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Glucocorticoid Receptor Signaling Is Not Required for In Vivo Adipogenesis.

ABSTRACT: Regulation of adipogenesis is of major interest given that adipose tissue expansion and dysfunction are central to metabolic syndrome. Glucocorticoids (GCs) are important for adipogenesis in vitro. However, establishing a role for GCs in adipogenesis in vivo has been difficult. GC receptor (GR)?null mice die at birth, a time at which wild-type (WT) mice do not have fully developed white adipose depots. We conducted several studies aimed at defining the role of GC signaling in adipogenesis in vitro and in vivo. First, we showed that GR-null mouse embryonic fibroblasts (MEFs) have compromised ability to form adipocytes in vitro, a phenotype that can be partially rescued with a peroxisome proliferator-activated receptor ? agonist. Next, we demonstrated that MEFs are capable of forming de novo fat pads in mice despite the absence of GR or circulating GCs [by bilateral adrenalectomy (ADX)]. However, ADX and GR-null fat pads and their associated adipocyte areas were smaller than those in controls. Second, using adipocyte-specific luciferase reporter mice, we identified adipocytes in both WT and GR-null embryonic day (E)18 mouse embryos. Lastly, positive perilipin staining in WT and GR-null E18 embryos confirmed the presence of early white inguinal and brown adipocytes. Taken together, these results provide compelling evidence that GCs and GR augment but are not required for the development of functional adipose tissue in vivo.

SUBMITTER: Bauerle KT

PROVIDER: S-EPMC5905394 | biostudies-literature | 2018 May

REPOSITORIES: biostudies-literature

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Glucocorticoid Receptor Signaling Is Not Required for In Vivo Adipogenesis.

Bauerle Kevin T KT Hutson Irina I Scheller Erica L EL Harris Charles A CA

Endocrinology 20180501 5

Regulation of adipogenesis is of major interest given that adipose tissue expansion and dysfunction are central to metabolic syndrome. Glucocorticoids (GCs) are important for adipogenesis in vitro. However, establishing a role for GCs in adipogenesis in vivo has been difficult. GC receptor (GR)‒null mice die at birth, a time at which wild-type (WT) mice do not have fully developed white adipose depots. We conducted several studies aimed at defining the role of GC signaling in adipogenesis in vit ...[more]

PMID: 29579167

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Project description:Differentiation of 3T3-L1 preadipocytes can be induced by a 2-d treatment with a factor "cocktail" (DIM) containing the synthetic glucocorticoid dexamethasone (dex), insulin, the phosphodiesterase inhibitor methylisobutylxanthine (IBMX) and fetal bovine serum (FBS). We temporally uncoupled the activities of the four DIM components and found that treatment with dex for 48 h followed by IBMX treatment for 48 h was sufficient for adipogenesis, whereas treatment with IBMX followed by dex failed to induce significant differentiation. Similar results were obtained with C3H10T1/2 and primary mesenchymal stem cells. The 3T3-L1 adipocytes differentiated by sequential treatment with dex and IBMX displayed insulin sensitivity equivalent to DIM adipocytes, but had lower sensitivity to isoproterenol-stimulated lipolysis and reduced triglyceride content. The nondifferentiating IBMX–then-dex treatment produced transient expression of adipogenic transcriptional regulatory factors C/EBP{beta} and C/EBP{delta}, and little induction of terminal differentiation factors C/EBP{alpha} and PPAR{gamma}. Moreover, the adipogenesis inhibitor preadipocyte factor-1 (Pref-1) was repressed by DIM or by dex-then-IBMX, but not by IBMX-then-dex treatment. We conclude that glucocorticoids drive preadipocytes to a novel intermediate cellular state, the dex-primed preadipocyte, during adipogenesis in cell culture, and that Pref-1 repression may be a cell fate determinant in preadipocytes. We sought to define the genes differentially expressed in response to dexamethasone (dex) in 3T3L1 mouse preadipocytes. We treated 3T3L1 cells with dex or DMSO vehicle for 2 or 36 hrs and then prepared total RNA. We hybridized each sample (Cy5) to a pool of the samples, which served as the reference (Cy3) channel. All linear models for differential gene expression were constructed with the "limma" package (Smyth, 2004) in BioConductor (Gentleman et al., 2004). A linear model for dex was constructed to compare the 4 biological replicates of DMSO vehicle treatment with dex treatment at either 2 or 36hr. Genes were considered differentially expressed if at least one probe had log-odds greater than 50:50 in the linear model.

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Glucocorticoid Receptor Signaling Is Not Required for In Vivo Adipogenesis.

Publications

Glucocorticoid Receptor Signaling Is Not Required for In Vivo Adipogenesis.

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