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.

National Institute of Health (NIH)
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Research Project (R01)
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Clinical and Integrative Diabetes and Obesity Study Section (CIDO)
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Laughlin, Maren R
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Mayo Clinic, Rochester
United States
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