INTRODUCTION: The liver is the primary organ responsible for the removal of toxic substances from the body by means of a variety of metabolic pathways. One class of proteins responsible for much of the body’s xenobiotic drug and alcohol metabolism is the Cytochrome P450 family of proteins. One protein, Cytochrome P450 Class E Subclass 2 (Cyp2E1), has an integral role in alcohol metabolism by the liver. Cyp2E1 becomes fully activated after an organism has consumed excessive amounts of alcohol excessive alcohol and works with aldehyde dehydrogenase (ALDH) to metabolize ethanol to acetaldehyde. Another metabolic protein, C1q TNF Related Protein 3 (CTRP3), has been shown to effectively prevent alcoholic fatty liver disease (AFLD), specifically with long-term alcohol-induced lipid accumulation. METHODS: In this experiment, 12-week old male mice were fed a Lieber-Decarli alcohol diet (5% ETOH by volume) for 6-weeks. The food intake and body weight of the mice was recorded each day. The mice in the experiment included both wild type and transgenic CTRP3 overexpressing mice. At the end of the 6-week period the mice were euthanized, and the liver was carefully removed, flash-frozen, and prepared for immunoblot analysis of the proteins. RESULTS: Cyp2E1 levels increased significantly in response to ethanol consumption. Cyp2E1 levels were further elevated in ethanol-fed CTRP3 transgenic overexpressing mice. Cyp2E1 levels in CTRP3 transgenic mice were nearly twice that of wild type ethanol-fed mice. CONCLUSIONS: The results of the experiment show a significant increase in Cyp2E1 in mice which overexpress CTRP3. This upregulation of Cyp2E1 with CTRP3 overexpression could explain the mechanism for reduced hepatic lipid accumulation in ethanol-fed CTRP3 transgenic mice.

Alcoholic fatty liver disease (AFLD) is a significant public health concern. Excessive alcohol (ethanol) consumption causes liver cell damage and death, which results in eventual failure of the liver and death. AFLD is the number one cause of liver-related mortality in the United States. Our lab works with the novel protein C1q TNF Related Protein 3 (CTRP3), which inhibits non-alcoholic fatty liver disease, however the effects on AFLD are unknown. Therefore, the purpose of this experiment is to determine if CTRP3 prevents ethanol-induced liver cell death. The H4IIE rat hepatoma cell line was chosen for experimentation as a cell culture model of liver tissue. To determine a suitable alcohol level H4IIE cells were treated with 50, 100, and 200 mmol of ethanol for 18-24 hours. Trypan Blue was used to identify the dead/damaged cells, as only dead/damaged cells will be stained blue with this protocol. We observed that 100 mmol of ethanol consistently induced ~10% mortality rate in these cells. Next, we tested the ability of CTRP3 to reduce ethanol-induced mortality. We added purified CTRP3 protein to the cell media along with the 100 mmol ethanol treatment. The addition of CTRP3 reduced the amount of alcohol-induced cell death/damage in the H4IIE cell line by approximately 60%. Our next goal was to determine how CTRP3 reduces ethanol-induced death. The Akt signaling pathway is a well-known inhibitor of cell death. Therefore, to determine if CTRP3 attenuated ethanol-induced cell damage/death through activation of the Akt signaling pathway, another set of cells was treated with 100 mmol of ethanol and CTRP3 (with or without insulin). Western blots were used to compare the amount of active Akt (phosphorylated) in the CTRP3-treated and non-treated cells. A Western blot utilizes an electric current to separate denatured protein samples on a SDS-page gel, separating the proteins based on size. The smaller the protein the faster it migrates across the gel. The proteins are then transferred to a membrane for analysis, through exposure to commercial antigens and chemiluminescence imaging. There was no change in the amount of total or active Akt between the samples treated with or without CTRP3. We conclude that CTRP3 protects liver cells from ethanol-induced damage/death, but not through activation of the Akt pathway.

Abstract available through The FASEB Journal.