Requirement for Glucocorticoids for Adipogenesis in vivo.

描述(申请人提供)：脂肪组织过多和不足都会导致胰岛素抵抗和糖尿病。因此，了解脂肪细胞形成的过程是非常有意义的。我们对这一过程的大部分了解来自30年来对3T3-L1细胞体外分化的分析，当时给予地塞米松(糖皮质激素)、IBMX(提高细胞内cAMP水平)和胰岛素的成脂鸡尾酒。这种鸡尾酒已经被证明可以诱导成脂转录因子，如C/EBPs和PPAR-3。这些转录因子已被证明是小鼠体内脂肪生成所必需的，但在体内脂肪生成过程中诱导它们的线索尚不清楚。有文献证据表明，体内脂肪生成的线索可能不同于体外使用的线索。例如，来自没有脂肪的脂肪萎缩性小鼠的小鼠胚胎成纤维细胞可以分化成富含脂肪的脂肪细胞。不可能评估GR缺失小鼠在脂肪生成中对GR的需求，因为它们在体内脂肪生成之前就在出生时死亡。为了解决这个问题，这项提议将使用小鼠的脂肪干细胞移植。目的1建立脂肪干细胞移植模型，用于体内成脂研究。一系列潜在的成脂干细胞类型(来自具有在形成脂肪细胞时激活荧光素酶的独特性质的小鼠)将被移植到宿主小鼠体内。目的确定体内成脂过程中糖皮质激素的需要量。成脂干细胞将被移植到肾上腺切除或对照宿主小鼠体内。脂肪生成将通过体内生物发光成像进行评估。目的3探讨GR在体内脂肪形成中的作用。GR阴性或GR野生型对照的成脂细胞将被移植到宿主小鼠体内，并通过分子标记和组织学评估它们的成脂潜力。这些目的应该回答糖皮质激素配体和受体是否是体内脂肪形成所必需的问题。

DESCRIPTION (provided by applicant): Both excess adipose tissue and insufficient adipose tissue result in insulin resistance and diabetes. Therefore understanding the processes by which adipocytes form is of great interest. Much of what we have learned of this process has come from 30 years of analysis of 3T3-L1 cells differentiating in vitro when given an adipogenic cocktail of dexamethasone (glucocorticoid), IBMX (raises intracellular cAMP levels) and insulin. This cocktail has been shown to induce adipogenic transcription factors such as C/EBPs and PPAR-3. These transcription factors have been shown to be required for adipogenesis in vivo in mice, but the cues that induce them in vivo during adipogenesis are unknown. There is evidence from the literature to suggest that the cues for adipogenesis in vivo may differ from those used in vitro. For example, mouse embryonic fibroblasts from lipoatrophic mice with no fat differentiate competently into lipid-laden adipocytes. It is not possible to assess the requirement for GR in adipogenesis in GR-null mice because they die at birth prior to adipogenesis in vivo. To address this problem this proposal will use transplantation of adipose stem cells in mice. Aim 1 To establish a model of adipose stem cell transplantation to study adipogenesis in vivo. An array of potential adipogenic stem cell types (from mice with the unique property of activating luciferase upon forming adipocytes) will be transplanted into host mice. Aim 2 To determine the requirement for glucocorticoids in adipogenesis in vivo. Adipogenic stem cells will be transplanted into adrenalectomized or control host mice. Adipogenesis will be assessed by bioluminescent in vivo imaging. Aim 3 To determine the role of GR in adipogenesis in vivo. Adipogenic cells that are GR-null or GR-wildtype control will be transplanted into host mice and their potential to undergo adipogenesis assessed by molecular markers and histology. These Aims should answer the question as to whether glucocorticoid ligand and receptor are required for adipogenesis in vivo.