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

描述（由申请人提供）：在第三个资助周期的“瘦素运输通过血脑屏障”，我们将集中在瘦素受体（ObR）阳性星形胶质细胞在传递瘦素从血液到中枢神经系统后穿过血脑屏障（BBB）的作用。我们推测，星形胶质细胞不仅调节瘦素运输的重要组成部分的血脑屏障，但也调节神经元瘦素信号，使更快的开始和更快的终止瘦素作用的神经元。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）表达亚型和瘦素周转的影响。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CNS动力学的作用。在目标1中，我们将测试的假设，反应性星形胶质细胞促进周转的瘦素在大脑中，通过加速细胞内降解的瘦素。在目标2中，我们将测试的假设，即反应性星形胶质细胞在文化和成年发病的肥胖症的小鼠表现出不平衡的ObR亚型的差异调节所造成的。目标3将集中在成年小鼠饮食诱导的肥胖或Avy突变，这两种表现出区域特异性增加星形胶质细胞ObR的调节变化。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基因敲除小鼠，我们将证明这些ObR（+）星形胶质细胞在神经元瘦素信号转导的调节中发挥重要作用。这些结果将首次证明ObR（+）星形胶质细胞在连接BBB转运和CNS对瘦素的反应中的功能。对肥胖症中星形胶质细胞增生和星形胶质细胞ObR上调的后果的理解应该能够使星形胶质细胞靶向对抗肥胖受试者中的神经内分泌失调。

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.