Institut National de la Santé et de la Recherche Médicale U 478, Faculté de Médecine Xavier Bichat, 75870 Paris, France
![]() |
ABSTRACT |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
By use of
targeted oncogenesis, a brown adipocyte cell line was derived from a
hibernoma of a transgenic mouse carrying the proximal promoter of the
human mineralocorticoid receptor (MR) linked to the SV40 large T
antigen. T37i cells remain capable of differentiating into brown
adipocytes upon insulin and triiodothyronine treatment as judged by
their ability to express uncoupling protein 1 and maintain MR
expression. Aldosterone treatment of undifferentiated cells induced
accumulation of intracytoplasmic lipid droplets and mitochondria. This
effect was accompanied by a significant and dose-dependent increase in
intracellular triglyceride content (half-maximally effective dose
109 M) and involved MR, because it was unaffected by
RU-38486 treatment but was totally abolished in the presence of
aldosterone antagonists (spironolactone, RU-26752). The expression of
early adipogenic gene markers, such as lipoprotein lipase, peroxisome
proliferator-activated receptor-
, and adipocyte-specific fatty acid
binding protein 2, was enhanced by aldosterone, confirming activation
of the differentiation process. We demonstrate that, in the T37i cell
line, aldosterone participates in the very early induction of brown
adipocyte differentiation. Our findings may have a broader biological
significance and suggest that MR is not only implicated in maintaining
electrolyte homeostasis but could also play a role in metabolism and
energy balance.
uncoupling proteins; peroxisome proliferator-activated receptor-
![]() |
INTRODUCTION |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
ALDOSTERONE, THE MAJOR MINERALOCORTICOID hormone, is involved in the control of water and sodium homeostasis and participates in the regulation of blood pressure. It is known that aldosterone exerts its biological effects through its binding to the mineralocorticoid receptor (MR) present in sodium-transporting epithelia, such as the distal renal tubules, distal colon, and sweat and salivary glands (2). More recently, MR expression has been extended to a large variety of tissues, including nonepithelial cells of the central nervous system, the cardiovascular system, and also mononuclear leukocytes, skin, and lung (36), in which specific aldosterone effects have been described (5, 8, 30).
We have recently shown that expression of the human MR (hMR) is under
the control of two alternative promoters, P1 and P2, located upstream
of the two first untranslated exons 1 and 1
of the hMR gene,
respectively. In vitro studies have demonstrated that these two
promoters differ strikingly by their basal transcriptional activity as
well as their corticosteroid regulation (34). In an
attempt to further characterize hMR promoter functions in vivo, we have
established transgenic mice in which the proximal P1 and the distal P2
regions were used to direct expression of the SV40 large T antigen
(35). This targeted oncogenesis strategy revealed important functional differences between these promoters, not only in
terms of differential tissue-specific utilization but also with regard
to their relative potency. Indeed, P1 is a strong promoter, active in
all MR-expressing cells, whereas the P2 promoter is approximately ten
times less potent, and its activity is restricted to a limited number
of tissues. Interestingly, the phenotypic presentation of transgenic
animals allowed identification of new sites of MR expression. The
P1-TAg founder animals presented with malignant hibernomas originating
from brown fat, indicating that the P1 promoter was transcriptionally
active in brown adipose tissue (BAT). We subsequently demonstrated that
endogenous MR was constitutively expressed in this tissue, suggesting
that BAT was a previously unrecognized mineralocorticoid target
(35).
Brown fat is a highly specialized tissue involved in thermoregulation
in rodents (19) and has been shown to participate in
energy balance and body weight control in humans (4).
Brown adipocytes are the site of adaptive thermogenesis, because they increase energy expenditure and dissipate energy as heat. This results
from the action of the BAT-specific protein uncoupling protein 1 (UCP1), which functions as a mitochondrial proton translocator, uncoupling oxidative phosphorylation and shutting down ATP synthase activity, the last enzymatic step of the respiratory chain
(23). To determine whether mineralocorticoids could play a
role in BAT function, we studied their effects on the T37i cell line,
derived from one hibernoma of a P1-TAg transgenic mouse. T37i cells
maintain the ability to undergo terminal differentiation and remain
capable of expressing UCP1 upon retinoic acid and -adrenergic
stimulation (35). More importantly, T37i cells express
endogenous mouse MR at both mRNA and protein levels, thus constituting
an ideal model to investigate aldosterone effects on brown adipocyte
proliferation and differentiation. In this report, we show that
aldosterone, through its interaction with MR, promotes T37i cell
differentiation into mature brown adipocytes, as judged by
morphological changes, increased triglyceride accumulation, and
induction of early adipogenic gene expression. These results implicate
another member of the nuclear receptor superfamily in the complex brown
adipocyte differentiation process and further suggest that MR
participates not only in hydroelectrolytic homeostasis but also in the
regulation of energy balance.
![]() |
MATERIALS AND METHODS |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
Cell culture.
The T37i cell line was derived from a hibernoma (malignant brown fat
tumor) of the transgenic mouse founder 37 carrying a hybrid gene
composed of the human MR proximal promoter linked to the SV40 large T
antigen (35). T37i cells were cultured in DMEM-Ham's F12
medium (GIBCO BRL) supplemented with 10% FCS (normal or treated with
dextran-coated charcoal), 2 mM glutamine, 100 IU/ml penicillin, 100 µg/ml streptomycin, and 20 mM HEPES, and were grown at 37°C in a
humidified atmosphere with 5% CO2. Differentiation into
adipocytes was achieved under standard conditions by incubating subconfluent undifferentiated T37i cells with 2 nM triiodothyronine (T3; Sigma Chemical, St Louis, MO) and 20 nM insulin (GIBCO
BRL) for 3 days. Thiazolidinedione (BRL-49653) was a generous gift of
Dr. R. Negrel (Sophia Antipolis, France). The differentiation process
was studied under different experimental conditions. Cells were
generally incubated for various periods of time in medium supplemented
with charcoal-treated serum together with different aldosterone or
glucocorticoid concentrations, in the presence or absence of specific
mineralocorticoid (spironolactone or RU-26752) or glucocorticoid
(RU-38486) antagonists kindly provided by Roussel-Uclaf (Romainville,
France). The mitochondrial UCP1 expression was induced by adding 1 µM
isoproterenol (Sigma) for 6 h and then was analyzed by Northern
blot. All of the experiments were performed with T37i cells
between passages 10 and 20.
Cytological and electron-microscopic analyses.
Cells were rinsed twice with PBS, incubated for 15 min at room
temperature with a 0.3% solution of Oil Red 4 (Merck) in
isopropanol-distilled water (60:40, vol/vol). Cells were then rinsed
with distilled water, counterstained with hematoxylin for 3 min,
rinsed, and mounted. For transmission electron microscopy, cells were
grown on transwell filters (Costar) for 7 days in the presence of 10 nM
aldosterone. Cells were rinsed with PBS and then fixed for 30 min with
2.5% glutaraldehyde in PBS at room temperature. Cells were rinsed in
PBS, postfixed with 1% osmic acid for 15 min, dehydrated in graded
ethanol, and embedded in EPON 812 (Fluka, St Quentin, France).
Ultrathin sections were realized on transversely oriented confluent
cells and examined with a Philips EM 410 electron microscope.
Cell growth studies. Cell growth was estimated by measuring DNA synthesis in the T37i cells by incorporation of [3H]thymidine (925 GBq/mmol, Amersham). The cells were seeded in 12-well plates at a density of 104 cells per well in a medium containing 10% charcoal-treated serum supplemented or not with aldosterone. Two days later, cells were incubated with 0.5 µCi tritiated thymidine/well for 6 h. At the end of the incubation, cells were rinsed three times with cold PBS and lysed in 1 ml of 5% trichloroacetic acid for 30 min at 4°C followed by incubation with 1 ml 0.3 N NaOH overnight at 4°C. After neutralization by addition of 5 µl of 1 N acetic acid, the incorporated radioactivity was counted. Results are expressed by incorporated dpm corrected by the number of cells.
Triglyceride measurements. Undifferentiated T37i cells were plated in 12-well plates at a density of 5 × 104 cells/well and grown for 7 days in medium prepared with stripped FCS in the presence or absence of hormones. Cells were rinsed twice with cold PBS, harvested in a total volume of 250 µl of PBS with a rubber policeman, and counted. Cells were subsequently disrupted by sonication (2 × 10 s), and the homogenates were centrifuged for 10 min at 12,000 rpm at 4°C. Protein concentration of the supernatant was determined by the Bradford technique (3). Triglyceride content was measured using a colorimetric determination kit (Procedure 336, Sigma).
RNA analyses.
Total RNA was isolated from undifferentiated or differentiated T37i
cells by use of TRIzol (GIBCO BRL/Life Technologies) reagent extraction
according to the manufacturer's recommendations. Fifteen micrograms of
total RNA were analyzed by Northern blotting performed by standard
techniques. -32P-labeled probes were synthesized by
random priming (Rediprime II random prime labeling system, Amersham
Pharmacia Biotech, Buckinghamshire, UK) with cDNA for mouse lipoprotein
lipase (LPL; 1.43 kb, from Dr. M. C. Schotz, UCLA), mouse
adipocyte-specific fatty acid binding protein 2 (aP2; 0.6 kb, from Dr.
B. Spiegelman, Harvard), mouse peroxisome proliferator-activated
receptors-
2 (PPAR
2; 0.85 kb, from Dr.
E. Z. Amri, INSERM U470, Nice, France), rat UCP1 (from Dr. D. Ricquier, CEREMOD, Meudon, France), and rat
glyceraldehyde-3-phosphate dehydrogenase (GADPH; 0.84 kb, from Dr. B. Escoubet, INSERM U426, Paris, France). Serial hybridizations with
different probes were performed. Specific hybridization signals were
quantified by measuring radioactivity with a Packard Instant Imager.
Membranes were then subjected to autoradiography.
![]() |
RESULTS |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
Aldosterone induces accumulation of triglycerides in T37i cells.
Under standard culture conditions, T37i cells grow as undifferentiated
cells with a fibroblast-like appearance and a unique nucleus (Fig.
1A). In contrast, after
insulin and T3 treatment for 7 days, drastic morphological
modifications were observed; cells became larger and spherical,
accumulating multiple lipid droplets of various sizes as revealed by
the Oil-Red-O staining (Fig. 1C). Similar results were
obtained by incubation with thiazolidinedione (not shown). These
morphological changes were consistent with cells entering into the
adipocyte differentiation program. Note that the majority of
differentiated cells presented with multiple nuclei. The degree of
morphologically recognizable differentiation was almost 100% in the
T37i cells. We tested the influence of aldosterone treatment on
undifferentiated cells. As shown in Fig. 1B, 10 nM
aldosterone induced the appearance of small intracytoplasmic lipidic
vacuoles. This was a strong morphological indication that aldosterone
may participate in the adipocyte differentiation process. Compared with
undifferentiated cells (Fig.
2A), electron-microscopic examination of aldosterone-treated T37i cells (Fig.
2B) confirmed the presence of multiple lipid droplets, which
never did coalesce, and a multilocular aspect, highly characteristic of
brown adipocytes. Differentiated cells also presented numerous
mitochondria, variable in size, bordering the fat vacuoles, a
finding consistent with the high metabolic activity of brown
adipocytes. Interestingly, we could also observe numerous mitochondrial
cristae junctions in the differentiated T37i cells (Fig.
2C). Note that one cell clearly contained two distinctly
visible nuclei, most probably due to the differentiated as well as
neoplastic feature of T37i cells.
|
|
|
|
Aldosterone stimulates specific gene transcription in T37i cells.
We first analyzed the temporal pattern of expression of known
adipogenic regulators during adipocyte differentiation of T37i cells.
Northern blot analysis was performed with total RNA samples from
control or treated cells isolated daily at different times postconfluence. We examined the levels of mRNA for LPL, aP2, and PPAR, all genes known to be sequentially activated in a
differentiation-specific manner, at least in most white adipocyte
models (3T3-F24A, and the like) (18). GAPDH was used as an
internal control. Figure 5 illustrates
the sequential gene activation observed during differentiation induced
by insulin and T3 treatment. LPL expression rapidly
increased within the first 48 h and reached a maximum at day
6 to progressively decrease afterward. Similarly, exposure to
insulin and T3 stimulated PPAR
expression as early as
day 2, reaching the maximum levels of PPAR
2
mRNA expression by day 6 and remaining unchanged thereafter. In constrast, aP2 was progressively expressed during this
differentiation process, reaching a maximum expression at day
8. This coincided with the full expression of adipogenic genes. It
has to be noted that T37i cells cultured for long periods of time (up
to 15 days), even in the presence of charcoal-dextran-treated serum,
could undergo a spontaneous differentiation process, as evidenced by the appearance of morphological changes and expression of substantial amounts of adipose-specific genes (not shown).
|
|
|
![]() |
DISCUSSION |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
In the present article, we provide evidence of a role for aldosterone via the MR in the differentiation process of T37i cells into mature brown adipocytes. Up to now, aldosterone effects were considered to be restricted mainly to the control of sodium and water homeostasis through its interaction with the MR present in sodium-transporting epithelia of the distal nephron, colon, and the sweat and salivary glands. Strong lines of evidence indicate that aldosterone also exerts specific effects on nonepithelial cells of the central nervous and cardiovascular systems (5, 8), although the molecular basis of aldosterone action and the mineralocorticoid selectivity-conferring mechanisms remain elusive. More recently, using a targeted oncogenesis strategy in transgenic mice, we have identified brown adipose tissue as a novel mineralocorticoid target (35). The newly established T37i cell line was further examined in an attempt to characterize aldosterone's effects in this tissue. It is important to note that studies of the effects of aldosterone on cell lines have been hampered by the fact that most of them (primary cultures as well as immortalized cell lines) lose expression of MR. Our targeted oncogenesis strategy allowed us to circumvent this problem by placing the immortalizing oncogene, at least in part, under the same regulatory sequences as the endogenous MR.
We have now shown that aldosterone exposure at nanomolar concentrations
was able to promote the conversion of T37i cells into fully
differentiated brown adipocytes. Upon aldosterone treatment, major
morphological changes were observed with the appearance of an adipocyte
phenotype, associating multiple intracytoplasmic lipid vacuoles with an
increase in the number and size of mitochondria. Interestingly, because
it is known that brown adipocyte mitochondria architecture presents
specific features such as crista junctions (21), the T37i
cell could represent an ideal model for investigating inner
mitochondrial membrane topology in relation to the metabolic and
bioenergetic status of the cell. Differentiation-associated morphological changes correlated with biochemical modifications consisting of a twofold increase in triglyceride contents.
Time-dependent variations in expression of adipogenic genes such as
LPL, PPAR2, and aP2 were clearly detected in
aldosterone-stimulated cells compared with control. However,
aldosterone was less potent with a delayed time course than insulin and
T3 in inducing PPAR
expression, which may in part
explain the difference in the degree of adipose conversion of T37i
cells between the two treatments. This might be due to the simultaneous
activation of two different signaling pathways in cells treated by
insulin and thyroid hormones, resulting in synergistic effects on
PPAR
expression at both transcriptional and posttranscriptional
levels. More importantly, aldosterone-differentiated T37i cells
maintained the ability to express UCP1 after
-adrenergic stimulation, indicating terminal differentiation and full maturation of
brown adipocytes. Preliminary results indicated that differentiated T37i cells are also able to synthesize and excrete leptin (M. Buyse, S. Viengchareun, A. Bado, and M. Lombès, unpublished results), confirming the major interest of this cellular model in the examination of regulatory mechanisms of leptin secretion and the effects of leptin
on specific adipogenic gene expression and the differentiation process.
Several lines of evidence strongly support the involvement of MR in the differentiation of T37i cells. First of all, the low concentration of aldosterone (1 nM) used to induce triglyceride accumulation (see Fig. 3) was in accordance with the Kd of aldosterone for MR determined in this cellular model (35). In addition, aldosterone effects were still observed in the presence of RU-38486 but were abolished by addition of mineralocorticoid antagonists, which clearly indicates that aldosterone-stimulated differentiation was mediated by the MR.
Glucocorticoids are known to be potent activators of adipogenic
differentiation. In our cellular model, glucocorticoids and mineralocorticoids have overlapping effects on adipocyte
differentiation. Because glucocorticoid hormones bind to MR with
affinities similar to aldosterone, mineralocorticoid selectivity of
aldosterone action in target cells is ensured in part by the
enzyme 11-hydroxysteroid dehydrogenase 2 (11HSD2), which
catalyzes the rapid metabolism of glucocorticoids into inert 11-keto
forms (6). Because we failed to detect in Northern blot
analysis the presence of 11HSD2 transcripts in either normal or
neoplastic BAT and in T37i cells (35), it is possible
that, in this tissue, MR is predominantly occupied by glucocorticoids
and functions as a glucocorticoid receptor. However, preliminary
results performed in T37i cells indicate the presence of a metabolic
conversion of corticosterone into 11-dehydrocorticosterone, suggesting
that some MR-protecting enzymatic mechanisms might be operating in
these cells. It remains to be established whether this activity
corresponds to 11HSD type 2 or to another, as yet unidentified,
tissue-specific isoform. In addition, the circadian fluctuations and
the pulsatile variations of glucocorticoid levels may, in certain
situations, allow aldosterone to access the MR even in the absence of
specificity-conferring mechanisms (5). Finally, because
heterodimerization between members of the nuclear receptor superfamily
is well established, bringing about diverse complexes with specific
transcriptional properties (7), MR could represent an
important dimerization partner for the GR in mediating tissue-specific
effects and even potentiate transcriptional activities, as already
reported in different cellular and promoter contexts (17,
34).
The adipocyte differentiation program is an extremely complex process
in which two major families of transcription factors are required, the
CCAAT/enhancer-binding proteins (C/EBP) and PPAR. During adipogenesis,
a cascade of gene activation for transcription factors and
adipocyte-specific genes occurs in a coordinated and time-dependent
manner (18). In the course of white adipocyte differentiation at least, it has been shown that C/EBP and -
are
induced early and synergistically stimulate the expression of PPAR
and C/EBP
(31). At the final stage of differentiation, expression of adipogenic genes such as LPL, aP2, or GLUT-4 is induced
by PPAR
alone or cooperatively with C/EBP
, which results in
mature adipocyte phenotype (32). In contrast to white
adipocytes, which function mainly as lipid storage, brown adipocytes
have highly specialized thermogenic activity due to the presence of the
mitochondrial UCP1, whose expression is regulated by multiple signaling
pathways including PPAR
, TR, RXR, and
-adrenergic receptors
(23). It has been reported that both
1- and
3-adrenergic receptors are expressed in BAT
(13). We have not yet determined which subtypes are
expressed in T37i cells. The temporal expression pattern of adipogenic
genes in T37i cells reported in Fig. 5 is consistent with the
sequential gene activation described above. The mitochondrial UCP1 is
the last gene expressed during the differentiation process of T37i cells.
Knock-out animal models for C/EBP (29), C/EBP
, and
C/EBP
(26) demonstrate that these transcriptional
factors are essential for brown adipocyte differentiation. However,
C/EBP
and PPAR
are not sufficient for full differentiation
(26). Other factors, such as an estrogen-related receptor
(ERR
) (25, 28) and adipocyte determination
and differentiation-dependent factor 1/sterol regulatory element-binding protein 1 (ADD1/SREBP1) (15), are also
implicated in brown adipocyte differentiation. Recently,
PPAR
-coactivator 1 (PGC-1), a coactivator of PPAR
that is
exclusively expressed in BAT and skeletal muscle (22), has
been clearly identified as a key factor in brown adipocyte
differentiation. It will be of great interest to determine whether
PGC-1 is also expressed in T37i cells. It was shown that PGC-1 binds to
various members of the nuclear receptor superfamily, such as TR and ER,
through an interaction outside the classical activation function 2 (AF2) domain located in the COOH-terminal part of the nuclear
receptors. It may be of interest to determine whether PGC-1 interacts
with and/or modulates the transcriptional activity of MR. Because it has been shown that another coactivator, steroid receptor coactivator 1 (SRC-1), is not expressed in BAT (12), it could be
speculated that specific aldosterone effects on brown adipocytes and
white fat (24) might depend in part on the relative levels
of coactivators such as PGC-1 or SRC-1, respectively.
Our results suggest that aldosterone might play a role in a very early stage of the T37i cell differentiation program between adipoblast and preadipocyte, whereas terminal differentiation of immature to mature adipocytes does not seem to require the presence of MR. MR could regulate specific gene expression at the transcriptional level, but the nature of the primarily aldosterone-induced proteins remains to be determined. Of particular interest is the observation that brown adipocyte differentiation correlates with a decrease in c-jun content (33). Because activating protein 1 (AP-1) activity is modulated by interaction with nuclear receptors, including glucocorticoid receptor (GR) (11, 14, 20), such a mechanism could account for the MR-mediated responses in brown adipocytes. On the other hand, because a role of phosphatidylinositol (PI) 3-kinase has recently been demonstrated in aldosterone regulation of epithelial sodium channels in renal A6 cells (1), MR could also intervene by affecting the PI 3-kinase pathway, whose activation was shown to be an essential requirement for fetal brown adipocyte differentiation (27).
The physiological significance of aldosterone-induced differentiation of brown fat remains to be evaluated. However, an enlargement of the brown adipose tissue surrounding kidneys and adrenal glands has been observed in patients presenting hyperaldosteronism (9). Because emergence of brown adipocyte depots has been reported in white fat of both rodents (10) and humans (4, 16), our findings could be particularly relevant for human physiology, as an important factor determining the capacity to adapt thermogenesis and to mobilize triglyceride storage. Whether brown adipocytes arise from a preadipoblast capable of acquiring brown adipocyte phenotype under stimulation of specific factors, including aldosterone, remains to be determined.
In conclusion, the T37i cell line constitutes an interesting model for examining the regulatory mechanisms of differentiation and specific gene expression in brown adipocytes. Our results clearly demonstrate that MR participates in the differentiation of T37i cells, as evidenced by hormone-induced morphological, biochemical, and molecular modifications, and they indicate that MR is involved in this complex process. In addition to the well-known effect of aldosterone as a determinant factor implicated in sodium homeostasis, we provide first evidence of a role for aldosterone exerting specific functions on brown adipose tissue physiology, which thus constitutes a possible link between electrolyte and energy balance.
![]() |
ACKNOWLEDGEMENTS |
---|
We thank Drs. D. Ricquier and C. Forest (Ceremod, Meudon, France) for helpful discussions; Dr. R. Negrel (Nice, France) for the gift of thiazolidinedione; and Drs. A. Lombès and A. Baker for help in mitochondrial examination. The assistance of J. Grellier, G. Delrue, and P. Disdier in preparation of illustrations, and of Dr. A. Marette for critical reading of the manuscript, is also gratefully acknowledged.
![]() |
FOOTNOTES |
---|
Address for reprint requests and other correspondence: Marc Lombès, INSERM U 478, Faculté de Médecine Xavier Bichat 16, rue Henri Huchard, BP 416, 75870 Paris Cedex 18, France (E-mail: mlombes{at}bichat.inserm.fr).
The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. §1734 solely to indicate this fact.
Received 19 November 1999; accepted in final form 16 March 2000.
![]() |
REFERENCES |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
1.
Blazer-Yost, BL,
Punescu TG,
Helman SI,
Lee KD,
and
Vlahos CJ.
Phosphoinositide 3-kinase is required for aldosterone-regulated sodium reabsorption.
Am J Physiol Cell Physiol
277:
C531-C536,
1999
2.
Bonvalet, JP.
Regulation of sodium transport by steroid hormones.
Kidney Int
53:
S49-S56,
1998.
3.
Bradford, MM.
A rapid and sensitive method for the quantitation of microgram quantities of protein utilizing the principle of protein-dye binding.
Anal Biochem
72:
248-254,
1976[ISI][Medline].
4.
Champigny, O,
and
Ricquier D.
Evidence from in vitro differentiating cells that adrenoceptor agonists can increase uncoupling protein mRNA level in adipocytes of adult humans: an RT-PCR study.
J Lipid Res
37:
1907-1814,
1996[Abstract].
5.
De Kloet, ER,
Vreugdenhil E,
Oitzl MS,
and
Joels M.
Brain corticosteroid receptor balance in health and disease.
Endocr Rev
19:
269-301,
1998
6.
Farman, N.
Molecular and cellular determinants of mineralocorticoid selectivity.
Curr Opin Nephrol Hypertens
8:
45-51,
1999[ISI][Medline].
7.
Forman, BM,
Umesono K,
Chen J,
and
Evans RM.
Unique response pathways are established by allosteric interactions among nuclear hormone receptors.
Cell
81:
541-550,
1995[ISI][Medline].
8.
Funder, JW.
Aldosterone, salt and cardiac fibrosis.
Clin Exp Hypertens
19:
885-899,
1997[ISI][Medline].
9.
Garruti, G,
and
Ricquier D.
Analysis of uncoupling protein and its mRNA in adipose tissue deposits of adult humans.
Int J Obes Relat Metab Disord
16:
383-390,
1992[Medline].
10.
Guerra, C,
Koza RA,
Yamashita H,
Walsh K,
and
Kozak LP.
Emergence of brown adipocytes in white fat in mice is under genetic control. Effects on body weight and adiposity.
J Clin Invest
102:
412-420,
1998
11.
Heck, S,
Kullmann M,
Gast A,
Ponta H,
Rahmsdorf HJ,
Herrlich P,
and
Cato AC.
A distinct modulating domain in glucocorticoid receptor monomers in the repression of activity of the transcription factor AP-1.
Embo J
13:
4087-4095,
1994[Abstract].
12.
Jain, S,
Pulikuri S,
Zhu Y,
Qi C,
Kanwar YS,
Yeldandi AV,
Rao MS,
and
Reddy JK.
Differential expression of the peroxisome proliferator-activated receptor gamma (PPARgamma) and its coactivators steroid receptor coactivator-1 and PPAR-binding protein PBP in the brown fat, urinary bladder, colon, and breast of the mouse.
Am J Pathol
153:
349-354,
1998
13.
Jockers, R,
Issad T,
Zilberfarb V,
de Coppet P,
Marullo S,
and
Strosberg AD.
Desensitization of the beta-adrenergic response in human brown adipocytes.
Endocrinology
139:
2676-2684,
1998
14.
Karin, M,
Liu Z,
and
Zandi E.
AP-1 function and regulation.
Curr Opin Cell Biol
9:
240-246,
1997[ISI][Medline].
15.
Kim, JB,
and
Spiegelman BM.
ADD1:SREBP1 promotes adipocyte differentiation and gene expression linked to fatty acid metabolism.
Gene Dev
10:
1096-1107,
1996[Abstract].
16.
Krief, S,
Lonnqvist F,
Raimbault S,
Baude B,
Van Spronsen A,
Arner P,
Strosberg AD,
Ricquier D,
and
Emorine LJ.
Tissue distribution of beta 3-adrenergic receptor mRNA in man.
J Clin Invest
91:
344-249,
1993[ISI][Medline].
17.
Liu, W,
Wang J,
Sauter NK,
and
Pearce D.
Steroid receptor heterodimerization demonstrated in vitro and in vivo.
Proc Natl Acad Sci USA
92:
12480-12484,
1995[Abstract].
18.
Mandrup, S,
and
Lane MD.
Regulating adipogenesis.
J Biol Chem
272:
5367-5370,
1997
19.
Nicholls, DG,
and
Locke RM.
Thermogenic mechanisms in brown fat.
Physiol Rev
64:
1-64,
1984
20.
Pearce, D,
and
Yamamoto KR.
Mineralocorticoid and glucocorticoid receptor activities distinguished by nonreceptor factors at a composite response element.
Science
259:
1161-1165,
1993[ISI][Medline].
21.
Perkins, GA,
Song JY,
Tarsa L,
Deerinck TJ,
Ellisman MH,
and
Frey TG.
Electron tomography of mitochondria from brown adipocytes reveals crista junctions.
J Bioenerg Biomembr
30:
431-442,
1998[ISI][Medline].
22.
Puigserver, P,
Wu Z,
Park CW,
Graves R,
Wright M,
and
Spiegelman BM.
A cold-inducible coactivator of nuclear receptors linked to adaptive thermogenesis.
Cell
92:
829-839,
1998[ISI][Medline].
23.
Ricquier, D,
and
Bouillaud F.
The mitochondrial uncoupling protein: structural and genetic studies.
Prog Nucleic Acid Res Mol Biol
56:
83-108,
1997[ISI][Medline].
24.
Rondinone, CM,
Rodbard D,
and
Baker ME.
Aldosterone stimulates differentiation of mouse 3T3-L1 cells into adipocytes.
Endocrinology
132:
2421-2426,
1993[Abstract].
25.
Sladek, R,
Bader JA,
and
Giguere V.
The orphan nuclear receptor estrogen-related receptor alpha is a transcriptional regulator of the human medium-chain acyl coenzyme A dehydrogenase gene.
Mol Cell Biol
17:
5400-5409,
1997[Abstract].
26.
Tanaka, T,
Yoshida N,
Kishimoto T,
and
Akira S.
Defective adipocyte differentiation in mice lacking the C/EBP and/or C/EBP
gene.
EMBO J
16:
7432-7443,
1997
27.
Valverde, AM,
Lorenzo M,
Navarro P,
and
Benito M.
Phosphatidylinositol 3-kinase is a requirement for insulin-like growth factor I-induced differentiation, but not for mitogenesis, in fetal brown adipocytes.
Mol Endocrinol
11:
595-607,
1997
28.
Vega, RB,
and
Kelly DP.
A role for estrogen-related receptor alpha in the control of mitochondrial fatty acid beta-oxidation during brown adipocyte differentiation.
J Biol Chem
272:
31693-31699,
1997
29.
Wang, ND,
Finegold MJ,
Bradley A,
Ou CN,
Abdelsayed SV,
Wilde MD,
Taylor LR,
Wilson DR,
and
Darlington GJ.
Impaired energy homeostasis in C/EBP alpha knockout mice.
Science
269:
1108-1112,
1995[ISI][Medline].
30.
Wehling, M,
Kuhnle U,
Weber PC,
and
Armanini D.
Effects of aldosterone on the sodium and potassium concentrations in mononuclear leukocytes from patients with pseudohypoaldosteronism.
Clin Endocr
28:
67-74,
1988[ISI][Medline].
31.
Wu, Z,
Bucher NLR,
and
Farmer SR.
Induction of peroxisome proliferator-activated receptor during conversion of 3T3 fibroblasts into adipocytes is mediated by C/EBP
, C/EBP
, and glucocorticoids.
Mol Cel Biol
16:
4128-4136,
1996[Abstract].
32.
Wu, Z,
Xie Y,
Morrison RF,
Bucher NLR,
and
Farmer SR.
PPAR induces the insulin-dependent glucose transporter GLUT4 in the absence of C/EBP
during the conversion of 3T3 fibroblasts into adipocytes.
J Clin Invest
101:
22-32,
1998
33.
Yubero, P,
Barbera MJ,
Alvarez R,
Vinas O,
Mampel T,
Iglesias R,
Villarroya F,
and
Giralt M.
Dominant negative regulation by c-Jun of transcription of the uncoupling protein-1 gene through a proximal cAMP-regulatory element: a mechanism for repressing basal and norepinephrine-induced expression of the gene before brown adipocyte differentiation.
Mol Endocrinol
12:
1023-1037,
1998
34.
Zennaro, M-C,
Le Menuet D,
and
Lombès M.
Characterization of the human mineralocorticoid receptor gene 5'-regulatory region: evidence for differential hormonal regulation of two alternative promoters via nonclassical mechanisms.
Mol Endocrinol
10:
1549-1560,
1996[Abstract].
35.
Zennaro, MC,
Le Menuet D,
Viengchareun S,
Walker F,
Ricquier D,
and
Lombès M.
Hibernoma development in transgenic mice identifies brown adipose tissue as a novel target of aldosterone action.
J Clin Invest
101:
1254-1260,
1998
36.
Zennaro, MC,
and
Lombès M.
Mineralocorticoid receptor isoforms.
Curr Op Endocrinol Diab
5:
183-188,
1998.