Trimethylamine N-oxide ameliorates hepatic damage including reduction of hepatic bile acids and cholesterol in Fxr-null mice

There are conflicting animal experiments on the effect of trimethylamine N-oxide (TMAO), the dietary metabolite, on non-alcoholic fatty liver disease (NAFLD). This study aims to determine the effect of TMAO on NAFLD. A diet containing 0.3% TMAO was fed to farnesoid X receptor (Fxr)-null mice, a model of NAFLD, for 13 weeks. Fxr-null mice fed TMAO showed significant reductions in liver damage markers but not wild-type mice. Hepatic bile acid and cholesterol levels were significantly decreased, and triacylglycerol levels tended to decrease in TMAO-fed Fxr-null mice. Changes in mRNA levels of hepatic bile acid and cholesterol transporters and synthetic enzymes were observed, which could explain the decreased hepatic bile acid and cholesterol levels in Fxr-null mice given the TMAO diet but not in the wild-type mice. These results suggest that TMAO intake ameliorates liver damage in Fxr-null mice, further altering bile acid/cholesterol metabolism in an FXR-independent manner.