Influence of a lipogenic diet on the cholesterol synthesis in rats in vivo

Vol. 68, No. 2, 1976

INFLUENCE

OF A LIPOGENIC

Department

Received

BIOCHEMICAL

of

Vitamin

November

DIET

AND BIOPHYSICAL RESEARCH COMMUNICATIONS

ON THE CHOLESTEROL 0. Wiss *I

and

Nutritional

Co.

Ltd.,

SYNTHESIS

Research

Basle,

of

F.

IN RATS IN VIVO

Hoffmann-La

Roche

&

Switzerland

11,1975 SUMMARY

An inhibition of the cholesterol synthesis by a lipogenic diet in rat liver is described. The inhibition could be shown with glucose or mevalonate as tracer substances. This inhibition is located between lanosterol and cholesterol and results in a reduction of the cholesterol synthesis to about one sixth of the control group. No indication for any other inhibiting effect was obtained by these in vivo experiments. INTRODUCTION The the to

subject the

sults in

of

vitro

or

widely

synthesis

tween

1.1.1.34) of

for

a lipogenic

using labelled incorporation

based

cholesterol of

cholesterol

synthesis

Special

attention

feeding

in

experiments

isolated

enzymes.

a key that

fatty

acids

and

regulation

ketone

of

A and

role

in

the

by inhibition

The

the

bodies

According of

this

to a

are

assumed

Other

synthesis, to

exist

the

enzyme

hydroxy-methylglutaryl-coenzyme

squalene,

out

A reduct-

occurs.

cholesterol

re-

carried

regulation of

i;

was given

rats.

P-hydroxy-B-methylglutaryl-coenzyme

plays

and

the

publications. of

activities the

of

on incorporation

sense

the

regulation

of and

that

acetyl-coenzyme

but

cholest-

a shunt

to

inhibiting such

as be-

A or

between

to be of

minor

(1-j). In

of

theory,

intermediate

importance

number

mainly

in

the

fasting

on comparing

No.

influences this

are

synthesis

the

of

accepted (E.C.

erol

of

a great

influence obtained

ase

mechanism

this

communication,

diet

on the

results

cholesterol

glucose and mevalonate into squalene, lanosterol MATERIALS

are synthesis

reported by in

on the vivo

as precursors and and cholesterol.

influence

experiments,

by measuring

its

AND METHODS

Rats weighing 180-200 g were kept on a stock diet consisting of 60 % cereals, 18 % plant proteins, 4 % minerals and 1 % vitamin mixture. The experimental group received a lipogenic diet during a period of

*)

Present address: Vesalianum, Basle,

Institute Switzerland

Copyright 0 1976 by Academic Press, Inc. All rights of reproduction in any form reserved.

of Biochemistry,

350

University

of

Basle,

BIOCHEMICAL

Vol. 68, No. 2, 1976

AND BIOPHYSICAL RESEARCH COMMUNICATIONS

Table

1

dpm per glucose 10 pCi/30.5

(oral dose: pg in 0.5 ml)

Into

acetone

extract

Into

squalene

Into

cholesterol

Lipogenic Diet 6 rats

rat

Stock 6

268 400

Into

squalene

Into

lanosterol

*)

Before for 16

Lipogenic Stock

6-S 800

Diet: Diet

4.2

425

1.6

6 140

22 163

0.28

2

dpm per (oral

Diet rats

I I

682

Table

mevalonate dose: 5 pCi/l.7

1

liver

rat

liver

pg,

the administration hours.

of

the

load

dose,

the

rats

were

fasted

five days of the following composition: 70 % glucose, 24 76 vitamin-free casein, 5 % minerals, and 1 % vitamin mixture. D-fi-lhC]glucose with specific activity of 324 pCi/mg and DL-D-3H/ mevalonic acid lactone a specific activity of 3.85 mCi/mg were administered by stomach tube the morning. Two hours later, the animals were sacrificed by taking that the intervals between the application of the tracer substances the removal of the liver were the same for each animal.

a with in care and

Liver homogenate was used for extraction. The saponification was carried out with equal quantities of homogenate and 30 % methanolic KOH under reflux at 100°C during 30 min. The unsaponifiable was chromatographed on alumina I inactivated with 7 % water. The various fractions were eluted with petroleum ether/ether mixture 100/O for squalene, 95/5

351

Vol. 68, No. 2, 1976

BIOCHEMICAL

AND BIOPHYSICAL

RESEARCH COMMUNICATIONS

for lanosterol and 80/20 for cholesterol. The substances were identified by determination of the molecular weight with mass spectroscopy. It turned out that the lanosterol fraction contained some dihydrolanosterol. RESULTS It in

rat

is

glucose-rich one

of

the

fourth

ivity the

was to be expected

livers

oration

cholesterol

lanosterol

is

pathway

ly

located

of

(Table

As the inhibited that 1).

was used

synthesis

between

activated

by the

lipogenic

between

lanosterol

and

the

lipids

a lipogenic,

became

further and, 2).

only

of

mevalonate

and

located

evaluation

of

in

clear that

into

and

the its

out

that

reduced

that the

addition,

turned

slightly

mevalonate

diet

is

It

is

thus

of radioactincreased by

inhibition

(Table

incorporation It

of

as tracer

mevalonate

enhanced.

total

incorporation but even

For

was measured from

the

not

the

a strong reduction of the incorpcholesterol is observed to about

be concluded

mevalonate

steroid

is

of

administration

into

group.

cholesterol

whereas

synthesis

however, glucose

squalene

lanosterol

strongly

the

by the

control

must

synthesis

diet,

the

and into

lipogenic

siderably

it

mechanism

incorporation

the

into

squalene

that

enhanced

of

diet,

inhibition the

that

glucose

lipogenic

between

clearly

diet. Surprisingly, 14 C-label from

of

from

AND DISCUSSION

by the

squalene the

lanosterol inhibition

and

section

of

is is

conactual

cholesterol.

REFERENCES 1. Dietschy, J.M., and Wilson, J.D. (1970) New Engl.J.Med. 2. Rodwell, V.W., McNamara, D.J., and Shapiro, D.J. (1973) 38: 373-412. 3. Dempsey, M.E. (1974) Ann.Rev.Biochem. -43: 967-990.

352

282:1128-1138. Advan.Enzymol.