Intestinal microbiota metabolism of l carnitine, a nutrient in red meat, promotes atherosclerosis Nature Medicine Trimethylamine Oxide Metabolon Characterization of TMAO productivity from carnitine challenge facilitates personalized nutrition and microbiome signatures discovery Microbiome Springer Nature Link Characterization of TMAO productivity from carnitine challenge facilitates personalized nutrition and microbiome signatures discovery Microbiome Springer Nature Link