METABOLIC SIMILARITIES IN LONG LIVED MODELS

这项拟议研究的总体目标是使用两种哺乳动物模型系统--食物限制(FR)和Ames侏儒(DF)小鼠--识别对延长寿命至关重要的能量代谢和应激反应基因。虽然通过对受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延长寿命有重要作用。一个急需的额外型号是Ames侏儒鼠标。这些突变的小鼠有垂体功能不全，导致生长激素、催乳素和促甲状腺激素减少。DF小鼠模型的寿命大大延长--这是所有哺乳动物模型中最大的延长(Brown-Borg，自然，1996)。指导这项研究的假设是，由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)动物中表达类似的基因，将有很高的可能性对延长寿命至关重要。具体目标1将是比较Ames矮小动物肝脏、肌肉和脂肪组织中三类已知基因的表达水平，以及喂养对照幼崽的FR和随意喂养的小动物的肝脏、肌肉和脂肪组织的表达水平。待检测的已知基因包括：1)参与能量代谢的基因；2)转录因子基因；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酶活性的描述，发现在FR或DF动物中存在不同。通过使用Unigene Mus Musculus基因集的微阵列，特定目标2将扩大在FR和DF小鼠中水平类似变化的基因的筛查。这种已知和未知的基因在矮小和FR小鼠中的表达相似，但与随机喂养的动物不同，这种比较将提出与延长寿命最相关的基因类别。第三个具体目标是确定荷尔蒙不足的其他模型是否延长了寿命。我们将启动两个突变小鼠品系的住房，以确定它们的寿命：Tshb小鼠(缺乏促甲状腺激素β亚基导致甲状腺激素缺乏)和小鼠(缺乏生长激素释放激素受体和生长激素缺乏)。这些动物中的每一种都发育迟缓，但它们的寿命尚不清楚。如果这两个菌株中的任何一个延长了寿命，它们都应该分享与长寿相关的基因座基因表达改变的表型，并将作为描述延长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.