Metabolic Pathways Involved in the CNS Regulation of Energy Balance

描述(由申请人提供)：近三分之二的美国成年人肥胖或超重(1)，导致每年超过930亿美元的医疗支出(2)。尽管肥胖问题日益严重，但能量平衡的生理调节非常准确，导致卡路里摄入量与卡路里消耗相匹配。这种精确度取决于身体对传递长期和短期能量供应信息的内部信号做出反应的能力。大脑根据营养和激素提示调节能量平衡，而神经元脂肪酸代谢似乎是这一机制的关键。丙二酰辅酶A是脂肪酸合成的基石，当乙酰辅酶A积累时，丙二酸辅酶A含量丰富。多种厌食反应需要丙二酰辅酶A，这表明该分子在下丘脑中作为燃料感知和激素信号之间的纽带发挥作用。然而，丙二酰辅酶A在关键的下丘脑神经元中的关键下游作用尚未确定。这项拨款申请中概述的实验旨在检验中心假设，即丙二酰辅酶A通过刺激哺乳动物下丘脑关键核团中的雷帕霉素靶标(MTOR)来减少食物摄入量。最近，下丘脑mTOR激活被认为是下丘脑燃料传感器的关键(10)。丙二酰辅酶A和mTOR都是C75(5)、瘦素(10)和CNTF(11)显著的厌食作用所必需的。这些底物如何共同作用改变摄食行为尚不清楚，这代表了本提案的一个关键总体目标。具体目的1：证明下丘脑丙二酰辅酶A升高是厌食剂刺激mTOR通路所必需的。具体目的2：验证下丘脑丙二酰辅酶A升高足以引起厌食症和mTOR途径激活的假设。这些假设的测试将包括在乙酰辅酶A羧基酶(ACC)的慢性药物抑制期间的行为和分子分析，乙酰辅酶A羧基酶是产生丙二酰辅酶A所必需的。我们将观察下丘脑丙二酰辅酶A浓缩的效果，通过弓状体内输注腺相关病毒携带针对该基因的短发夹状RNA序列来敲除其降解酶丙二酰辅酶A脱羧酶(MCD)。公共卫生相关性：拟议的研究有望阐明丙二酰辅酶A在调节食物摄入量中的作用，并确定下游目标，将下丘脑丙二酰辅酶A的升高与食物摄入量的减少联系起来。这一贡献意义重大，因为对中枢燃料感应的了解将确定治疗和/或预防肥胖症的新治疗策略。

DESCRIPTION (provided by applicant): Nearly two-thirds of all American adults are obese or overweight (1), resulting in over $93 billion in medical expenditures each year (2). Despite the growing obesity problem, the physiological regulation of energy balance is remarkably accurate resulting in the matching of caloric intake to caloric expenditure (3). This precision is dependent upon the body's ability to respond to internal cues relaying information about both long-term and short-term energy availability. The brain regulates energy balance in response to nutrient and hormonal cues, and neuronal fatty acid metabolism appears to be crucial to this mechanism. Malonyl-CoA is the building block for fatty acid synthesis and is abundant when acetyl-CoA accumulates. Multiple anorectic responses require malonyl-CoA, suggesting a role for the molecule as a nexus between fuel sensing and hormonal signaling in the hypothalamus. However, the key downstream actions of malonyl- CoA in key hypothalamic neurons have yet to be defined. The experiments outlined in this grant application are aimed to test the central hypothesis that malonyl-CoA acts to decrease food intake by stimulating the mammalian Target of Rapamycin (mTOR) in key hypothalamic nuclei. Recently, hypothalamic mTOR activation has been proposed as a critical hypothalamic fuel sensor (10). Both malonyl-CoA and mTOR are required for the dramatic anorectic effects of C75 (5), leptin (10), and CNTF (11). How these substrates might act together to alter ingestive behavior is unknown and represents a key overarching goal of the present proposal. Specific Aim 1: To demonstrate that elevated hypothalamic malonyl-CoA is required for stimulation of the mTOR pathway by anorectic agents. Specfic Aim 2: To test the hypothesis that elevated hypothalamic malonyl-CoA is sufficient to induce anorexia and activation of the mTOR pathway. Tests of these hypotheses will include behavioral and molecular assays during chronic pharmacologic inhibition of acetyl-CoA carboxylase (ACC), which is required for the production of malonyl-CoA. We will observe the effects of hypothalamic malonyl-CoA enrichment, achieved via knockdown of its degrading enzyme, malonyl-CoA decarboxylase (MCD) using intraarcuate infusion of an adeno-associated virus carrying a short hairpin RNA sequence targeted to the gene. PUBLIC HEALTH RELEVANCE: The proposed studies are expected to elucidate the role of malonyl-CoA in the regulation of food intake and to identify downstream targets linking the elevation of hypothalamic malonyl-CoA to the reduction of food intake. This contribution is significant, because an understanding of central fuel sensing will identify novel therapeutic strategies for the treatment and/or prevention of obesity.