Requirement for Glucocorticoids for Adipogenesis in vivo.

描述（由申请人提供）：脂肪组织过剩和脂肪组织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趣的。我们对这一过程的大部分了解来自于30年来对3T3-L1细胞体外分化的分析，这些细胞在给予地塞米松（糖皮质激素）、IBMX（提高细胞内cAMP水平）和胰岛素的合成鸡尾酒后分化。这种混合物已被证明可以诱导成脂转录因子，如C/ ebp和PPAR-3。这些转录因子已被证明是小鼠体内脂肪形成所必需的，但在体内脂肪形成过程中诱导它们的线索尚不清楚。有证据表明，体内脂肪形成的线索可能不同于体外使用的线索。例如，来自无脂肪的脂肪萎缩小鼠的小鼠胚胎成纤维细胞能够分化为富含脂肪的脂肪细胞。不可能评估GR缺失小鼠的脂肪形成对GR的需求，因为它们在体内脂肪形成之前就在出生时死亡。为了解决这一问题，本研究建议将脂肪干细胞移植到小鼠体内。目的1建立脂肪干细胞移植模型，研究体内脂肪形成。一系列潜在的脂肪干细胞类型（来自具有在形成脂肪细胞时激活荧光素酶的独特特性的小鼠）将被移植到宿主小鼠中。目的2确定体内脂肪形成过程中糖皮质激素的需要量。脂肪生成干细胞将被移植到肾上腺切除或对照宿主小鼠中。脂肪形成将通过生物荧光体内成像进行评估。目的3探讨GR在体内脂肪形成中的作用。将GR-null或gr -野生型对照的成脂细胞移植到宿主小鼠体内，并通过分子标记和组织学评估其发生脂肪形成的潜力。这些目的应该回答糖皮质激素配体和受体是否需要体内脂肪形成的问题。

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.