The overall aim of this proposal is to develop and characterize direct, objective in vivo biomarkers of oxidative stress occurring in diabetes mellitus. Such biomarkers would be valuable for monitoring long-term ongoing changes and complications that result from prolonged hyperglycemia and associated oxidative stress. We focus on two major antioxidants, glutathione (GSH) and vitamin C (ascorbate, Asc), that have received interest from the medical community as potential markers of oxidative stress to elucidate their role in diabetes and to provide new insights into diabetes care. Diabetes, one of the most common diseases in the US, is characterized by insulin insufficiency or resistance and hyperglycemia, which induce oxidative stress and lead to impaired antioxidant defense. GSH and Asc are the major antioxidants and play a central role in the antioxidant defense system. Also, there is a dynamic metabolic interaction between these antioxidants, which form the antioxidant network. GSH has been identified as a sensitive indicator of oxidative stress. Asc is the major antioxidant besides GSH, and has the neuroprotective role. Levels of Asc have been used as a marker for oxidative status in peripheral tissues and to evaluate the outcome of Asc treatments in diseases such as diabetes and cancer. To date, however, there has been no direct noninvasive measurement of GSH and Asc in any living tissues of the pathologic brain including diabetes due to the scarcity of available techniques. Therefore, the development of completely noninvasive and quantitative techniques for measuring these antioxidants would be a highly significant advance for accurate assessment. Recently we established the feasibility of GSH and Asc mapping in the human brain using novel magnetic resonance techniques: selective multiple quantum chemical shift imaging. Using these unique imaging techniques as a robust tool for clinical studies in diabetes, we will characterize the usefulness of our imaging approach by investigating cerebral antioxidant levels in situ.
The aims of this project are: (1) to determine cerebral concentrations of two major antioxidants (GSH and Asc) in the living brains of normal controls and type 2 diabetic patients, and (2) to quantify the effect of chronic hyperglycemia on cellular uptake of Asc across the blood-brain barrier. A well characterized non-invasive biomarker of oxidative stress will not only provide new insights into the role of antioxidants in diabetes but also play a vital role in the development of therapeutic strategies and the evaluation of the efficacy of antioxidant treatments for diabetes.
The identification of a sensitive biomarker of oxidative stress in diabetes will provide a means to track the progression of the disease and the degree to which treatments are effective. Since a biomarker of oxidative stress may provide information on changes in antioxidant levels in the brain of diabetic patients, patients who are lacking in antioxidants can be identified and receive treatments. Therefore, complications resulting from diabetes will be reduced which will be an important factor in improving public health.
| Ma, Yan; Sullivan, Garrett G; Schrick, Elizabeth et al. (2013) A convenient method for measuring blood ascorbate concentrations in patients receiving high-dose intravenous ascorbate. J Am Coll Nutr 32:187-93 |
| Wang, Wen-Tung; Lee, Phil; Yeh, Hung-Wen et al. (2012) Effects of acute and chronic hyperglycemia on the neurochemical profiles in the rat brain with streptozotocin-induced diabetes detected using in vivo ýýH MR spectroscopy at 9.4 T. J Neurochem 121:407-17 |
