Abstract 18108: Decreased Fmo3 Expression is Associated With Increased Atherosclerosis and Impaired Liver Function in Apolipoprotein E Null Mice

Abstract

Recent studies demonstrated a strong positive association between blood trimethylamine-N-oxide (TMAO) level and risk for cardiovascular disease. Dietary choline is converted to trimethylamine (TMA) by the gut bacteria, and TMA is then converted to TMAO in the liver, mainly by flavin containing monooxygenase 3 (Fmo3). To examine how FMO3 expression influences atherogenesis, we administered two different FMO3 or control antisense oligonucleotdies (ASOs) to apolipoprotein E (apoE) null mice for 15 weeks. During the last 12 weeks of the ASO treatment, the mice received a chow diet containing 1% choline to enhance TMA production. Hepatic FMO3 mRNA levels were decreased by 80% in mice that received either FMO3 ASO #1 or #2 versus those that received the control ASO. As expected, circulating TMA and TMAO levels were significantly increased and decreased, respectively, in the mice that received the two FMO3 ASOs versus the controls. Other observed changes in the FMO3 ASO-treated mice included: decreased plasma triglyceride, HDL, and glucose levels. Significantly increased VLDL/IDL/LDL cholesterol was observed only in FMO3 ASO #2-treated mice versus the controls. FMO3 ASO treatment increased circulating total bile acid levels by more than 2-fold. Compared to controls, serum markers of hepatic inflammation and necrosis (ALT, AST) were significantly increased in FMO3 ASO treated mice. Histological examination revealed obvious hepatic steatosis and increased inflammatory cell infiltration, suggesting that FMO3 abrogation may be a reasonable model for non-alcoholic steatohepatitis (NASH). We also found a significant increase in quantitative triglyceride and cholesterol content of these livers. Transcriptional profiling by microarrays showed increased hepatic expression of inflammatory genes in mice that received FMO3 ASOs versus the controls. In addition, a significant increase in spleen weight in these mice suggests increased systemic inflammation. Finally, FMO3 knockdown increased atherosclerosis by more than 50% when compared to controls (p < 0.01). This work demonstrates that blocking FMO3 activity has a major impact on liver physiology and atherosclerosis. Our study suggests a protective role for FMO3 in atherosclerosis and liver function.