Role of growth hormone in thiol metabolism, stress resistance and aging

描述（由申请人提供）：本提案的长期目标是描述生长激素缺乏对线粒体功能，抗逆性和健康寿命的有益影响的机制。我们的研究一直集中在理解长寿动物的假设，巯基代谢的上调导致对细胞压力的更大保护。申请人的工作已经证明生长激素（GH）和igf - 1是长寿保障的主要参与者。患有遗传性侏儒症（Ames）的小鼠和缺乏功能性生长激素受体（GHRKO）的小鼠分别表现出生长激素缺乏或抗性、衰老延迟和抗逆性增强。需要测试的全球假设是，硫醇代谢在衰老中起着关键作用，生长激素调节这一途径的关键组成部分，最终导致健康寿命（通过抗应激/保护）和寿命的变化。因此，生长激素信号的减少为矮鼠提供了一种生物学优势，可以更好地清除有毒代谢副产物，改变线粒体功能并延长寿命。为了进一步解决和定义这一全球假设，本提案将测试两个有效的假设，这两个假设都关注生长激素、硫醇代谢和衰老之间的关系。首先，线粒体对分子损伤的易感性是由生长激素和硫醇代谢机制控制的，包括蛋白质s -硫代化和谷胱甘肽s -转移酶（GST）的表达。因此，线粒体GSH/GSSG增加导致呼吸链复合物谷胱甘肽化增加。这种蛋白质修饰使这些蛋白质更能抵抗ros诱导的蛋白质水解降解，这表明谷胱甘肽化具有保护作用，并代表了细胞抗逆性的关键机制。一些GST（解毒的关键）受生长激素调节，表达水平指示疾病易感性，但对生长激素、GST与衰老之间的关系知之甚少。第二个假设是硫醇代谢和DNA甲基化模式是由循环生长激素水平和膳食蛋氨酸（MET）决定的。MET代谢途径在Ames小鼠中高度上调，导致谷胱甘肽升高和DNA甲基化差异。在本项目中，申请人计划通过以下方式阐明生长激素、硫醇代谢和细胞保护之间的关系：1)将侏儒小鼠呼吸和抗氧化活性的增强与线粒体GSH和谷胱甘肽化的增加直接联系起来；2)提供直接证据，证明GH的缺乏是商品及服务税制度具体增强的原因；3)确定饮食MET改变后与抗逆性和寿命相关的硫醇代谢变化；4)建立长寿小鼠的第一个表观基因组图谱。确定gh依赖的途径和机制可能为治疗干预提供建议，以增强抗逆性，延缓衰老，治疗衰老相关疾病并延长人类的健康寿命。公共卫生相关性：本提案旨在确定生长激素对两种长寿小鼠品系（Ames侏儒小鼠和生长激素受体敲除小鼠）抗应激和长寿相关过程的影响。确定gh依赖的途径和机制可能为延缓衰老、治疗衰老相关疾病和延长人类寿命提供潜在的治疗干预措施。

DESCRIPTION (provided by applicant): The long-term objective of this proposal is to delineate mechanisms of the beneficial effects of growth hormone deficiency on mitochondrial function, stress resistance and health span. Our research has been focused on understanding the hypothesis that in long living animals, an upregulation of thiol metabolism leads to greater protection from cellular stress. The applicant's work has established that growth hormone (GH) and IGF-I are major players in longevity assurance. Mice with hereditary dwarfism (Ames) and those that lack a functional GH receptor (GHRKO) exhibit GH deficiency or resistance (respectively), delayed aging, and enhanced stress resistance. The global hypothesis to be tested is that thiol metabolism plays a key role in aging and that GH modulates key components of this pathway ultimately leading to changes in health span (via stress resistance/protection) and lifespan. Thus, reduced GH signaling confers a biologic advantage to dwarf mice leading to better scavenging of toxic metabolic byproducts, altered mitochondrial function and enhanced longevity. To further address and define this global hypothesis, two working hypotheses will be tested in this proposal, both of which focus on the relationship between GH, thiol metabolism and aging. The first is that the susceptibility of mitochondria to molecular insults is controlled by mechanisms that involve GH and thiol metabolism including protein S-thiolation and gluta- thione S-transferase (GST) expression. As such, increased mitochondrial GSH/GSSG leads to increased glutathionylation of respiratory chain complexes. This protein modification renders these proteins more resistant to ROS-induced proteolytic degradation suggesting a protective role of glutathionylation and represents a key mechanism of cellular stress resistance. Some of the GSTs (key for detoxification) are regulated by GH and expression levels are indicative of disease susceptibility but little is known about the relationship between GH, GST and aging. The second hypothesis is that thiol metabolism and DNA methylation patterns are determined by circulating GH levels and dietary methionine (MET). The MET metabolic pathway is highly upregulated in Ames mice resulting in increased GSH and differential DNA methylation. In this project, the applicant plans to elucidate the relationship between GH, thiol metabolism and cellular protection by: 1) directly linking the enhanced respiratory and antioxidative activities in dwarf mice to increased mitochondrial GSH and glutathionylation of these proteins; 2) providing direct evidence that the lack of GH is responsible for substrate-specific enhancement of the GST system; 3) defining the changes in thiol metabolism linked to stress resistance and longevity following altered dietary MET; and 4) establishing the first epigenomic profile of a long-living mouse. Determining GH-dependent pathways and mechanisms may suggest therapeutic interventions to enhance stress resistance, delay aging, treat aging-related disorders and extend health span in humans. PUBLIC HEALTH RELEVANCE: This proposal is designed to determine the influence of growth hormone on processes related to stress resistance and longevity using two long-living mouse strains, Ames dwarf and growth hormone receptor knockout mice. Determining GH-dependent pathways and mechanisms may suggest potential therapeutic interventions to delay aging treat aging-related disorders and extend life span in humans.