1a. Objectives (from AD-416)
1. Determine the extent to which dietary antioxidants alter obesity-induced and/or exercise-induced changes in mitochondrial function and insulin sensitivity. Sub-objective 1A. Determine the influence of anti-oxidant supplementation on changes in insulin sensitivity induced in the rat by high dietary fat and exercise. Sub-objective 1B. Determine the degree to which anti-oxidant supplementation alters exercise-induced changes in insulin sensitivity and mitochondrial function responses of overweight/obese individuals. 2. Identify sites and causes of obesity-induced and exercise-induced oxidative stress. Sub-objective 2A. Determine the effects of obesity and exercise on the temporal and cellular activation of the nuclear factor (erythroid-derived 2)-like 2 (Nrf-2)/Anti-oxidant Response Element pathway. Sub-objective 2B. Identify and characterize obesity-induced and exercise-induced oxidative changes to insulin signaling pathway proteins. 3. Identify, characterize and compare sites of obesity-induced versus exercise-induced mitochondrial respiratory changes. Sub-objective 3A. Determine the degree to which anti-oxidant supplementation blunts exercised-induced and obesity-induced changes in mitochondria.
1b. Approach (from AD-416)
In order to complete the objectives of this proposal, we will utilize a combination of studies in humans, rodents that examine physiologic, metabolomic, genetic, and proteomic endpoints. In Objective 1, we will perform studies in humans and rodents to determine how antioxidant (vitamin E and vitamin C) supplementation affects insulin responses to exercise and obesity. The study in humans will involve analysis of exercise adaptation and insulin responses in previously untrained individuals and if antioxidant supplementation either enhances or negates these adaptations. Rodent studies will further examine molecular mechanisms underlying these adaptations. In Objective 2, we will determine the extent to which obesity, exercise, and anti-oxidant supplementation alter redox balance in animals and specific cells and to identify specific proteins whose thiol redox status is altered in obesity, exercise, and anti-oxidant supplementation. These studies will utilize transgenic mouse models and proteomic approaches. In Objective 3, we will determine the extent to which obesity, exercise, and anti-oxidant supplementation alter mitochondrial function. These studies will utilize rat models of exercise and obesity. Whole tissue and isolated mitochondria will be studied for changes in total mitochondrial content, mitochondrial gene expression, and respiration, and mitochondrial enzyme activities.
3. Progress Report
During FY 2011, the project team made progress in multiple areas. Objective 1A. We performed studies in rats testing the hypothesis that vitamin C and vitamin E supplementation prevents glucose intolerance in obese rats. We are currently analyzing the samples and data. We will test the hypothesis that vitamin C and vitamin E supplementation prevents exercise adaptations in rats in the FY 2012. This work will provide data to support/refute the role of anti-oxidant supplements as adjuncts to treatment of obesity or enhancing the effects of exercise. As an ancillary study, we demonstrated that the anti-oxidant defense enzyme, methionine sulfoxide reductase, was reduced selectively in visceral adipose tissue as a result of obesity. This work impacts the understanding of how obesity changes the body’s response to oxidant stress and that obesity decreases this response in specific tissues. Objective 1B. The human study protocol to examine the role of anti-oxidant supplementation (vitamin C and vitamin E) on exercise adaptations was completed and approved by the IRB of the University of North Dakota. We have begun recruiting and entering volunteers into the study. This study investigates whether anti-oxidant supplementation (vitamins C and E) modulate exercise responses particularly with respect to blood sugar regulation in overweight/obese people. This work will provide data to support/refute the role of anti-oxidant supplements as adjuncts to treatment of obesity or enhancing the effects of exercise. Objective 2A. Tests the hypothesis that exercise and nutritional factors regulate cellular redox status in tissue specific ways. To test this hypothesis, we have started and are growing the Anti-oxidant Reporter Element (ARE)-reporter mouse colony. We started a colony of Nrf2 null mice. These mice lack the transcription factor that activates the ARE. Nrf2 is nutritionally regulated and our initial data indicate that Nrf2-ARE pathway regulates energy metabolism and body composition. This work is currently being prepared for submission to an international meeting. Objective 2B. Tests the hypothesis that protein thiols undergo greater oxidative as a result of obesity and exercise in animals. We have developed novel methods for measurement of thiol oxidation in tissues such as muscle, adipose, and liver. This work is currently being prepared for publication and presentation at an international meeting. This research project includes an ancillary project examining the role of Atlantic salmon consumption as a means to increase omega 3 fatty acids in humans. This project is a collaboration with the ARS-National Cold Water Aquaculture Center in Franklin, ME. We have finished collecting volunteer samples and are now analyzing data. We have submitted one paper examining the extent to which baking of Atlantic salmon increases fatty acid oxidation. This paper demonstrates that baking salmon decreases the presence of fatty acid oxidation products and does not decrease the content of beneficial omega-3 fatty acids in salmon. This work had broad health impact for the American public and will benefit the cold water fish industry.
1. Obesity reduces anti-oxidant defenses in fat tissue. Obesity induces oxidative stress in the body. However, the effects of this oxidative stress in obesity are not clear. ARS researchers in Grand Forks, ND, demonstrated that obesity reduces the activity of the anti-oxidant defense protein methionine sulfoxide reductase (MSR) in fat stores associated with inflammation and insulin resistance. Methionine sulfoxide modification is an inhibitor of enzyme activity and MSR activity removes this inhibition. These data are useful in understanding the impact of obesity upon fat stores and future studies examining how cellular metabolism changes with obesity.
2. Baking farm-raised Atlantic salmon retains health-promoting omega-3 fatty acids. Eating seafood enriched in omega-3 fatty acids is known to reduce risk for cardiovascular disease and diabetes. It is not known whether baking of farm-raised Atlantic salmon, a good source of omega-3’s, causes loss of these omega-3s and increases levels of potentially toxic omega-3 oxidation by-products. ARS researchers in Grand Forks, ND, demonstrated that baking actually reduces the content of oxidation products and retains the levels of parent omega-3 fatty acids. This work will benefit the dietitians, nutritionists, health-care providers, and ultimately consumers who wish to increase the consumption of salmon and other omega-3 rich seafood for health benefit.Long, E.K., Picklo, M.J. 2010. Trans-4-hydroxy-2-hexenal, a product of n-3 fatty acid peroxidation: make some room HNE…. Free Radical Biology and Medicine. 49(1):1-8.