Bioscience Reports, Vol. 8, No. 5, 1988
Effect of Noradrenaline Chronic
Administration on Brown Fat Phospholipids
G6rard Mory, ~ Myriam G a w e r 2 and Jean-Claude Kader 2
Received June 27, 1988
Chronic cold exposure of rats (9 days at 5~ induces an alteration of the fatty acid composition of
phospholipids in brown adipose tissue. The alteration is due to an increase of the unsaturation degree
of these lipids. The phenomenon can be reproduced by 10 -7 mole. h - t administration of noradrena~ine for 9 days in rats kept at 25~ Thus, phospholipid alteration in brown fat of cold exposed rats is
most probably a consequence of the increase of sympathetic tone which occurs in this tissue during
exposure to cold.
KEY WORDS: brown adipose tissue; cold-exposure; noradrenaline; phospholipid unsaturation.
INTRODUCTION
In rats there is a good correlation between the level of brown adipose tissue
(BAT) activity and the fatty acid composition of its phospholipids. Exposure of
rats to cold, which triggers the metabolic activation and the redevelopment of this
thermogenic tissue, also induces in BAT a desaturation of phospholipids (review
in: Barnard et al., 1980; Himms-Hagen, 1986). The new fatty acid composition of
BAT total phospholipids (we further refer to the phospholipid "cold pattern" by
contrast with a "control pattern") is characterized by a decrease of the palmitate
(C16:0) content, an increase of arachidonate (C20: 4) content and profound
changes in the respective participation of each C18 fatty acid in phospholipid
composition (H6mon et al., 1974; Senault et al., 1975; Ricquier et al., 1976;
Laury et al., 1984). Similar changes are observed in mitochondrial (Ricquier et
al., 1975) and reticular (Ricquier et al., 1978) phospholipids. The fatty acid
composition of triglycerides is unaffected, or affected in a different way, by
exposure to cold (H6mon et aL, 1974; Senault et al., 1975; Ricquier et al., 1976;
Mory et aI., 1983). It has been observed that BAT from neonate rats is both
highly active and exhibiting a phospholipid composition near to the so-called
~Laboratoire de Physiologie ComparEe ( U R A 307 from CNRS) and 2 Laboratoire de Physiologie
CeUulaire (URA 1180 from CNRS), 4 Place Jussieu, F-75252 Paris Cedex 05, France.
465
0144-8463/g8/1000-0465506.00/09 1988PlenumPublishingCorporation
466
Mory, Gawer and Kader
"cold pattern" (Ricquier and H6mon, 1976). The physiologial function of this
alteration is unknown and it can only be postulated that it modulates the activity
of some metabolic pathways or some transmembrane exchange mechanisms
through changes in membrane fluidity. However, Cannon et al. (1975) found no
significant cold-induced changes in BAT membrane fluidity (but they found no
signifiant changes in the phospholipid composition of BAT either).
The aim of this paper is to determine the role of catecholamines in the
control of this alteration of B A T membrane lipids. When rats are exposed to cold
a sympathetic activation occurs in BAT. Through an increased noradrenaline
release, it triggers heat production, DNA increase, increase in the mitochondrial
concentration of uncoupling protein (UCP), the protein responsible for the
thermogenic activity of BAT, etc. (review in Girardier and Seydoux, 1986;
Himms-Hagen, 1986; Ricquier and Mory, 1984). Thus, noradrenaline seems the
main activator of both BAT metabolic and trophic response to cold exposure. In
a previous study we showed that sympathectomy prevents the appearance of the
cold pattern in the BAT phospholipids when rats are cold-exposed (Mory et al.,
1982), but we could not reproduce this alteration in rats kept at room
temperature by daily catecholamine injection (Mory et al., 1980). The same result
was obtained in the study of UCP control: sympathectomy prevents UCP increase
in cold exposed rats (Mory et al., 1982), while UCP concentration is unaffected
by daily catecholamine administration (Desautels and Himms-Hagen, 1979; Mory
et al., 1980). Finally, we showed that UCP concentration can be increased by
noradrenaline administration, if administration is continuous for several days
(Mory et aL, 1984). Now we have studied phospholipid composition in BAT of
rats, kept at room temperature, treated by noradrenaline delivered continuously
by implanted minipumps in order to ascertain whether such a treatment can
mimick the effect of cold exposure in these lipids.
MATERIALS A N D METHODS
Thirty-nine day-old male rats of the Wistar strain were implanted with an
osmotic minipump A L Z E T T model 2002 and kept at 25~ for 9 days. Pumps,
implanted dorsally upon interscapular BAT, were filled with 0.02M tiron
(Sigma), 0.1 M ascorbic acid and 0.3 M noradrenaline bitartrate and delivered
10 -7 mole/hr noradrenaline. Pumps of control animals contained only the amine
protectors: ascorbic acid and tiron. For comparison, unimplanted rats were
exposed at 5~ for 9 days.
After sacrifice, interscapular BAT was removed, weighed and its lipids
extracted in chloroform according to Folch et al. (1957). Lipid classes were
separated on silica gel plates with hexane/pentane/diethyloxide/glacial acetic
acid 45/45/10/1 vol/vol as solvent (modification of the method of Mangold, 1964).
Lipids were detected by iodine vapour, and phospholipids and triglycerides
scraped off the plates. After saponification of lipids in silica using a
methanol/BF3 mixutre, methylesters of lipids were analyzed by gas-liquidchromatography (GIRDEL apparatus with capillary column) (Kader, 1977).
Noradrenaline and Brown Fat Phospholipids
467
Tissue proteins were extracted by trichloracetic precipitation from the aqueous
phase obtained after lipid extraction and were determined by the biuret method.
RESULTS A N D DISCUSSION
A 9-day exposure of rats to cold induced a large development of BAT and an
increase of BAT protein and phospholipid contents (Table 1). Nine-day chronic
administration of noradrenatine triggers only a small increase in BAT weight,
does not alter phospholipid content of the tissue, but leads to an increase of BAT
protein content as large as that in cold exposed rats. Part of these discrepancies
between cold-exposed and noradrenaline-treated rats could be due to the
dramatic decrease of the lipid load (mainly triglyceride load) observed in BAT of
noradrenaline treated rats (Mory et al., 1984) which should affect BAT weight.
Cold exposure is responsible for a profound alteration in the fatty acid
composition of BAT phospholipids: decrease of the relative part of C 16:0 and
C16:1, increase of the three C18 and C 2 0 : 4 (Figure 1). Noradrenaline
administration induces exactly the same alteration in BAT phospholipids. In the
two situations there is an increase of unsaturation: monounsaturated fatty acids
are weakly affected, but polyunsaturated fatty acids increase significantly, while
saturated fatty acids decrease (Table 1). Neither noradrenaline treatment, nor
exposure to cold, significantly affect fatty acid composition of triglycerides (Fig. 1
and Table 1).
This work is the first demonstration of a modulation of phospholipid
compsition in BAT by noradrenaline. As for the increase of UCP in mitochondria, the "cold pattern" of BAT phospholipids cannot be reproduced by daily
Table 1.
Effect of a 9 day exposure to 5~ or a 9 day chronic administration of
noradrenaline on BAT phospholipids and triglycerides
Body weight (g)
Interscapular BAT (mg)
BAT total proteins (rag)
BAT total phospholipids (rag)
Control
Noradrenalinetreated
Cold-exposed
262 5:8
202 • 14
16.4 • 2.6
2.9 • 0.3
~ 5 • 13 NS
272 • 32 NS
39.7•
2.7•
~ 0 i 12 NS
484 • 44 **
43.8•
6.0•
Fatty acids of phospholipids (% of total phospholipid
Saturated
65.4 • 4.0
Monounsaturated
12.3 • 1.2
Polyunsaturated
22.1 • 3.4
fattyacidmass):
47.4•
~.3•
15.0+0.5NS
15.4•
37.6•
41.5•
Fatty acids of triglycerides (% of total triglyceride fatty acid mass):
Saturated
45.8 • 4.3
41.1 • 1.1 NS
Monounsaturated
33.2 + 1.8
34.4 5:0.8 NS
Polyunsaturated
21.0 • 1.1
24.1 • 0.7 NS
41.7•
34.6•
22.7•
6 cases per determination. Statistics, NS: not significant; *, P - 0 . 0 5 ; **, P_<0.01
(U-test of Mann-Whitney).
Phospholipid concentration was unmodified by eatecholamine treatment on cold
exposure, contrary to that observed during longer exposure to cold (Riequier et al.,
1976; Mory et al., 1982).
Mory, Gawer and Kader
%
0
.
.
.
.
.
.
p
40~x
H
o
5
P
..x
0
L
20.
I
P
I
D
5
CONTROL
%
40_
(-) NA 10-7 mole/h
(9 days)
5"C (9days)
T
R
I
~,
o
~
-;-
G
LY
R
20
2
~o
D
E
5
Fig. 1. Fatty acid patterns of BAT phospholipids and triglycerides. Fatty acids are indicated by their
carbon number, followed by their double bond number; they are expressed as % of the fatty acid total
mass contained in the particular lipid (sum of each pattern is 100%). Dotted lines show control values
of the fatty acid pattern of treated rats; arrows show direction of variation. Number of determinations
is 6. Note that C 14:0 and C 20:3 are only present as traces in phospholipids. The unsaturation index
(carbon-carbon double b o n d s - t o t a l carbon-carbon bonds • 100) is 5.4% for phospholipids from
BAT of control rats, 6.8% for the same lipids in noradrenaline-treated animals and 6.7% in
cold-exposed rats. In a previous work (Mory et aL, 1981) we found 5.5% in BAT of adult control rats
and 7.8% for 5 week cold-exposed animals.
injection of catecholamines. However, as for UCP increase, the alteration of
phospholipids can be reprodued at room temperature by chronic administration
of noradrenaline delivered directly to the tissue. Thus the change, when occurring
in cold-exposed rats, can be considered as a consequence of the increase of
sympathetic tone induced in BAT by cold stimulus.
We can conclude that the present data constitute another example of the
trophic control of BAT by catecholamines which are able to trigger and maintain
almost all the characteristics of the highly thermogenic BAT from cold exposed
animals.
ACKNOWLEDGEMENTS
We thank Christine Blanchard and Daisy Chervin for their expert technical
assistance, as well as Stephane Melik and Benoit W6ssmer for their helpful
participation to this work and Maud Mortassagne for reading the manuscript.
Financial support was provided by CNRS.
Noradrenaline and Brown Fat Phospholipids
469
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