyslipidemia, obesity, diabetes, insulin

resistance, vascular disease, hypertension, etc.• Alterations in CETP expression in IRS

– elevated in obesity– type 2 diabetes?

Plasma CETP Activity and Mass

50

55

60

65

70

75

80

85

90

Activity

nmol/

mL/hr

Values are given as means ± SEM (n). significantly different from the non-obese, p<0.001.significantly different from the obese, p<0.001.

1.5

1.75

2

2.25

2.5

Mass

ug/m

L

(129) (95) (25) (20)(42)(57)

Values are given as means ± SEM (n). significantly different from the non-obese, p<0.05.significantly different from the obese, p<0.05.

Non-Obese Obese Obese NIDDM

How does Type 2 Diabetes influence thecharacteristics of Obese Patients?

CVDRisk

over twice the risk

(Manson et al, 1990; Abbott et al, 1988)

LipidAbnormalities

TG, LDL-C, HDL-C

(Barakat et al, 1990; Barakat et al, 1992)

LipoproteinAbnormalities

LDLs, HDLs, VLDLs

(MacLean et al, 2000; Barakat et al, 1990-2)

PlasmaCETP Levels

~20% lower(MacLean et al, 2000; Kahri et al, 1994)

Purpose• To examine the effects of CETP

overexpression on vascular health in a murine model of

diabetic obesity (db/db).

Experimental Design

CETP(+/+ C/C)

db/CETP(db/db C/C)

db(db/db -/-)

AtherogenicDiet

16 Weeks

lesionsin the

proximal aorta

cholesterol distribution

amonglipoproteins

(+/db -/C)

(+/db -/C)

CETPLesions found in:

-

0/23 mice

dbLesions found in:

-

15/17 mice-

(26,098 ± 7486 m2)

db/CETPLesions found in:

-

0/22 mice

Plasma Total Cholesterol

0

200

400

600

0 30 60 90 120Days on Atherogenic Diet

mg/

dLCETPdbdb/CETP

0

100

200

300

400

500

600

15 20 25 30 35 40

Elution Time, min

Chol

resp

onse

, mV

CETPdbdb/CETP

VLDL IDL/LDL HDL

FPLC Cholesterol Subfractioning

VLDL and IDL/LDL Cholesterol

0

20

40

60

80

100

0 30 60 90 120Days on Atherogenic Diet

v-se

c

VLDL Cholesterol

0

7

14

21

28

35

0 30 60 90 120Days on Atherogenic Diet

v-se

c

IDL/LDL Cholesterol

CETPdbdb/CETP

Characteristics of the mice

Summary

• The overexpression of CETP in db/db mice:– lowers total cholesterol concentrations– lowers the amount of cholesterol in

VLDL and IDL/LDL subfractions– prevented the formation of diet-induced

atherosclerotic plaques

Conclusions

• In this murine model of diabetic obesity, CETP is clearly anti-atherogenic.

• In the metabolic context of diabetic obesity in humans, CETP may play an important role in maintaining vascular health.

• The suppressive effect of diabetes on CETP expression in obese humans may contribute to the higher risk of atherosclerosis.