In vivo imaging to evaluate the effect of PUFAs on alcoholic fatty liver disease

Johns Hopkins University, Baltimore MD

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Abstract

DESCRIPTION (provided by applicant): Cirrhosis is characterized by advanced steatosis, fibrosis, and inflammation of the liver that often leads to liver failure, can progress to hepatocellular carcinoma, and is the twelfth leading cause of death in the United States. Alcoholic cirrhosis is thought to develop through repeated activation of the acute hepatic injury response: ethanol or another stressor activates Kupffer cells (liver-specific macrophages), which signal hepatic stellate cells to proliferate and overproduce extracellular matrix, eventually leading to fibrosis. Although the role of alcohol overconsumption alone in determining the long-term progression of liver disease has been studied extensively, the acute hepatic injury response to alcohol and how it is influenced by fat stored in hepatocytes and consumed in the diet is not well understood. Lipotoxicity, in which lipids stored in non-adipose tissues promote cell dysfunction and death, has been documented in multiple human organ systems and tissues, but is not well characterized in the liver. I hypothesize that dietary polyunsaturated fatty acids (PUFAs), already know to protect against lipotoxicity-induced cell death in the heart when compared with dietary saturated fatty acids and to attenuate inflammation by suppressing signaling through the TLR4 receptor, will protect against steatohepatitis by mitigating the inflammatory effects of alcohol. Larval zebrafish will serve as a model for investigation of how the presence of alcohol affects the metabolism of dietary lipids, and the role of diet composition in alcoholic liver injury. To this end I have optimized an ethanol treatment procedure that results in a significant increase in hepatic lipid content without affecting feeding behavior. I have also developed HPLC methods that will be used to analyze whole-body triglyceride and phospholipid composition of zebrafish larvae treated with ethanol and given a range of diets with varying fatty acid content. Liver injury will be assayed using qRT-PCR and in situ hybridization for inflammatory cytokines, immunostaining for fibrosis, and live imaging of the cell populations involved in the hepatic injury response in several fluorescent transgenic zebrafish lines.