Epigallocatechin gallate inhibits high-fat/choline diet-induced trimethylamine production via regulation of intestinal Serratia and Lactobacillus communities.

High-fat/choline diets can induce the production of the enterogenous metabolite trimethylamine-N-oxide (TMAO). TMAO is synthesized from its precursor trimethylamine (TMA), which is generated via choline cleavage catalyzed by choline trimethylamine-lyase/choline TMA-lyase-activating enzyme (CutC/D) expressed by gut microbes; subsequently, TMA is oxidized to TMAO by flavin-containing monooxygenase 3 (FMO3) in the liver. While epigallocatechin gallate (EGCG) is well recognized for its gut microbiota-remodeling capacity, how it modulates TMA/TMAO metabolism through this pathway, along with the time-dependent effectiveness of EGCG intervention, remains to be elucidated. We conducted animal experiments to evaluate the inhibitory effect of time-dependent EGCG intervention on TMA/TMAO production induced by high-fat/choline diets in mice. We further identified gut bacterial strains associated with TMA levels using metagenomics and machine learning techniques, and verified the underlying mechanisms through in vitro anaerobic culture and molecular simulations. Results demonstrated EGCG significantly reduced TMA/TMAO levels in mice by regulating the choline-CutC/D-FMO3 axis. Specifically, Serratia exhibited a positive correlation with CutC enzyme activity, while Lactobacillus showed a negative correlation with TMA levels. Mechanistically, EGCG exerted a direct bacteriostatic effect on Serratia marcescens by disrupting its cell membrane structure and inhibiting its CutC enzyme activity. Meanwhile, EGCG significantly enriched Lactobacillus johnsonii, with the abundance of this strain peaking after long-term intervention. Although Lactobacillus johnsonii does not directly degrade TMA, it indirectly reduces TMA levels by inhibiting the growth of Serratia marcescens. Long-term continuous supplementation with EGCG yielded the optimal inhibitory effect on TMA/TMAO production. Hence, EGCG exerts its function primarily through a dual mechanism: directly inhibiting the growth and CutC enzyme activity of the TMA-producing bacterium Serratia marcescens, and indirectly antagonizing Serratia marcescens by promoting the proliferation of the beneficial bacterium Lactobacillus johnsonii. This study provides novel theoretical insights into the mechanism by which EGCG alleviates TMA/TMAO metabolic disorders induced by high-fat/choline diets via gut microbiota modulation.