Role of brain acetaldehyde in drinking preference: genetic modification of alcohol oxidizing enzymes catalase and CYP2E1 in C57BL/6 mice and their characterization, The

Abstract

EtOH-derived acetaldehyde is believed to influence alcohol drinking preference behavior as evidence in literature shows acetaldehyde in the central nervous system can increase alcohol consumption as measured by conditional place preference and increases dopamine release. The work presented in this dissertation evaluates the behavioral effects of acetaldehyde through the use of genetically modified mouse models lacking the enzymes (catalase and Cyp2e1) that are primarily responsible for acetaldehyde formation in the brain. Through animal husbandry, double knockout mice deficient in both catalase and Cyp2e1 were also generated. Absence of these enzymes should theoretically nearly eliminate (80% reduction) acetaldehyde production within the central nervous system, with catalase and Cyp2e1 contributing 60% and 20% of EtOH to AcH metabolism, respectively. To confirm this assumption, a method for quantifying very low concentrations of EtOH and acetaldehyde (limit of detection (LOD) of 100 nM) was developed using headspace gas chromatography mass spectrometry and diligent sample preparation. The Cyp2e1-/-, Cat-/- and DKO mice were subjected to a two bottle choice experiment to examine drinking preference and consumption compared to wild-type (WT) counterparts. A lack of catalase caused decreased drinking consumption in both sexes. By contrast, Cyp2e1 absence had no effect on alcohol drinking. A gender difference was noted in DKO mice such that females, but not males, exhibited decreased drinking preference and consumption. Characterization of these animals revealed that mice lacking Cyp2e1 (Cyp2e1-/-) were underweight and required supplemental moist chow prior to weaning. Mice lacking catalase (Cat-/-) were overweight and had visceral and intra-organ lipid accumulation. Further analysis of the Cat-/- mice showed oxidative stress, metabolic dysfunction and glucose intolerance, and pathological changes in lipid trafficking. Mice lacking both catalase and Cyp2e1 (DKO) were slightly overweight and a small percentage exhibited eye and teeth developmental abnormalities. The data herein establish a sensitive method to analyze and correlate the concentration of acetaldehyde in the future as well as a behavioral role in drinking preference as the lack of acetaldehyde in the CNS, due to the lack of acetaldehyde producing enzymes, decreases drinking preference in female catalase-null and Cat/Cyp2e1-null mice, but only in catalase-null males. This also indicates a sex-dependent mechanism through which acetaldehyde is having an effect. In addition, these provide preliminary evidence toward the role of catalase on lipid changes and metabolic dysfunction and a prediabetic phenotype. Finally, data presented in the following chapters indicate distinct differences exist between males and females in relation to voluntary EtOH consumption and lipid alterations.