Yoo, Elsia2015-08-052015-08-0520122012(ALMA)contemphttps://hdl.handle.net/2144/12691Thesis (M.A.)--Boston University PLEASE NOTE: Boston University Libraries did not receive an Authorization To Manage form for this thesis or dissertation. It is therefore not openly accessible, though it may be available by request. If you are the author or principal advisor of this work and would like to request open access for it, please contact us at open-help@bu.edu. Thank you.Background: Hepatic steatosis is considered to be a physical manifestation of insulin resistance and continues to increase in prevalence with the rise in obesity. The accumulation of fat in liver contributes to hepatic oxidative stress through lipid induced ROS production. Oxidative stress responses affect the cytosolic and mitochondrial redox states represented by circulating redox metabolite pairs: lactate/pyruvate and β-hydroxybutyrate/acetoacetate. The lactate to pyruvate ratio (L/P) reflects the cytosolic [NAD+]/[NADH] state and the β-hydroxybutyrate to acetoacetate ratio (B/A) is an indicator of the mitochondrial [NAD+]/[NADH] state. The major extracellular and intracellular thiol-disulfide couples, Cys/CySS and GSH/GSSG, respectively, are also thought to mediate oxidative stress responses. The aim of this study is to determine if thiol-disulfide couples at varying oxidative values can cause changes in fatty liver cellular redox states. Methods: Oleic acid was used to induce lipid accumulation in primary mouse hepatocytes and then the thiol-disulfide couples were applied extracellularly across a physiological range. A ROS sensitive fluorescent dye, dichlorodihydrofluorescein, was used to measure H2O2 production in the presence of different ratios of Cys/CySS and GSH/GSSG. The circulating metabolites (lactate, pyruvate, β-hydroxybutyrate and acetoacetate) released from hepatocytes were measured in the cell media using fluorescence assays, in order to determine the cytosolic and mitochondrial redox states. Results: Both oleic acid and the mixture of palmitic acid and oleic acid were found to create an in vitro model of hepatic steatosis (p less than 0.05). The thiol-disulfide couple Cys/CySS decreased ROS production at the reduced states of -150 mV and Cys 200 μM (p less than 0.01). In the GSH/GSSG couple, any addition of GSH reduced ROS production (p less than 0.01). The UP ratios increased significantly with the addition of fatty acid in both the Cys/CySS (p less than 0.05) and GSH/GSSG (p less than 0.05) experiments. The B/A ratios increased significantly with fatty acid addition in two of the Cys/CySS conditions, -80 mV and 0 mV {p less than 0.05), and in all of the GSH/GSSG conditions (p less than 0.001). Conclusion: The thiol-disulfide couples can modulate the effects of lipid metabolism on both the cytosolic and mitochondrial redox states as represented by circulating redox metabolites. The Cys/CySS pair in particular was found to decrease the cytosolic redox state when applied in a reduced redox potential and increased the mitochondrial redox state when applied in an oxidized redox potential. Both the Cys/CySS and the GSH/GSSG couples should be investigated further due to their potential effects on hepatocyte function.en-USThesis/Dissertation