Leptin Transport Across the BBB: The Role of ObR (+) Astrocytes

描述（由申请人提供）：在“瘦素跨BBB转运”的第三个资助周期中，我们将重点研究瘦素受体（ObR）阳性星形胶质细胞在穿过血脑屏障（BBB）后将瘦素从血液传递到中枢神经系统中的作用。我们假设星形胶质细胞不仅调节瘦素转运作为血脑屏障的重要组成部分，而且还通过使神经元中瘦素作用更快开始和更快终止来调节神经元瘦素信号传导。对小鼠原代星形胶质细胞的细胞研究将确定反应性星形胶质细胞增生对瘦素受体 (ObR) 表达和瘦素周转亚型的影响。小鼠研究将测试星形胶质细胞活性和星形胶质细胞 ObR 对瘦素分布、细胞信号传导和肥胖发展的中枢神经系统动力学的作用。在目标 1 中，我们将检验以下假设：反应性星形胶质细胞通过加速瘦素的细胞内降解来促进大脑中瘦素的周转。在目标 2 中，我们将检验以下假设：培养物和成年肥胖小鼠中的反应性星形胶质细胞均表现出因差异调节而导致的 ObR 亚型不平衡。目标 3 将重点关注饮食引起的肥胖或 Avy 突变的成年小鼠的调节变化，这两种小鼠都表现出星形胶质细胞 ObR 的区域特异性增加。通过使用神经胶质代谢抑制剂和新产生的星形胶质细胞特异性ObR敲除小鼠，我们将证明这些ObR( )星形胶质细胞在神经元瘦素信号传导的调节中发挥重要作用。该结果将为 ObR( ) 星形胶质细胞将 BBB 运输与 CNS 对瘦素的反应联系起来的功能提供第一个证据。了解肥胖中星形胶质细胞增生和星形胶质细胞 ObR 上调的后果，应该能够靶向星形胶质细胞来抵消肥胖受试者的神经内分泌失调。

DESCRIPTION (provided by applicant): In the third grant cycle of "leptin transport across the BBB", we will focus on the role of leptin receptor (ObR)-positive astrocytes in relaying leptin from blood to the CNS after crossing the blood-brain barrier (BBB). We hypothesize that astrocytes not only regulate leptin transport as vital components of the BBB, but also modulate neuronal leptin signaling by enabling a more rapid onset and faster termination of leptin action in neurons. The cellular studies with primary astrocytes from mice will determine the effects of reactive astrogliosis on subtypes of leptin receptor (ObR) expression and leptin turnover. The mouse studies will test the role of astrocytic activity and astrocytic ObR on CNS kinetics of leptin distribution, cellular signaling, and development of obesity. In Aim 1, we will test the hypothesis that reactive astrocytes facilitate the turnover of leptin in the brain by accelerating intracellular degradation of leptin. In Aim 2, we will test the hypothesis that reactive astrocytes both in culture and in mice with adult-onset obesity show an imbalance of ObR subtypes resulting from differential regulation. Aim 3 will focus on regulatory changes in adult mice with diet-induced obesity or the Avy mutation, both of which exhibit regional specific increases of astrocytic ObR. By use of glial metabolic inhibitors and newly generated astrocyte-specific ObR knockout mice, we will show that these ObR(+) astrocytes play an essential role in the regulation of neuronal leptin signaling. The results will provide the first evidence of the functions of ObR(+) astrocytes in linking BBB transport to the CNS response to leptin. An understanding of the consequence of astrogliosis and upregulation of astrocytic ObR in obesity should enable the targeting of astrocytes to counteract the neuroendocrine dysregulation in obese subjects.