Role of Peroxisome Proliferation in Leptin Resistance

描述（由申请人提供）：为了了解代谢紊乱（包括肥胖和II型糖尿病）的病因，我们必须更好地了解储存的 可用的能量来源由中枢神经系统监控。特别是，精细的细胞相互作用和细胞内的机制，使适当的下丘脑和随之而来的内分泌和行为反应的循环激素和营养信号的理解仍然难以捉摸。最近的数据，包括来自我们实验室的数据（Andrews等人，2008; Benani等人，2007;安德森等人，2009; Jaillard等人，2009; Campanucci等人，2010; Diano等人，2011）提出了这样的概念，即ROS的产生不仅仅是底物氧化的副产物，而且它在调节参与能量代谢调节的细胞反应中起着至关重要的作用。我们已经观察到，ROS水平的抑制减少前阿黑皮素（POMC）细胞活化，并促进神经肽Y-（NPY）/AgRP相关肽-（AgRP）神经元的活性和进食，而ROS激活POMC神经元，减少进食。我们发现POMC神经元中的ROS水平与瘦和肥胖/肥胖动物中的瘦素水平呈正相关，这种关系在饮食诱导的肥胖（DIO）小鼠中减弱。此外，高脂喂养导致下丘脑过氧化物酶体增殖和PPARγ mRNA水平升高。在高脂饮食的瘦小鼠中，通过PPARγ激动剂罗格列酮在POMC神经元中的过氧化物酶体增殖降低ROS水平并增加食物摄入。另一方面，抑制过氧化物酶体增殖在下丘脑的过氧化物酶体拮抗剂，GW 9662，增加ROS和c-fos的表达在POMC神经元，逆转高脂肪喂养引发的升高的NPY/AgRP和低POMC神经元放电，并导致减少喂养的DIO小鼠。有趣的是，单独的ROS中枢给药增加了POMC神经元中c-fos和pStat 3的表达，并减少了DIO动物的进食。总之，这些观察结果推动了本申请的中心假设，即下丘脑瘦素靶向神经元中由PPARγ控制的过氧化物酶体增殖赋予细胞瘦素抗性。提出了以下具体目标来检验我们的假设：具体目的1确定选择性消融AgRP或POMC神经元中的瘦素受体对高脂饮食诱导的过氧化物酶体增殖和受损的下丘脑神经元活性的影响。具体目的2评估选择性消融POMC、AgRP和瘦素受体表达神经元中的PPARgamma对标准食物和高脂饮食小鼠下丘脑回路活动和代谢表型发育的影响。了解下丘脑亚细胞机制是代谢改变的细胞和行为反应的基础，将提高开发更好的策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 PPARγ mRNA levels. Peroxisome proliferation in POMC neurons by the PPARγ 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 PPARγ 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.