Effects of dietary choline, betaine, and L‐carnitine on the generation of trimethylamine‐N‐oxide in healthy mice

Trimethylamine-N-oxide (TMAO) is considered to have negative effect on human health. Different precursors of TMAO, such as choline, betaine, and L-carnitine, are commonly found in daily foods. The aim of the present study was to compare the ability of different precursors to be metabolized into TMAO, as well as the possible effect of chronic administration with TMAO precursors on TMAO production. The rate of TMAO generation after single gavage with different precursors was L-carnitine > choline >betaine. Moreover, the serum TMAO level of mice increased more than twofold after administration with choline for 3 weeks compared with L-carnitine and betaine groups, which was accompanied by the change of intestinal flora. After the gavage of choline chloride, the production for TMAO was 2.8 and 1.6 times higher in chronic choline-treated group compared with L-carnitine and betaine groups, respectively. In addition, administration with choline increased the lowest TMAO level after intraperitoneal injection of trimethylamine (TMA) hydrochloride among the three treated groups. These findings indicated that different TMAO precursors had different ability to form TMAO in vivo, and long-term dietary intervention would affect the metabolism of precursors to generate TMA and the TMA oxidation to form TMAO, suggesting that TMAO levels in vivo could be regulated by dietary intervention. PRACTICAL APPLICATION: Diverse TMAO precursors exhibited different ability to be converted into TMAO in vivo. The ability of choline to produce TMAO was stronger than that of betaine and L-carnitine. Long-term dietary intervention would affect the metabolism of precursors to generate TMA and the TMA oxidation to form TMAO, suggesting that TMAO levels in vivo could be regulated by adjustment of dietary structure.