In Vivo Regulation of Protein Turnover by Hormones

描述（由申请人提供）：我们将首先确定高肌肉线粒体容量的人是否在摄入高脂肪饮食时产生更多的活性氧（ROS），从而表现出更高的细胞氧化损伤。我们以前发现，亚洲印度移民尽管有严重的胰岛素抵抗，但线粒体容量很高。索马里人是另一个糖尿病发病率迅速上升的新移民人口。这两个群体传统上都吃低热量密度的饮食，我们假设当这些群体暴露于高热量的西方饮食时，他们表现出增加的氧化应激、氧化损伤和胰岛素抵抗。我们将比较年龄、体重指数和性别相匹配的亚裔印度人、索马里人和东北部美国人。我们将测量高脂肪膳食后骨骼肌中活性氧的产生。我们将比较两周高脂饮食和低脂饮食对这三个人群的蛋白质、DNA和脂质的氧化损伤。我们将确定这些人群中氧化损伤水平升高是否伴随着线粒体容量高、ros释放电位高和胰岛素敏感性低于NE。其次，该提案将应用我们实验室开发的一种新方法来确定患有严重胰岛素抵抗，高胰岛素水平和氧化应激的腹部肥胖患者是否积累了可能导致有害功能后果的老化和受损的肌肉和血浆蛋白。我们将确定通过提高胰岛素敏感性来降低循环胰岛素和氧化应激是否会减少肌肉和血浆中老化和受损蛋白质的积累。我们假设三种不同的增强胰岛素敏感性的模式通过不同的机制来减少老化和受损蛋白质的积累和DNA氧化。我们期望热量限制（CR）通过减少ROS的产生来减少氧化应激，从而减少对蛋白质和DNA的氧化损伤。相反，有氧运动增加活性氧的产生，但刺激一个强大的抗氧化防御系统。此外，与CR不同，我们希望运动能增加新生蛋白质的合成和旧的、受损的蛋白质的周转。胰岛素增敏剂可以减少氧化应激，增强对老化和受损蛋白质的清除。我们将研究腹部肥胖的人，并将他们与瘦的参与者进行比较，以确定这些胰岛素抵抗的人是否比瘦的胰岛素敏感的人积累了更多的受损蛋白质和DNA。然后，我们将确定16周的有氧运动、热量限制和胰岛素增敏剂与安慰剂是否会减轻对蛋白质和DNA的氧化损伤，并改善胰岛素敏感性。拟议的研究将使用最先进的方法进行，其中许多方法是在上一个资助期间在我们的实验室开发的。我们希望这些研究的结果能够为胰岛素抵抗和2型糖尿病的潜在机制提供开创性的见解，并证明功能蛋白质组在体内维持的机制。

DESCRIPTION (provided by applicant): We will first determine whether people with high muscle mitochondrial capacity produce higher amount of reactive oxygen species (ROS) on consuming high fat diet and thus exhibit elevated cellular oxidative damage. We previously found that Asian Indian immigrants have high mitochondrial capacity in spite of severe insulin resistance. Somalians are another new immigrant population with rapidly increasing prevalence of diabetes. Both of these groups traditionally consume low caloric density diets, and we hypothesize that when these groups are exposed to high-calorie Western diets, they exhibit increased oxidative stress, oxidative damage, and insulin resistance. We will compare Asian Indians, Somalians, and NE Americans who are matched for age, BMI, and sex. We will measure ROS production in skeletal muscle following high fat meal. We will compare the oxidative damage to proteins, DNA, and lipids in these three populations following 2 weeks of high fat diet in comparison with low fat diet. We will determine if elevated levels of oxidative damage in these populations is accompanied by high mitochondrial capacity, higher ROS-emitting potential, and lower insulin sensitivity than NE. Secondly the proposal will apply a novel method developed in our laboratory to determine whether abdominally obese people with severe insulin resistance, high insulin levels, and oxidative stress accumulate old and damaged muscle and plasma proteins that may cause deleterious functional consequences. We will determine whether decreasing circulating insulin and oxidative stress by enhancing insulin sensitivity decreases the accumulation of old and damaged protein in muscle and plasma. We hypothesize that three different modes of enhancing insulin sensitivity act by different mechanisms to decrease the accumulation of old and damaged proteins and DNA oxidation. We expect caloric restriction (CR) to reduce oxidative stress by reducing ROS production and thus decrease oxidative damage to proteins and DNA. In contrast aerobic exercise increases ROS production but stimulates a robust antioxidant defense system. Furthermore, unlike CR we expect exercise to increase the synthesis of nascent proteins and turnover of old, damaged proteins. Insulin sensitizers reduce oxidative stress and enhance clearance of old and damaged protein. We will study abdominally obese people and compare them with lean participants to determine whether these insulin resistant people accumulate more damaged proteins and DNA in comparison with lean insulin sensitive people. We will then determine whether 16 weeks of aerobic exercise, caloric restriction and insulin sensitizers versus placebo will attenuate oxidative damage to proteins and DNA and improve insulin sensitivity. The proposed studies will be performed utilizing the state-of-the-art methods many of which were developed in our laboratory during the previous funding period. We expect the results from these studies to provide seminal insights into the underlying mechanism of insulin resistance and type 2 diabetes, in addition to demonstrating mechanisms by which a functional proteome is maintained in vivo. PUBLIC HEALTH RELEVANCE: The proposed experiments investigate the potential novel underlying mechanisms of rapidly expanding prevalence of diabetes and related health problems in the society. First specific aim is to determine whether more efficient mitochondria, the powerhouse of cell that produce chemical energy, causes adverse effects on DNA and protein when transitioning from a diet of low calorie content to that of high energy content. The second and third aims are to measure the accumulation of damaged and old proteins in muscle and plasma, using a novel methodology in obese and insulin resistant people and to determine how this potentially deleterious process is altered by aerobic exercise, caloric restriction, and medication that enhance insulin sensitivity and reduce high insulin levels.