Age-related changes in glutathione synthesis

描述(申请人提供)：氧化应激被认为是导致特定疾病的开始或进展以及衰老的一般过程的机制之一。谷胱甘肽(GSH)是一种存在于所有哺乳动物细胞中的高浓度三肽，是人体内主要的内源性抗氧化剂，在解毒反应和保护细胞免受氧化剂的毒性作用中发挥着至关重要的作用。体内GSH储存的维持是一个复杂的综合现象，人们对可能调节全身和特定组织和细胞中GSH水平的潜在干预措施重新产生了兴趣。已知的年龄增长与氧化应激增加有关，据报道也与低GSH浓度有关。此外，衰老与心血管疾病、糖耐量受损和糖尿病的患病率增加有关；后者也被证明伴随着较低的GSH浓度。可能导致谷胱甘肽状态受损的机制包括合成减少和/或相对于合成能力的利用增加。理想情况下，人们希望测量体内GSH合成和利用的速率。不幸的是，消耗GSH的多种途径，以及组织的多样性，使得对人类所有不同途径的利用进行有意义的同时测量是不可能的。因此，这项提案的重点将放在GSH合成率上。我们计划测试以下假设：1)与年轻(35岁)受试者相比，老年男性和女性(60岁以上)的GSH合成率和GSH水平较低，这些差异将因老年人的糖尿病而加剧；2)半胱氨酸前体的提供将减弱这些差异。半胱氨酸是GSH合成中的限速氨基酸。具体目的是：1)用稳定同位素示踪法测定非糖尿病男性和女性年轻组和老年组的GSH合成率，以及这些志愿者血浆和红细胞中的GSH浓度。2)糖尿病对老年男性和女性GSH合成速率和浓度的影响。3)对乙酰氨基酚耗竭GSH对青年和老年非糖尿病患者GSH合成率的影响。4)醋氨酚耗竭GSH对老年非糖尿病患者和糖尿病患者GSH合成率的影响。5)急性给予半胱氨酸前体L-2-氧噻唑烷-4-羧酸(OTZ)是否会增加青年和老年非糖尿病志愿者的GSH合成率和GSH水平。6)急性给予半胱氨酸前体OTZ是否会增加GSH合成率和GSH水平7老年非糖尿病和糖尿病男性和女性。这些体内研究中获得的数据将有助于在人类身上整合在动物实验和体外细胞培养系统中获得的不同结果，并提高我们对衰老对人类GSH动态平衡的影响的基本理解。人们希望，这些数据将为未来研究营养补充剂的有效性奠定基础，这些营养补充剂旨在调节个人的GSH状态，并可能改善氧化应激的有害影响。

DESCRIPTION (provided by applicant): Oxidative stress is thought to be one of the mechanisms leading to the initiation or progression of specific diseases as well as to the general process of aging. Glutathione (GSH), a tripeptide present in high concentrations in all mammalian cells, is the body's major endogenous antioxidant and plays a vital role in detoxification reactions and in the protection of cells from the toxic effects of oxidants. Maintenance of body GSH stores is a complex, integrated phenomenon, and there has been a resurgence of interest in potential interventions that may modulate GSH levels in the whole body and in specific tissues and cells. Advancing age, known to be associated with increased oxidative stress, is also reported to be associated with low GSH concentrations. In addition, aging is associated with an increased prevalence of cardiovascular disease, impaired glucose tolerance, and diabetes mellitus; the latter has also been shown to be accompanied by lower GSH concentrations. The mechanisms that could be responsible for a compromised GSH status include decreased synthesis and/or increased utilization relative to synthetic capacity. Ideally, one would like to measure in vivo rates of both GSH synthesis and utilization. Unfortunately, the multitude of pathways consuming GSH, as well as tissue variation, makes it impossible to have meaningful simultaneous measurements of utilization by all of the different pathways in the human. Hence, the focus of this proposal will be on GSH synthesis rates. We plan to test the hypotheses that 1) older men and women (age 60+ years) will have lower GSH synthesis rates and lower GSH levels compared to younger (<35 years) subjects and these differences will be exacerbated by diabetes mellitus in the old and 2) the provision of precursors for cysteine, the rate-limiting amino acid in GSH synthesis, will attenuate these differences. The specific aims are to determine: 1) Rates of GSH synthesis in younger and older groups of non-diabetic men and women using stable isotope tracer methodology, and GSH concentrations in plasma and erythrocytes of these volunteers. 2)The effect of diabetes mellitus on GSH synthesis rates and concentrations in older men and women. 3)The effect of GSH depletion by acetaminophen on rates of GSH synthesis in young and old non-diabetics. 4) The effect of GSH depletion by acetaminophen on rates of GSH synthesis in older non-diabetics and diabetics. 5) Whether acute administration of the cysteine precursor, L-2-oxothiazolidine-4-carboxylic acid (OTZ), will increase rates of GSH synthesis and GSH levels in young and old non-diabetic volunteers. 6) Whether acute administration of the cysteine precursor, OTZ, will increase rates of GSH synthesis and GSH levels 7 older nondiabetic and diabetic men and women. Data obtained in these in vivo studies will help to integrate in humans the diverse findings obtained in experiments conducted in animals and from in vitro cell culture systems and to improve our fundamental understanding of the effect of aging on GSH homeostasis in humans. It is hoped that the data will lay the groundwork for future studies examining the efficacy of nutritional supplements aimed at modulating an individual's GSH status and potentially ameliorating the deleterious effects of oxidative stress.