Expression and subcellular localization of estrogen receptors α and β in human fetal brown adipose tissue.
BACKGROUND
Brown adipose tissue (BAT) has the unique ability of generating heat due to the expression of mitochondrial uncoupling protein 1 (UCP1). A recent discovery regarding functional BAT in adult humans has increased interest in the molecular pathways of BAT development and functionality. An important role for estrogen in white adipose tissue was shown, but the possible role of estrogen in human fetal BAT (fBAT) is unclear.


OBJECTIVE
The objective of this study was to determine whether human fBAT expresses estrogen receptor α (ERα) and ERβ. In addition, we examined their localization as well as their correlation with crucial proteins involved in BAT differentiation, proliferation, mitochondriogenesis and thermogenesis including peroxisome proliferator-activated receptor γ (PPARγ), proliferating cell nuclear antigen (PCNA), PPARγ-coactivator-1α (PGC-1α), and UCP1.


METHODS
The fBAT was obtained from 4 human male fetuses aged 15, 17, 20, and 23 weeks gestation. ERα and ERβ expression was assessed using Western blotting, immunohistochemistry, and immunocytochemistry. Possible correlations with PPARγ, PCNA, PGC-1α, and UCP1 were examined by double immunofluorescence.


RESULTS
Both ERα and ERβ were expressed in human fBAT, with ERα being dominant. Unlike ERβ, which was present only in mature brown adipocytes, we detected ERα in mature adipocytes, preadipocytes, mesenchymal and endothelial cells. In addition, double immunofluorescence supported the notion that differentiation in fBAT probably involves ERα. Immunocytochemical analysis revealed mitochondrial localization of both receptors.


CONCLUSIONS
The expression of both ERα and ERβ in human fBAT suggests a role for estrogen in its development, primarily via ERα. In addition, our results indicate that fBAT mitochondria could be targeted by estrogens and pointed out the possible role of both ERs in mitochondriogenesis.
University of Belgrade (K.V., M.M., I.G., A.K.), Faculty of Biology, Center for Electron Microscopy, and Department of Physiology (V.O., A.S., A.J., M.V., B.B., B.K.), Institute for Biological Research "Sinisa Stankovic," University of Belgrade, 11000 Belgrade, Serbia; Department of Genomic Medicine (A.C.), The Methodist Hospital Research Institute, Houston, Texas 77030; Department of Anatomy (B.S.), Faculty of Medicine, University of Novi Sad, 21000 Novi Sad, Serbia; and Department of Endocrinology (E.S.), Institute of Internal Disease, Clinical Center Vojvodina, 21000 Novi Sad, Serbia.
Ksenija
K
Velickovic
Aleksandra
A
Cvoro
Biljana
B
Srdic
Edita
E
Stokic
Milica
M
Markelic
Igor
I
Golic
Vesna
V
Otasevic
Ana
A
Stancic
Aleksandra
A
Jankovic
Milica
M
Vucetic
Biljana
B
Buzadzic
Bato
B
Korac
Aleksandra
A
Korac
D002001:Adipose Tissue, Brown / Q000196:embryology / Q000254:growth & development / Q000378:metabolism*; D047628:Estrogen Receptor alpha / Q000378:metabolism*; D047629:Estrogen Receptor beta / Q000378:metabolism*; D005333:Fetus / Q000378:metabolism*; D005865:Gestational Age; D006801:Humans; D007150:Immunohistochemistry; D007473:Ion Channels / Q000378:metabolism; D008297:Male; D024101:Mitochondrial Proteins / Q000378:metabolism; D047495:PPAR gamma / Q000378:metabolism; D000071248:Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha; D018809:Proliferating Cell Nuclear Antigen / Q000378:metabolism; D014018:Tissue Distribution; D014157:Transcription Factors / Q000378:metabolism; D000071256:Uncoupling Protein 1
C506487:ESR1 protein, human; D047628:Estrogen Receptor alpha; D047629:Estrogen Receptor beta; D007473:Ion Channels; D024101:Mitochondrial Proteins; D047495:PPAR gamma; C486497:PPARGC1A protein, human; D000071248:Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha; D018809:Proliferating Cell Nuclear Antigen; D014157:Transcription Factors; C000604371:UCP1 protein, human; D000071256:Uncoupling Protein 1