In Vivo Regulation of Protein Turnover by Hormones

Mayo Clinic Rochester, Rochester MN

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Abstract

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.