Carbamyl-palmitoyl trans-ferase 1a (CPT1a) and ATP synthase subunit ATP5G1 were strongly down-regulated implying defects in mitochondrial fatty acid transport and ATP synthesis. Electron microscopy showed mitochondrial swelling with abnormalities in shapes and numbers of cristae. Over
the next several weeks improvement of steatosis and apoptosis occurred, with increases in numbers of ALR-expressing cells and ATP levels. However, recovery was transient and was followed at 4-8 weeks by progressive inflammation, hepatocellular necrosis, ductular proliferation and fibrosis, and development of hepatocellular carcinoma by one year. In vitro, depletion of ALR from ALRfloxed/floxed hepatocytes with adeno-Cre infection increased lipid accumulation and decreased R788 cost CPT1a
expression/activity, and caused mitochondrial DNA Ruxolitinib solubility dmso damage, oxidative stress and death of the cells. Hepatic ALR levels were also found to be low in Ob/ Ob and alcohol-treated steatotic mice, and in humans with advanced alcoholic liver disease and nonalcoholic steatohepatitis. CONCLUSIONS: The results indicate that ALR is essential for normal mitochondrial function and lipid homeostasis in the liver. We conclude that the ALR-L-KO mouse provides a novel model to investigate not only mechanisms involved in the development of steatohepatitis but also complications arising from this disorder. Grant support: This work was supported by a VA Merit Review Award (1IO1BX001174) and grants from NIH (PO1AIO81678 and R21AA020846) to CRG. Disclosures: The following people have nothing to disclose: Chandrashekhar R. Gandhi, J. Richard Chaillet, Michael
A. Nalesnik, Sudhir Kumar, Anil Dangi, Robert Ferrell, Tong Wu, Senad Devanovic, Donna B. Stolz, Jiang Wang, Thomas Starzl Lipin family proteins (lipin 1, 2, and 3) act as phosphatidate phosphohydrolase (PAP) enzymes to catalyze diacylglycerol synthesis as the penultimate step in triglyceride synthesis. Though lipin 2 is highly expressed in fed liver, hepatic PAP activity and lipin 1 expression is markedly increased by stimuli that signal increased flux through the triglyceride synthetic pathway. However, the contribution of lipin 1-mediated PAP activity in hepatic fat accumulation in response to fasting or in chronic fatty liver disease is unknown. To examine this point, we developed mice deficient in lipin 1-mediated PAP activity in a liver-specific find more manner by using a Cre-LoxP approach (Alb-Lpin1−/− mice). We evaluated hepatic PAP activity, triglyceride metabolism, liver histology, and hepatic insulin signaling in these mice under fed vs. fasting condition as well as after high fat feeding. All animal studies were approved by the institutional Animal Use and Care Committees of Washington University School of Medicine and fulfilled NIH requirements for humane care. Results: Hepatic PAP activity was reduced by 50% in mice with liver-specific lipin 1 deficiency and this deficit was exaggerated under fasted conditions.