Role of Peroxisome Proliferation in Leptin Resistance

描述(由申请人提供)：为了了解代谢紊乱的病因，包括肥胖和II型糖尿病，我们必须更好地了解如何存储 而可用的能源由中枢神经系统监测。特别是，对细微的细胞相互作用和细胞内机制的理解仍然是难以理解的，这些机制使得下丘脑以及随后对循环激素和营养信号的内分泌和行为反应都是适当的。最近的数据，包括我们实验室的数据(Andrews等人，2008；Benani等人，2007；Anderson等人，2009；Jaillard等人，2009；Campanucci等人，2010；Diano等人，2011)提出了这样的概念，即ROS的产生不仅是底物氧化的副产品，而且在调节参与能量代谢调节的细胞反应中发挥关键作用。我们观察到，抑制ROS水平降低了前阿片黑素皮质素(POMC)细胞的激活，促进了神经肽Y(NPY)/刺鼠相关肽(AgRP)神经元的活动和摄食，而ROS激活了POMC神经元，减少了摄食。我们发现，在瘦肉和肥胖/肥胖动物中，POMC神经元中的ROS水平与瘦素水平呈正相关，这种关系在饮食诱导肥胖(DIO)小鼠中会减弱。此外，高脂喂养可导致下丘脑过氧化体的增殖和PPAR基因表达水平的升高。PPAR激动剂罗格列酮对POMC神经元的过氧化酶体增殖可降低ROS水平，增加高脂饮食瘦小鼠的摄食量。另一方面，PPAR拮抗剂GW9662抑制下丘脑过氧化物酶体的增殖，增加POMC神经元ROS和c-fos的表达，逆转高脂喂养引起的NPY/AgRP升高和POMC神经元放电减少，导致DIO小鼠摄食减少。有趣的是，单独中枢给予ROS增加了POMC神经元中c-fos和pStat3的表达，并减少了对DIO动物的摄食。综上所述，这些观察结果支持了这一应用的中心假设，即在下丘脑瘦素靶向神经元中，PPAR控制的过氧化物酶体增殖与细胞瘦素抵抗有关。为了验证我们的假设，我们提出了以下具体目标：特异的目的1，以确定选择性地消融AgRP或POMC神经元中的瘦素受体对高脂饮食诱导的过氧酶体增殖和下丘脑神经元活动受损的影响。目的探讨选择性损毁POMC、AgRP和Leptin受体表达神经元中PPARγ对标准饲料和高脂饮食小鼠下丘脑环路活动和代谢表型发育的影响。了解下丘脑亚细胞机制是细胞和行为对代谢变化做出反应的基础，这将增强开发更好的战略来对抗代谢紊乱的潜力，包括肥胖和糖尿病。

DESCRIPTION (provided by applicant): To understand the etiology of metabolic disorders, including obesity and type II diabetes, it is essential that we gain better insight into how stored and available energy sources are monitored by the central nervous system. In particular, a comprehension of the fine cellular interplay and intracellular mechanisms that enable appropriate hypothalamic and consequent endocrine and behavioral responses to both circulating hormonal and nutrient signals remains elusive. Recent data, including those from our laboratories (Andrews et al., 2008; Benani et al., 2007; Anderson et al., 2009; Jaillard et al., 2009; Campanucci et al., 2010; Diano et al., 2011) raised the notion that ROS generation is not merely a by-product of substrate oxidation, but it plays a crucial role in modulating cellular responses involved in the regulation of energy metabolism. We have observed that suppression of ROS levels diminish pro-opiomelanocortin (POMC) cell activation and promote the activity of neuropeptide Y- (NPY)/ agouti related peptide- (AgRP) neurons and feeding, whereas ROS activates POMC neurons and reduces feeding. We found that ROS levels in POMC neurons are positively correlated with leptin levels in lean and ob/ob animals, a relationship that is diminished in diet-induced obese (DIO) mice. Furthermore, high fat feeding resulted in hypothalamic proliferation of peroxisomes and elevated PPAR mRNA levels. Peroxisome proliferation in POMC neurons by the PPAR agonist, rosiglitazone, decreases ROS levels and increases food intake in lean mice on high fat diet. On the other hand, suppression of peroxisome proliferation in the hypothalamus by the PPAR antagonist, GW9662, increases ROS and c-fos expression in POMC neurons, reversed high fat feeding-triggered elevated NPY/AgRP and low POMC neuronal firing, and, resulted in decreased feeding of DIO mice. Intriguingly, central administration of ROS alone increased c-fos and pStat3 expression in POMC neurons and reduced feeding of DIO animals. Taken together these observations gave impetus to the central hypothesis of this application, which is that peroxisome proliferation governed by PPAR in the hypothalamic leptin-targeted neurons confers to cellular leptin resistance. The following specific aims are proposed to test our hypotheses: SPECIFIC AIM 1 to determine the effect of ablation of leptin receptors selectively in AgRP or POMC neurons on high fat diet-induced peroxisome proliferation and impaired hypothalamic neuronal activity. SPECIFIC AIM 2 To assess the effect of selective ablation of PPARgamma in POMC-, AgRP- and leptin receptor -expressing neurons on hypothalamic circuit activity and metabolic phenotype development of mice on standard chow and high fat diet. Understanding hypothalamic sub-cellular mechanisms that underlie cellular and behavioral responses to metabolic alterations will enhance the potential to develop better strategies to combat metabolic disorders, including obesity and diabetes.