J. Nutr,
Sci.
Vitanzinol,
39, 63-71,
Note
The Effect
of Various
Lipoproteins
Phospholipids
and
Liver
Hypercholesterolemic
Lipids
on Plasma
in
Rats
Toshio IWATA,1Yoshiharu KIMURA,2Kentarou TSUTSUMI,1
Yuji FURUKAWA,2
and Shuichi KIMURA2
1Department of Research and Development, The Rinoru Oil Mills Co., Ltd.,
Minato-ku,Nagoya 455, Japan
2 Laboratory of Nutrition, Department of AppliedBiologicalChemistry,
Faculty of Agriculture,Tohoku University,
Aoba-ku,Sendai 981, Japan
(ReceivedMay 19, 1992)
Summary
Rats were fed a hypercholesterolemic diet (5% lard, 0.5%
cholesterol, and 0.25% sodium cholate) containing 5% of dietary
phospholipid as safflower phospholipid (SAP), soybean phospholipid
(SOP), or egg yolk phospholipid (EGP), or 5% of soybean oil (SO) as a
control for 4 weeks. The concentrations of plasma cholesterol were
significantly higher in rats fed the EGP diet than those of the other diets.
Similarly, the concentrations of chylomicron plus very low density
lipoprotein (VLDL) cholesterol were higher in rats fed the EGP diet. The
phospholipid diets induced a significant increase of high density lipoprotein
(HDL) cholesterol in comparision with the SO diet. The concentrations
of liver cholesterol were significantly lower in rats fed the phospholipid
diets than those of the SO diet. Among phospholipid-fed rats, the SAP
and SOP diets decreased the concentrations of liver cholesterol compared
with the EGP diet. The activity of plasma lecithin-cholesterol acyl
transferase (LCAT) was significantly increased in rats fed the phos
pholipid diets. The phospholipid diets caused an enhanced excretion of
neutral steroids into feces. Among phospholipid-fed rats, the SAP and
SOP diets increased the excretion of fecal neutral steroids compared with
the EGP diet. The fatty acid composition of HDL phospholipid was
slightly reflected by the major dietary fat source. These results suggest
that SAP and SOP inhibit markedly the absorption of dietary cholesterol
in the small intestine of hypercholesterolemic rats and that the effect of
SAP and SOP on plasma cholesterol metabolism may be different from
that of EGP.
Key Words safflower phospholipid, soybean phospholipid, egg yolk
phospholipid, plasma cholesterol, liver cholesterol, lipoprotein cholesterol,
lecithin-cholesterol acyltransferase, fecal neutral steroids, hypercholester
olemia, rats
63
1993
64
T. IWATA
The
effect
extensively
of
dietary
studied
in
cholesterol-lowering
We
recently
of
reported
the
had
diet
various
id (10).
yolk
in
rats
(11,
In
olemic
in rats
we
fed
the
rat
or
egg
and
yolk
to
nonpurified
of
the
in
Table
diet
1.
For
of
soybean
of
lard.
or
egg
oil,
A
as
respective
measured
shown
1.
in
day
2,
pair-fed
in
an
and
Composition
1 Composition
(Asahi
Table
according
weight
were
equal
added
to
libitum-fed
gain
of the basal
to Harper
was
of
the
that
consumed
soybean
measured
before
basal
oil
is
shown
safflower
(Rinoru
diets
Oil
Tokyo)
at
the
of
rats
were
on
the
previous
groups.
on
initiation
diet
as
Co.,
basal
lights
a commercial
phospholipid
groups
Each
with
fed
a week
the
rats,
(Funabashi).
were
Industry
to
steroids
soybean
phospholipid
soybean
Chemical
fecal
oil.
Co.
at least
dietary
phospholipid
amount
ad
of
Tokyo),
phospholipid
paired-mate
every
Co.,
5%
dietary
hypercholester
of
(21-25•Ž)
composition
and
Sprague-Dawley
140g
a
level
how
of
soybean
Farm
for
(PC)
cholesterol
phospholipid,
room
Co.)
The
diet,
Mills
Funabashi
Farm
phospholip
investigate
Male
fed
soybean
excretion
with
diets:
rats
phospholip
serum
safflower
approximately
diets.
in
safflower
liver
and
air-conditioned
Funabashi
Oil
diets
an
experimental
yolk
and
lipids
compared
from
to
plasma
and
the
order
the
safflower
cholesterol
that
over
containing
weighing
purified
food-restricted
corresponding
Table
the
in
F-2,
with
in
liver
Animals
Rats
(Rinoru
Co.)
their
(Type
experiments
phospholipid
Mills
h.
liver
in
been
of
controversial.
phosphatidylcholine
in
and
phospholipid,
housed
20:00
and
has
mechanism
phospholipid,
observed
a reduction
metabolism
obtained
still
metabolism
diets
were
individually
08:00
plasma
therefore,
plasma
methods.
pathogen-free,
was
from
lipid
lipoproteins
the
soybean
we
caused
study,
studied
is
to
cholesterol
hypercholesterolemic
Materials
of
and
However,
containing
present
the
have
phospholipid,
specific
the
affect
rats,
addition
Furthermore,
(PE)
24).
phospholipids
in
in
lipids
(4-9).
phospholipids
phospholipid
phosphatidylethanolamine
serum
rats
elevation
(10).
advantages
Egg
and
dietary
that,
suppressed
hypercholesterolemic
on
(1-3)
action
phospholipid
id
phospholipids
humans
et al.
Food
or
5%
expense
given
day
intake
the
by
was
weekly.
diet.
.
J. Nutr.
Sci.
Vitaminol.
VARIOUS
Table
2.
PHOSPHOLIPIDS
Phospholipid
class
AND
and
fatty
HYPERCHOLESTEROLEMIA
acid
composition
65
of dietary
fats
used
in the
experiments.
SO,
soybean
yolk
phospholipid.
oil; SAP,
Analytical
and
blood
procedures:
was
Plasma
lipoprotein
70P-72,
density
ranges
were
using
KBr
Total
was
For
the
each
to
the
phospholipid;
rats
under
were
fasted
overnight,
ether
anesthesia.
sample
of
of
density
and
by
Hitachi
method
low
EGP,
diethyl
plasma
rotor
VLDL,
lipids
of
(TLC)
acid
origin.
The
spots
eluted,
subjected
1, 1993
in plasma
were
fatty
was
of
to
acid
carried
v/v/v).
phospholipids
methanolysis
lipoprotein
in
extracted
in
(70:30:1,
and
levels
triacylglycerol
determination
39, No.
according
phospholipid
Liver
and
chromatography
Vol.
from
fixed-angle
1.006<d<1.063,
levels
and
(9).
ether/acetic
all
aorta
4•Ž
plus
(g/ml),
feeding
soybean
egg
sequential
ultracentrifuge
Havel
et
al.
lipoproteins
1.063<d<
(13).
The
(LDL)
1.21,
and
respectively,
solution.
triacylglycerol
previously
at
Tokyo)
SOP,
abdominal
RPL42T
chylomicron
d<1.006
28-day
the
isolated
an
Hitachi,
of
cholesterol
cholesterol
from
in
(Model
phospholipid;
After
collected
ultracentrifugation
HDL
safflower
liver
were
and
free
determined
cholesterol,
as
described
in chloroform/methanol=2:1(14).
were
determined
composition
out
by
With
of
using
this
visualized
with
fraction
plasma
as
phospholipid
the
system,
with
BF3/CH3OH
Total
described
solvent
previously
of
system
HDL,
of
phospholipids
iodine
(15)
vapor
for
hexane/diethyl
run
were
gas-liquid
(9).
thin-layer
near
scraped
chromato
the
and
66
T. IWATA
Table
3.
Effect
of dietary
the experimental
SO,
oil,
graphic
of
in
Stokke
-20•Ž
SOP,
(n=8).
are
.
Means
significantly
liver
soybean
in
different
the
weight
in rats
fed
phospholipid;
same
column
[LCAT,
EC
EGP,
not
egg
sharing
a
(p<0.05).
When
of
2.3.1.43]
according
to
the
was
method
2
days
fecal
prior
to
neutral
sacrifice
steroids
and
were
immediately
frozen
performed
as
at
described
Statistical
coupled
the
means.
to
achieve
evaluation
with
The
of
a Duncan's
data
acceptable
level
homogeneity
was
New
of
carried
Multiple
of
out
probability
variance,
the
by
Range
was
data
analysis
Test
for
set
were
at
the
95%.
subjected
to
transformation.
Results.
Weight
gain
significant
Liver
weight
lower
than
that
are
fed
other
diets.
lower
than
not
body
of
EGP
EGP
Lipoprotein
lipoprotein
were
the
the
were
concentrations
the
of
EGP
LDL
SAP
in
Table
among
and
than
of
3,
the
SOP
diets.
in
there
were
various
diets
was
no
groups
.
significantly
in
in
of
Table
4.
did
plus
of
not
VLDL
the
other
rats
with
fed
The
those
total
SO
cholesterol
diets
were
diet
the
were
concentrations
of
the
cholesterol
among
of
of
concentrations
other
diets
in the
different
diets
compared
differ
plasma
those
the
phospholipid
concentrations
cholesterol
experimental
in
phospholipid
than
concentrations
various
triacylglycerol
. Plasma
higher
the
cholesterol
comparison
Plasma
groups
fed
total
concentrations
EGP
cholesterol
those
of rats
increased
significantly
chylomicron
diet
the
concentrations
various
shown
HDL
of
concentrations
fed
and
The
are
shown
gain
concentrations
cholesterol
SOP
diet
of
As
weight
fed
significantly
cholesterol:
increase
of rats
The
among
fractions
significant
the
diets.
4.
free
of
weight:
in
lipid
Table
Plasma
the
other
diet
those
liver
weight)
Plasma
in
different
fed
the
lipids:
shown
the
and
differences
(g/100g
Plasma
rats
the
analysis:
statistically
The
for
of
necessary
rats
a substrate
(16).
(ANOVA)
logarithmic
were
as
(10).
classification
rats
acyltransferase
[3H]cholesterol
collected
Analyses
variance
diets
using
Norum
Statistical
in
phospholipid;
lecithin-cholesterol
were
previously
The
letter
plasma
and
Feces
in
gain and
analyses.
determined
of
safflower
* Mean•}SE
superscript
Activity
of
SAP,
phospholipid.
common
on weight
diets
soybean
yolk
phospholipids
et al.
with
the
.
induced
the
various
significantly
SO
a
diet
groups
higher
.
J. Nutr.
Sci.
Vitaminol.
.
.
VARIOUS
PHOSPHOLIPIDS
AND
HYPERCHOLESTEROLEMIA
67
Table 4. Effect of dietary phospholipids on various lipids and activity of lecithin
cholesterol acyltransferase (LCAT) in plasma of rats fed the experimental diets.
SO,
soybean
yolk
sharing
SAP,
to
5.
superscript
logarithmic
Effect
experimental
safflower
phospholipid;
* Mean•}SE
a common
jected
Table
oil;
phospholipid.
SOP,
(n=8).
letter
are
Means
significantly
soybean
the
phospholipid;
same
EGP,
horizontal
egg
column
different (p<0.05).
**
Data
not
sub
transformation.
of
dietary
and
mean
phospholipids
on
various
lipids
in liver
of rats
fed
the
diets.
Abbreviations
values
are the same
LCAT activity:
As shown in Table
higher when rats were fed the phospholipid
diet.
in
But this activity did not differ among
Liver lipids:
Liver lipid concentrations
diets are shown
in Table
as Table
3.
4, the LCAT activity
was significantly
diets than when rats were fed the SO
the phospholipid
diets.
of rats fed the various
5. The concentrations
of liver
cholesterol
experimental
in rats fed the
phospholipid
diets decreased
markedly
in comparison
with those of the SO diet.
Among
phospholipid-fed
rats, the liver cholesterol
in rats fed the SAP and SOP
diets were significantly
lower than that of the EGP diet. The phospholipid
diets
induced a reduction
in liver total lipid compared
with the SO diet; the SAP diet
indicated
the lowest value. The concentrations
the SO diet were significantly
higher than those
Vol.
39, No.
1, 1993
of liver triacylglycerol
of the other diets.
in rats
fed
68
T . IWATA
Table
rats
6.
Effect
of dietary
fed the experimental
Abbreviations
Table
plasma
7.
and
other
Effect of dietary
high
Abbreviations
density
phospholipids
on excretion
of neutral
steroids
into
feces in
diets.
notations
phospholipids
lipoproteins
and other
et al.
are the same
on fatty
as Table
4.
acid composition
of rats fed the experimental
notations
are the same
as Table
of phospholipid
in
diets.
4.
Fecal lipids: Feces dry weight and excretion of neutral steroids into feces in
rats fed the various experimental diets are shown in Table 6. Feces weight (g/2
days) was similar within the various diets. The phospholipid diets caused an enhanced
excretion of neutral steroids into feces compared with the SO diet. Among
phospholipid-fed rats, the SAP and SOP diets induced a higher excretion of neutral
steroids compared with the EGP diet. Although the increase due to the SAP and
EGP diets of fecal neutral steroids was more prominent in cholesterol than in
coprostanol, the increase due to the SOP diet was more prominent in coprostanol
than in cholesterol.
Fatty acid composition of HDL phospholipid: The fatty acid composition of
HDL phospholipid was slightly, but significantly, modified by the constituent fatty
acid of the dietary phospholipids, as shown in Table 7. Oleic acid increased under
the SOP and EGP diets in comparison with the SO diet; the EGP diet indicated
the highest value. Linoleic acid decreased by the EGP diet, compared with the other
diets. Arachidonic acid increased by the SAP and EGP diets; the EGP diet indicated
the highest value. The EGP diet induced an increase of docosahexaenoic acid in
J. Nutr.
Sci.
Vitaminol.
VARIOUS
PHOSPHOLIPIDS
with
the
other
In
addition
comparison
Discussion.
demonstrated
in
showed
that
excretion
we
feces
rats
fed
the
other
also
liver
SO
diet.
and
the
results.
lecithin
was
that
activation
since
of
the
chain
ratio
of
As
to
observed
reported
of
in
phospholipid
fed
a
diets
inhibit
results
inhibition
steroids
of
The
39, No.
SAP
phospholipid
with
of
diets
the
SO
fecal
on
the
neutral
excretion
the
absorption
rats,
both
suggest
that
dietary
cholesterol
of dietary
SAP
and
with
the
EGP
the
a factor
liver
of
not
In
liver
absorption
and
neutral
diets
diet.
cholesterol
except
in
the
composition
We
of
excretion
of
experiment
and
SOP
in
the
has
small
the
action
intestine
excretion
SAP
and
EGP
may
of
the
intestine.
the
the
A
been
that
increased
with
, we
(10).
suppose
Furthermore,
small
acyl
7 , the
steroids
compared
the
diets
SAP
cholesteroliowering
in
SOP
an
cholesterol
enhanced
of
cholesterol
of
Table
acid
by
SOP
via
measured,
in
previous
(20).
We
HDL
the ‡™6-desaturase
steroids
fecal
the
when
cholesterol
transfer
of
an
high
showed
was
fatty
the
greatly
mature
shown
SAP
caused
plasma
cholesterol.
is the
the
on
the
of
presence
diet
the
in
suppresses
diet.
cholesterol-enriched
decreased
hypercholesterolemic
cholesterol
activity.
compared
significantly
or
whether
LCAT
plasma
increased
HDL
As
the
the
markedly
present
the
LCAT
by
to
itself
to
lecithin
rats
due
of
(18).
the
plasma
of
also
phospholipid
by
altered
be
at
excretion
dietary
neutral
diets
These
Vol.
6,
phospholipid4ed
fecal
not
may
compared
enhanced
effect
Among
Table
steroids
the
similar
clear
HDL
both
was
activity
rise
of
with
SOP
LCAT
formation
cholesterol
supplementation
is not
in
to
was
a result
of
catalyzed
PC
linoleate
Such
a
with
cholesterol
of
involved
the
EGP
a reduction
and
LCAT
induced
increase
The
VLDL
experiment
intimately
,
into
.
plasma
the
diet.
elevation
SAP
we
and
compared
elevation
EGP
present
composition
of
relates
shown
is
reaction
position
of
that
diets
acid
of
that
of
SO
comparision
the
been
steroids
induced
in
the
effect
The
reported
may
diet
suppress
from
enzyme
molecular
sn-2
the
10).
phospholipid
cholesterol
neutral
This
Fatty
It
(8)
not
activity
(9,
the
plus
EGP
has
experiment
neutral
cholesterol
suppressed
that
the
with
cholesterol
could
present
of
plasma
the
diets
the
chylomicron
HDL
different
fed
al.
LCAT.
phospholipid
fecal
of
The
diet.
(19).
HDL
be
phospholipids
EGP
activity
diet
dietary
the
since
SOP
were
rats.
arachidonate
the
diet,
to
principal
from
and
of
In
SAP
Furthermore,
liver
lipids
and
excretion
of
of
,10).
plasma
compared
of
rise
experiment,
ct
diets
(9
(10).
the
However,
a
suggest
Jimenez
SOP
and
EGP
EGP
may
diets
(17).
suppose
or
diet.
results
fed
metabolism
lipids
in
concentrations
as
SAP
the
phospholipid
similar
SOP
the
previous
with
EGP
metabolism
In
compared
concentrations
well
cholesterol,
These
alteration
liver
the
as
69
action
diet
favorable
the
the
Although
cholesterol
for
in
hypocholesterolemic
cholesterol-enriched
SOP,
Similarly,
higher
cholesterol.
when
SAP,
cholesterol
liver
and
increased
diets.
were
the
steroids
the
SOP,
a
a
plasma
significantly
to
given
neutral
HVPERCHOLESTEROLEMIA
diets.
caused
studied
in
diet
SAP
of
have
rats
AND
rats
diet.
be
the
fed
diet.
and
and
1, 1993
SOP
excretion
diets
of
caused
fecal
neutral
a
favorable
steroids,
alteration
compared
in
plasma
with
the
and
liver
EGP
diet.
a
70
T. IWATA
et al .
The factor of these different results among phospholipid-fed rats cannot be explained
in the present experiment. The fatty acid composition of EGP is different from that
of SAP and SOP. Although EGP is comprised of 64% of PC and 23% of PE, SAP
and SOP contain several classes of phospholipid. It has been reported that PE
contained in EGP was responsible for the hypocholesterolemic action (11, 21). More
precisely, the constituent base, ethanolamine, was responsible for lowering of the
plasma cholesterol. The major constituent in dietary phospholipids, PC, appeared
to be less effective (11, 21). Other investigators indicated that the inositol moiety of
phosphatidylinositol (PI) may have a significant role in the regulation of lipid
metabolism (22). However, it is not clear in the present experiment whether or not
the respective phospholipids influence the hypocholesterolemic action in
hypercholesterolemic rats. This is worthy of further investigation.
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Sci.
Vitaminol,
VARIOUS
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13)
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17)
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Vol.
PHOSPHOLIPIDS
AND
HYPERCHOLESTEROLEMIA
71
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39, No.
1, 1993