Identification of choline-degrading bacteria from healthy human feces and used for screening of trimethylamine (TMA)-lyase inhibitors

Abstract

Gut microbiota-based choline metabolism produces trimethylamine (TMA), which is then further converted to the atherosclerosis-promoting metabolite trimethylamine-N-oxide (TMAO) by hepatic flavin-containing monooxygenases (FMOs) and TMAO plays an essential role in cardiovascular disease (CVD). Many Chinese herbal medicines had been used for the treatment of CVD. This study aimed to screen choline-degrading bacteria from healthy human feces and establish a platform in silico and in vitro approaches for screening TMA-lyase inhibitors from Chinese herbal medicines. Choline-degrading bacteria were screened from healthy human feces in basic salt medium using culture method. The isolated strains were identified as Klebsiella pneumoniae based on 16S rRNA and the presence of CutC gene. Structure of CutC choline lyase was obtained from the RCSB Protein Data Bank database, and the modeled structure was docked with natural compounds of Chinese herbal medicines origin using MOE. Further, we investigated the inhibitory effects of selected compounds by picric acid-toluene method using K. pneumoniae as bioassay indicator. We found that TMA level was significantly decreased when treated with β-sitosterol and resveratrol. This study initially demonstrates the inhibitory effect of β-sitosterol and resveratrol on the gut microbiota responsible for choline metabolism to TMA and sets up an inhibitor-screening platform for further experiments. It can be used as a model to evaluate herbal drug sources and their effects on the gut microbiota for cardiovascular disease.

Keywords: Choline; Gut microbiota; Inhibitor; Klebsiella pneumoniae; Trimethylamine.