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 10(-9) 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-gamma, 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.
MeSH terms
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Adipose Tissue, Brown / metabolism*
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Adipose Tissue, Brown / pathology
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Aldosterone / pharmacology
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Animals
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Carrier Proteins / genetics
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Carrier Proteins / metabolism
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Cell Differentiation / drug effects
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Cell Differentiation / physiology*
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Dose-Response Relationship, Drug
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Fatty Acid-Binding Protein 7
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Fatty Acid-Binding Proteins
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Hormone Antagonists / pharmacology
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Lipoma / metabolism
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Lipoma / pathology
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Lipoma / ultrastructure
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Lipoprotein Lipase / genetics
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Lipoprotein Lipase / metabolism
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Mice
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Mifepristone / pharmacology
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Mineralocorticoid Receptor Antagonists / pharmacology
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Myelin P2 Protein / genetics
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Myelin P2 Protein / metabolism
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Neoplasm Proteins*
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Nerve Tissue Proteins*
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RNA, Messenger / biosynthesis
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Receptors, Cytoplasmic and Nuclear / genetics
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Receptors, Cytoplasmic and Nuclear / metabolism
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Receptors, Mineralocorticoid / metabolism*
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Spironolactone / analogs & derivatives*
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Spironolactone / pharmacology
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Transcription Factors / genetics
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Transcription Factors / metabolism
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Transcription, Genetic / drug effects
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Triglycerides / metabolism
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Tumor Cells, Cultured
Substances
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Carrier Proteins
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Fabp5 protein, mouse
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Fabp7 protein, mouse
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Fatty Acid-Binding Protein 7
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Fatty Acid-Binding Proteins
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Hormone Antagonists
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Mineralocorticoid Receptor Antagonists
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Myelin P2 Protein
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Neoplasm Proteins
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Nerve Tissue Proteins
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RNA, Messenger
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Receptors, Cytoplasmic and Nuclear
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Receptors, Mineralocorticoid
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Transcription Factors
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Triglycerides
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Spironolactone
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Mifepristone
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Aldosterone
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7-propyl spirolactone
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Lipoprotein Lipase