Intestinal microbiota metabolism of l carnitine, a nutrient in red meat, promotes atherosclerosis Nature Medicine L Carnitine intake and high trimethylamine N oxide plasma levels correlate with low aortic lesions in ApoE transgenic mice expressing CETP ScienceDirect L Carnitine Male Enhancement: What the Evidence Shows for Energy, Sperm Health, and Performance Characterization of TMAO productivity from carnitine challenge facilitates personalized nutrition and microbiome signatures discovery Microbiome Springer Nature Link