We have demonstrated that the intragastric alcohol fed mouse develops hyperhomocysteinemia, ER stress and steatohepatitis. Feeding betaine prevents all of these effects of alcohol. Based upon our previous studies we have developed five specific aims which test the hypothesis that ER stress induced by homocysteine plays a key role in the pathogenesis of alcoholic liver disease:
Aim 1. Determine the effect of liver specific deletion of Grp78 on the susceptibility to liver injury from alcohol or high methionine low folate (HMLF) feeding: this work includes breeding and phenotyping conditional knockout mice, and in vitro and in vivo studies of the effect of deletion of Grp78;
Aim 2. Determine the effectiveness of molecular chaperones in inhibiting alcohol and homocysteine-induced ER stress and steatohepatitis: this work includes in vitro studies as proof of principle and in vivo studies of the protective effect.
Aim 3. Examine the contribution of JNK in ER stress-induced liver injury: these studies will assess the effects of antisense to JNK1, 2, or both in vitro in proof of principle studies and in vivo studies in the alcohol and HMLF models. The first three aims test the hypothesis that ER stress is a major determinant of the severity of alcohol liver disease in the intragastric mouse model.
Aim 4. Determine the mechanism and role of ER stress in hepatic lipid accumulation by testing the hypothesis that alcoholic fatty liver is caused by ER stress induced dysregulation of Insig-1 leading to SREBP activation.
Aim 5. Determine the role of BHMT in alcohol-induced liver injury by testing the hypothesis that the response of BHMT is a critical factor in the development of hyperhomocysteinemia and subsequent downstream activation of ER stress resulting in steatosis and injury;this work will include studies of the species differences (mouse versus rat) in the transcriptional regulation of BHMT, the role of NF-kB in repression of BHMT, the mechanism of induction of BHMT by homocysteine and betaine, and the effect of inhibiting BHMT by feeding CBHcy with alcohol in the rat model to test if the resistance to alcoholic liver disease can be overcome. This work will lead to new approaches to prevent or treat alcoholic liver disease and will expand our knowledge of the causes and effects of ER stress in the liver.
Fatty liver and injury leading to cirrhosis as a consequence of chronic excessive alcohol use is a leading cause of liver-related death and transplantation in the United States. We have identified a link between liver disease and elevated homocysteine levels caused by alcohol in animal models. Therefore, understanding how alcohol increase homocysteine levels and how increased levels of homocysteine contribute to liver damage will open new avenues for preventing and treating liver disease due to alcohol and other causes.
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