Integrated metagenomics identifies a crucial role for trimethylamine-producing Lachnoclostridium in promoting atherosclerosis

Microbial trimethylamine (TMA)-lyase activity promotes the development of atherosclerosis by generating of TMA, the precursor of TMA N-oxide (TMAO). TMAO is well documented, but same can not be said of TMA-producing bacteria. This work aimed to identify TMA-producing genera in human intestinal microbiota. We retrieved the genomes of human-associated microorganisms from the Human Microbiome Project database comprising 1751 genomes, Unified Human Gastrointestinal Genome collection consisting 4644 gut prokaryotes, recapitulated 4930 species-level genome bins and public gut metagenomic data of 2134 individuals from 11 populations. By sequence searching, 216 TMA-lyase-containing species from 102 genera were found to contain the homologous sequences of cntA/B, yeaW/X, and/or cutC/D. We identified 13 strains from 5 genera with cntA sequences, and 30 strains from 14 genera with cutC showing detectable relative abundance in healthy individuals. Lachnoclostridium (p = 2.9e-05) and Clostridium (p = 5.8e-04), the two most abundant cutC-containing genera, were found to be much higher in atherosclerotic patients compared with healthy persons. Upon incubation with choline (substrate), L. saccharolyticum effectively transformed it to TMA at a rate higher than 98.7% while that for C. sporogenes was 63.8-67.5% as detected by liquid chromatography-triple quadrupole mass spectrometry. In vivo studies further showed that treatment of L. saccharolyticum and choline promoted a significant increase in TMAO level in the serum of ApoE-/- mice with obvious accumulation of aortic plaque in same. This study discloses the significance and efficiency of the gut bacterium L. saccharolyticum in transforming choline to TMA and consequently promoting the development of atherosclerosis.