Frontiers The gut microbial metabolite trimethylamine N oxide and cardiovascular diseases Identification of TMAO producer phenotype and hostdietgut dysbiosis by carnitine challenge test in human and germ free mice Gut Simultaneous quantification of trimethylamine oxide and its precursors from gut microbial metabolic pathway Trimethylamine N Oxide, More Red Meat for the Vascular Scientists Hypertension