Molecular Mechanisms of Longevity in Long-Lived Mice

描述（由申请人提供）：小鼠中少量自然发生和工程突变导致寿命延长。功能性生长激素（GH）缺乏与至少四种小鼠的寿命增加有关，其中两种，Ames （Prop1df/df）和Little （Ghrhrlit/lit）小鼠，我们进行了深入研究。对生长激素缺乏、长寿小鼠以及热量限制（因此长寿）小鼠肝脏的整体基因表达分析显示，寿命延长与属于外源性或解毒代谢类别的基因升高之间存在相关性。内源性代谢中间体的解毒是肝脏的主要功能。该途径由转运蛋白、细胞色素、转移酶和输出蛋白组成，当核激素受体（nhr）被胆汁酸、类固醇、维生素和脂类等内源性化合物激活后，它们就受到nhr的转录调节。秀丽隐杆线虫的长寿突变体也显示出类似的nhr、细胞色素和转移酶的升高（23,24）。在本研究中，我们将验证一种假设，即在生长激素缺乏的长寿小鼠中观察到的外源代谢的慢性激活有利于长寿。Specific Aim 1将使用突变小鼠系（敲除细胞色素7b1）来模拟在长寿小鼠中发现的解毒途径的变化。这种基因敲除小鼠模型具有与生长激素缺陷小鼠相似的异种代谢基因升高的模式。将检查Cyp 7b1缺失小鼠的寿命延长情况。Specific Aim 2旨在通过检测双KO和三KO小鼠对nhr的需求，以及敲低肝脏中特定nhr和候选转录因子，阐明控制解毒反应基因激活的分子机制。最后，将通过基因表达阵列评估肝脏中Stat Sab信号减少的后果，以确定肝脏中Stat Sab的减少是否占生长激素缺乏Ames和Little小鼠中大部分基因表达变化的原因，并确定潜在的共同调节因子。这些目标将直接测试外源代谢的慢性激活是否会影响寿命，并将阐明可能成为干预衰老过程有用点的分子靶点。

DESCRIPTION (provided by applicant): A small number of naturally occurring and engineered mutations in mice result in extension of lifespan. Functional growth hormone (GH) deficiency has been associated with increased longevity in at least four strains of mice, two of which, the Ames (Prop1df/df) and Little (Ghrhrlit/lit) mice, we have studied intensively. Global gene expression analysis of the liver in GH deficient, long-lived mice, as well as calorically restricted (and thus long-lived) mice, shows a correlation between increased lifespan and elevation of genes which belong to the category of xenobiotic or detoxification metabolism. Detoxification of endogenous metabolic intermediates is a major function of the liver. This pathway is comprised of transporters, cytochromes, transferases, and exporters which become transcriptionally regulated by nuclear hormone receptors (NHRs) upon activation of the NHRs by several endogenous compounds including bile acids, steroids, vitamins, and lipids. Long-lived mutants of C. elegans show similar elevations of NHRs, cytochromes, and transferases (23, 24) In this proposal, we will test the hypothesis that chronic activation of xenobiotic metabolism as seen in the GH deficient, long-lived mice, is beneficial to longevity. Specific Aim 1 will use a mutant mouse line (a knockout of cytochrome 7b1) that mimics the changes in detoxification pathways that are found in the long-lived mice. This knockout mouse model has patterns of elevation of xenobiotic metabolism genes similar to the GH deficient mice. The Cyp 7b1 null mice will be examined for longevity extension. Specific Aim 2 is designed to elucidate the molecular mechanisms that control the activation of the detoxification response genes by examining the requirement for NHRs in double and triple KO mice and by knockdown of specific NHRs and candidate transcription factors in the liver. Finally, the consequences of reduction of Stat Sab signaling in the liver will be assessed by gene expression arrays to determine whether or not a reduction in Stat Sab in the liver accounts for the majority of gene expression changes seen in the GH deficient Ames and Little mice, and to identify potential co-regulators. These aims will directly test whether or not chronic activation of xenobiotic metabolism impacts lifespan and will elucidate molecular targets that may be useful points of intervention in the aging process.