Interaction of caloric restriction with longevity genes

描述(申请人提供)：我们的长期目标是阐明荷尔蒙(胰岛素/IGF-1)信号在哺乳动物衰老和长寿控制中的作用，并确定营养摄入如何与长寿基因相互作用。我们已经证明，限制热量(CR)可以延长Ames侏儒小鼠的寿命，这是一种长寿的甲状腺功能低下突变体，但令人惊讶的是，它未能延长另一种长寿突变体--抗生长激素(GH)的GH受体基因敲除(GHRKO)小鼠的寿命。CR可改善正常小鼠和Ames侏儒小鼠对注射胰岛素的敏感性，但对GHRKO小鼠无影响。我们假设，CR未能延长GHRKO小鼠的寿命是由于极低的胰岛素水平以及CR无法进一步增加这些动物的胰岛素敏感性。我们进一步假设应激抵抗与胰岛素敏感性有关，并且CR不能改善GHRKO小鼠的应激抵抗。这些假说将通过确定胰岛特异性表达IGF-1(被证明可以改善葡萄糖耐量和胰岛素分泌)或使用IGF-1或胰岛素替代治疗是否会使GHRKO小鼠对短期CR的反应正常化来检验。这些治疗的效果将通过测量胰岛素和葡萄糖耐量、肝脏、骨骼肌和心脏中胰岛素相关基因的表达(对CR反应的“分子标记”)、培养的皮肤成纤维细胞和完整小鼠对各种应激源的抵抗力、体温(TCO)的测量以及与胰岛素作用和应激抵抗相关的其他参数的研究来评估。随后，我们将使用最接近于使GHRKO小鼠对短期CR的反应“正常化”的疗法来确定它是否也会导致GHRKO小鼠通过延长寿命来重新获得对慢性CR的反应能力。我们还将在最近培育的GHRH-KO小鼠中检测CR的效果，这些小鼠患有孤立的GH缺乏症，并在表达GH拮抗剂的转基因小鼠中发挥作用。总的来说，这些研究将确定CR对胰岛素信号和应激抵抗的影响，这些信号和应激抵抗在各种不同的基因型别中都与延长寿命一致相关。这些结果将为CR的抗衰老作用机制以及胰岛素水平与应激抵抗、衰老和长寿之间的关系提供新的见解，在当前胰岛素抵抗和代谢综合征的背景下，这是一个在公共卫生中具有重大意义的问题。

DESCRIPTION (provided by applicant): Our long-term goals are to elucidate the role of hormonal (insulin/IGF-1) signaling in the control of aging and longevity in mammals and to determine how nutritional intake interacts with longevity genes. We have shown that caloric restriction (CR) increases longevity in the Ames dwarf mouse, a long-lived hypopituitary mutant, but surprisingly fails to extend longevity in another long-lived mutant, the growth hormone (GH) resistant, GH receptor knockout (GHRKO) mouse. Sensitivity to injected insulin was improved by CR in normal and in Ames dwarf mice but not in GHRKO animals. We hypothesize that failure of CR to prolong life in GHRKO mice is due to extremely low insulin levels and the inability of CR to further increase insulin sensitivity in these animals. We further hypothesize that stress resistance is related to insulin sensitivity and that CR will fail to improve stress resistance in GHRKO mice. These hypotheses will be tested by determining whether pancreatic islet-specific expression of IGF-1 that was shown to improve glucose tolerance and insulin secretion or replacement therapy with IGF-1 or insulin will normalize responses to short-term CR in GHRKO mice. Effects of these treatments will be assessed by measuring insulin and glucose tolerance, expression of insulin-related genes in the liver, skeletal muscle and heart (the "molecular signature" of responses to CR), resistance of cultured skin fibroblasts and intact mice to various stressors, measurements of body core temperature (Tco) and study of other parameters related to insulin action and stress resistance. Subsequently, we will use therapy that most closely "normalizes" the responses to short- term CR in GHRKO mice to determine whether it will also result in GHRKO mice regaining the ability to respond to chronic CR by increasing longevity. We will also examine effects of CR in the recently developed Ghrh-KO mice with isolated GH deficiency and in transgenic mice expressing GH antagonist. Collectively, these studies will identify the effects of CR on insulin signaling and stress resistance that are consistently associated with prolonged longevity across a variety of genotypes. The results will provide novel insights into the mechanisms of anti-aging actions of CR and into the relationship of insulin level and actions to stress resistance, aging and longevity, an issue of major significance in public health in the context of the current "epidemic" of insulin resistance and metabolic syndrome.