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Short Communication 1
Segarra AB et al. Dietary Fat and Blood Pressure Control … Horm Metab Res 2008 ; 40: 1 – 3
HMR/473/12.2.2008/Macmillan
received 䊏 䊏 䊏
accepted 䊏 䊏 䊏
Bibliography
DOI 10.1055/s-2008-1046800
Horm Metab Res 2008 ;
40: 1 – 3
© Georg Thieme Verlag KG
Stuttgart · New York
ISSN 0018-5043
Correspondence
M. Ramirez
Unit of Physiology
University of Ja é n
Bldg B-3-263
23071 Ja é n
Spain
Tel.: 䊏 䊏 䊏
Fax: + 34 / 953 / 21 29 43
msanchez@ujaen.es
Dietary Fat Infl uences Testosterone, Cholesterol,
Aminopeptidase A, and Blood Pressure in Male Rats
Authors A . B . S e g a r r a
1
, M . R a m i r e z
1
, I . B a n e g a s
1
, F. A l b a
2
, F. V i v e s
3
, M . d e G a s p a r o
4
, E . O r t e g a
2
, E . R u i z
3
, I. Prieto
1
Affi liations
1
Unit of Physiology, University of Ja é n, Ja é n, Spain
2
Department of Biochemistry and Molecular Biology, University of Granada, Granada, Spain
3
Department of Physiology, University of Granada, Granada, Spain
4
MG Consulting Co., Rossemaison, Switzerland
Introduction
&
A high intake of monounsaturated fat (MUFA)
has been proposed to be a dietary factor able to
decrease the incidence of cardiovascular disease
and hypertension [1] . It has been shown that an
increase in the saturation of dietary fat results in
increased concentrations of total plasma choles-
terol [2] and higher blood pressure [3] . It was
previously shown that serum total cholesterol
levels were higher in mice fed diets containing
saturated oils than in those consuming unsatu-
rated fat. In addition, angiotensin II – degrading
(aminopeptidase A) activity increased progres-
sively with the degree of saturation of dietary
fatty acids [4] . A subsequent study found that
dietary fatty acid composition affected amino-
peptidase A activity in the testes of mice, sug-
gesting a role for fatty acids in male reproductive
functions, including androgen synthesis [5] . It
was recently observed that a diet enriched with
Iberian pig lard remarkably increased serum tes-
tosterone levels in comparison to diets contain-
ing other types of fatty acids with different
degrees of saturation [6] . This and other studies
suggested an infl uence of gonadal steroids and
cholesterol on angiotensin-degrading activities
[7] . Other actions of gonadal steroids by non-
genomic-dependent mechanisms have been
reported, such as stimulation of insulin secretion
and Ca
2 +
uptake as well as vasodilatory effects
[8, 9] . In the present report we analyze the effect
of various diets enriched in fatty acids with dif-
ferent degrees of saturation on systolic blood
pressure, plasma levels of testosterone, total cho-
lesterol, HDL cholesterol, LDL cholesterol, and
angiotensin II – degrading activity.
Materials and Methods
&
Six groups of adult male Wistar rats (200 – 250 g,
n = 8 in each group) were fed with isocaloric diets
for 16 weeks. Each diet was supplemented with
10 % of the oil under investigation: sesame oil,
sunfl ower oil, fi sh oil, olive oil, Iberian pig lard, or
coconut oil. The characteristics of the different
types of dietary fat compared in this study are
summarized in Table 1 [10, 11] .
At the end of the feeding period, systolic blood
pressure in each rat was recorded, and then the
animals were killed by Equithesin anesthesia.
Blood samples were obtained and plasma was
isolated by centrifugation for 10 minutes at
2000 g and stored at − 20 ° C. Plasma testosterone
levels were measured by radioimmunoassay as
previously reported [6] and expressed as nano-
grams per milliliter. Cholesterol levels were
determined colorimetrically with a commercial
kit purchased from Sigma. Aminopeptidase A
activity was determined with a fl uorometric
assay using glutamyl- -naphthylamide as the
substrate, as previously described [12] . Systolic
blood pressure was measured with a tail-cuff
plethysmograph (LE 5001 Pressure Meter, Letica
SA, Barcelona, Spain) in trained, unanesthetized
animals as previously reported [13] . For the sta-
tistical analysis we used one-way analysis of
variance to analyze differences between groups.
Post-hoc comparisons were made with Tukey ’ s
test. P-values below 0.05 were considered signi-
fi cant.
Results and Discussion
&
The results are summarized in 䊉
䉴
F i g . 1 . R a t s f e d
with the fi sh oil or Iberian pig lard diet had sig-
nifi cantly lower blood pressure, plasma total
cholesterol, and LDL cholesterol (p < 0.001) than
animals fed with the other diets. Plasma HDL
Short Communication2
Segarra AB et al. Dietary Fat and Blood Pressure Control … Horm Metab Res 2008 ; 40: 1 – 3
HMR/473/12.2.2008/Macmillan
cholesterol was higher in rats fed the olive oil, Iberian pig lard,
and coconut oil diets but was signifi cantly lower (p < 0.01) in ani-
mals given the sesame oil diet. The sunfl ower and fi sh oil diets
showed a tendency toward lower HDL cholesterol, but the dif-
ferences did not reach statistical signifi cance. Testosterone lev-
els were signifi cantly higher (ranging from two-fold to four-fold)
in animals fed the Iberian pig lard – enriched diet than in rats fed
olive oil (p < 0.001), fi sh oil (p < 0.01), or sesame, sunfl ower, or
Table 1 Fatty acid composition of food fats (grams fatty acid per 100 g total fatty acids)
Fatty acid type Sesame oil [11] Sunfl ower oil [11] Fish oil [11] Olive oil [11] Iberian pig lard [10] Coconut oil [11]
C
8:0
caprylic – – – – – 10.1
C
10:0
capric – – – – – 6.6
C
12:0
lauric – – – – – 45.8
C
14:0
myristic – 0.1 4.5 – 1.2 18.4
C
16:0
palmic 8.9 6.6 0.6 11.8 20.0 8.0
C
16:1
palmitoleic 0.3 0.1 22.1 0.9 2.9 –
C
16:2
hexadecadienoic – – 2.8 – – –
C
17:0
margaric – – 0.8 – – –
C
18:0
stearic 6.0 4.3 6.1 2.8 6.3 2.4
C
18:1
oleic 40.7 22.4 21.7 74.5 59.1 6.0
C
18:2
linoleic 41.7 65.2 2.1 8.7 9.4 1.7
C
18:3
linolenic 1.7 0.3 1.2 1.0 – –
C
18:4
stearidonic – – 0.5 – – –
C
20:0
arachidic 0.8 0.4 – – – –
C
20:1
eicosenoic – – 2.0 – – –
C
20:4
arachidonic – – 3.0 – – –
C
20:5
timnodonic – – 13.2 – – –
C
22:0
behenic – 0.7 – – – –
C
22:5
docosapentaenoic – – 1.5 – – –
C
22:6
clupanodonic – – 17.3 – – –
SAFA 15.7 12 12 13.2 27.6 86.5
MUFA 41 22.4 45.8 73.2 62 5.8
PUFA 43.4 60.7 41.6 8.9 9.4 1.8
SAFA / MUFA 0.38 0.53 0.26 0.18 0.44 14.9
SAFA / PUFA 0.36 0.19 0.28 1.4 2.9 48.0
SAFA = saturated fatty acids; MUFA = monounsaturated fatty acids; PUFA = polyunsaturated fatty acids
0
2
4
6
8
10
12
ng/ml
TESTOSTERONE
*
**
***
0
10
20
30
40
pmol/min/mg prot
AMINOPEPTIDASE A
***
***
0
40
80
120
160
200
mmHg
SYSTOLIC BLOOD PRESSURE
***
***
S
0
40
80
120
160
200
mg/dL
TOTAL CHOLESTEROL
***
***
0
10
20
30
40
50
mg/dL
HDL CHOLESTEROL
**
0
30
60
90
120
150
mg/dL
LDL CHOLESTEROL
***
***
CLOFSF
SCLOFSF
SCLOFSF
SCLOFSF
SCLOFSF
SCLOFSF
Fig. 1 Systolic blood pressure and plasma levels of testosterone, total cholesterol, HDL cholesterol, LDL cholesterol, and aminopeptidase A activity in adult
male Wistar rats fed diets enriched with sesame oil (S), sunfl ower oil (SF), fi sh oil (F), olive oil (O), Iberian pig lard (L), or coconut oil (C). Values are means ±
SEM, n = 8. Total cholesterol was signifi cantly lower in groups F and L than in the other groups. HDL cholesterol was signifi cantly lower in group S than in groups
L and C. LDL cholesterol was signifi cantly lower in group L than in groups S, SF, O, and C and was signifi cantly lower in group F than in group C. Testosterone
concentration was signifi cantly higher in group L than in the other groups. Aminopeptidase A was signifi cantly lower in group S than in groups SF, O, L, and C
and was signifi cantly lower in group F than in group L. Systolic blood pressure was signifi cantly lower in groups L and F than in groups S, SF, O, and C. * p < 0.05,
* * p < 0.01, * * * p < 0.001.
Short Communication 3
Segarra AB et al. Dietary Fat and Blood Pressure Control … Horm Metab Res 2008 ; 40: 1 – 3
HMR/473/12.2.2008/Macmillan
coconut oil (p < 0.05). The diet containing sesame oil signifi cantly
decreased (p < 0.001) aminopeptidase A activity compared with
the other types of dietary fat except for fi sh oil, whereas in ani-
mals fed the latter diet, aminopeptidase A activity was lower
(p < 0.001) than in the Iberian pig lard group. Interestingly, only
rats treated for 16 weeks with the Iberian pig lard diet showed a
marked increased in plasma testosterone levels, which paral-
leled a reduction in total and LDL cholesterol and a decrease in
blood pressure.
To our knowledge, the only comparable study published to date
on the infl uence of fatty acid saturation is a previous report by
Arechaga and colleagues [4] . In this study Balb / C mice were
treated with different diets containing 2.4 g fat per 100 g for 10
weeks. The diet containing pig lard signifi cantly increased total
cholesterol compared with mice fed a diet enriched with sun-
fl ower oil. No difference in aminopeptidase A activity was
observed between the group that consumed pig lard and the
other groups. However, it should be noted that the present study
differed in the experimental model used (rats rather than mice),
the duration of treatment (16 weeks rather than 10 weeks), and
the degree of fat enrichment of the diet (10 g per 100 g food vs.
2.4 g per 100 g). The most important difference is that Iberian pig
lard differs in composition from the pig lard used by Arechaga
and colleagues, which was rich in oleic acid C18:1 (41.1 % ), satu-
rated fatty acids (SAFA; 37.4 % ), monounsaturated fatty acids
(MUFA; 45.9 % ), and polyunsaturated fatty acids (PUFA; 11.3 % )
[4] . In contrast, Iberian pig lard contains a higher percentage of
MUFA + PUFA (62 + 9.5 % ) (mainly oleic C18:1, 59.1 % ) compared
with SAFA (27.6 % ). We therefore propose that the discrepancy
between the two studies is related to the difference in the
unsaturated / saturated fat ratios of the different lard-containing
diets. Indeed, the SAFA / MUFA ratio is 0.44 for Iberian pig lard
and 0.81 for regular pig lard, and the SAFA / PUFA ratio is 2.9 for
Iberian pig lard and 3.4 for regular pig lard. The most remarkable
fi nding is the greater effect of the Iberian pig lard diet on testo-
sterone and lipid levels compared with the effects of other fat-
enriched diets.
The benefi cial effects of testosterone [14] and the deleterious
infl uence of dyslipidemia [15] on cardiovascular function are
well documented. The high levels of aminopeptidase A activity
in animals that consumed the Iberian pig lard – enriched diet
might refl ect the decreased pressor responsiveness to angio-
tensin II caused by increased inactivation of angiotensin II by the
enzyme. Angiotensin II is indeed metabolized to angiotensin III
by aminopeptidase A activity [12] . Moreover, angiotensin II is
considered the main effector peptide of the renin – angiotensin
system, and more than a century of research has documented its
widespread involvement in the pathophysiology of cardiovascu-
lar disease [16] .
However, while both sesame oil and fi sh oil decrease amino-
peptidase A activity, only fi sh oil produces a fall in blood pres-
sure. There is therefore an apparent discrepancy with Iberian pig
lard in that it increases aminopeptidase A activity but also
decreases blood pressure. It should be noted, however, that ses-
ame oil does not improve the lipid profi le. Moreover, there is a
signifi cant decrease in HDL cholesterol for the sesame oil group.
In contrast, both fi sh oil and Iberian pig lard have a clear benefi -
cial effect on lipids. This suggests that aminopeptidase A is not
the only or main factor that infl uences blood pressure. There is
no doubt that lipids have a direct effect on vessel walls and
therefore control their stiffness [17] . The benefi cial effect of fi sh
oil on the lipid profi le may therefore compensate for the
decreased aminopeptidase A activity, which is not the case for
the sesame oil. The lipid profi le, together with the level of testo-
sterone, that results from the type of fat used in the diet may
therefore account (in part) for that discrepancy.
Taken together, the present results suggest that the use of Ibe-
rian pig lard (a type of fat with a low SAFA / MUFA ratio and a
moderately low SAFA / PUFA ratio) in the diet may benefi t cardio-
vascular function in adult male rats. The effect of dietary Iberian
pig lard also should be investigated in female rats to gain a fuller
understanding of the present results, which suggest a benefi cial
role for testosterone.
Acknowledgments
&
This research and work done by A. B. Segarra were supported by
a grant from the University of Ja é n, (ref. UJA2003-015). The
authors thank K. Shashok for improving the use of English in the
manuscript.
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