METABOLIC SIMILARITIES IN LONG LIVED MODELS

拟议的研究的总体目标是确定基因的能量代谢和应激反应是至关重要的寿命延长使用两种哺乳动物模型系统，食物限制（FR）和艾姆斯侏儒（DF）小鼠。 虽然通过对食物限制的啮齿动物的分析发现了许多生理功能和基因表达的变化，但很难确定哪些变化对寿命延长有显着贡献。 一个非常需要的额外模型是艾姆斯侏儒小鼠。 这些突变小鼠垂体功能不全，导致生长激素、催乳素和促甲状腺激素减少。 df小鼠模型具有显著延长的寿命-任何哺乳动物模型的最大延长（Brown-Borg，Nature，1996）。 指导这项研究的假设是，垂体功能不全状态改变的下游靶基因是长寿的候选基因。 与随意喂养的小鼠相比，在遗传（df）和适应性（FR）动物中表达相似的基因很可能对寿命延长至关重要。具体目标1将是比较艾姆斯侏儒动物与FR和自由采食对照同窝动物肝脏、肌肉和脂肪组织中三类已知基因的表达水平。 待检测的已知基因是1）参与能量代谢的基因，2）已知调节这些组织中代谢基因的营养反应的转录因子基因，和3）参与应激反应途径的基因。 这些基因的选择是基于先前对FR或df动物中发现的不同酶活性的描述。 Specific Aim 2将通过使用UniGene Mus musculus cDNA集的微阵列来扩大FR和df小鼠中水平类似改变的基因的筛选。 这种已知和未知基因的比较，其表达在侏儒和FR小鼠中是相似的，但不同于随意喂养的动物，将表明与寿命延长最相关的基因类别。 第三个具体目标将是确定激素不足的其他模型是否延长了寿命。 我们将开始圈养两种突变小鼠品系，以确定其寿命;即Tshb小鼠（促甲状腺激素β亚基缺陷导致甲状腺激素缺乏）和Little小鼠（缺乏生长激素释放激素受体和生长激素缺陷）。 这些动物都是生长迟缓，但他们的寿命是未知的。 如果这些菌株中的任何一个具有增加的寿命，则它们应该共享与寿命相关的基因座的改变的基因表达的表型，并且将作为描绘增加寿命的基因表达模式的额外模型。

The overall goal of the proposed research is to identify the genes in energy metabolism and stress response that are crucial for life span extension using two mammalian model systems, food restriction (FR) and the Ames dwarf (df) mouse. Although many changes in physiologic function and gene expression have been found through the analysis of rodents subjected to food restriction, it is difficult to identify which changes contribute significantly to life span extension. A much needed additional model is the Ames dwarf mouse. These mutant mice have pituitary insufficiency leading to reduced growth hormone, prolactin, and thyrotropin. The df mouse model has a dramatically extended life span--the greatest extension of any mammalian model (Brown-Borg, Nature, 1996). The hypothesis that directs the proposed studies is that downstream target genes altered by the pituitary insufficiency state are candidate genes for longevity. Genes that are similarly expressed in the genetic (df) and in the adaptive (FR) animals compared to ad libitum fed mice, will have a high probability of being critical for the life span extension. Specific Aim 1 will be to compare the levels of expression of three categories of known genes in liver, muscle, and adipose tissues of the Ames dwarf animals to that of the FR and ad libitum fed control litter mates. The known genes to be examined are those that are 1) involved in energy metabolism 2) transcription factor genes known to regulate the nutritional response of metabolic genes in these tissues and 3) genes involved in stress response pathways. These genes are chosen based on previous descriptions of enzymatic activities found to differ in either the FR or df animals. Specific Aim 2 will expand the screen for genes whose levels are similarly altered in the FR and df mice by using micro array of the UniGene Mus musculus cDNA set. This comparison of known and unknown genes whose expression is similar in dwarf and FR mice, but differs from ad lib fed animals will suggest categories of genes that are most relevant to the extension of life span. A third specific aim will be to determine whether additional models of hormonal insufficiency have extended life spans. We will initiate the housing of two mutant mouse strains in order to determine their longevity; i.e. the Tshb mouse (deficient in the beta subunit of thyrotropin resulting in thyroid hormone deficiency) and the Little mouse (lacking the growth hormone releasing hormone receptor and deficient in growth hormone). Each of these animals is growth retarded, but their longevity is unknown. If either of these strains has increased longevity, they should share the phenotype of altered gene expression for loci relevant to longevity and will serve as an additional model to delineate patterns of gene expression that increase life span.