L Carnitine ((R) Carnitine) Co factor for oxidation MedChemExpress Intestinal microbiota metabolism of l carnitine, a nutrient in red meat, promotes atherosclerosis Nature Medicine Carnitine, Choline, Cancer, & Cholesterol: The TMAO Connection Low Bioavailability and High TMAO Production: Novel Insights Into Acetylcarnitine and Carnitine Metabolism KrimsDavis 2025 Molecular Nutrition & Food Research Wiley Online Library Decoding TMAO in the Gut Organ Axis: From Biomarkers and Cell Death Me DDDT Dove Medical Press Characterization of TMAO productivity from carnitine challenge facilitates personalized nutrition and microbiome signatures discovery Microbiome Springer Nature Link