Revisiting the Role of Carnitine in Heart Disease Through the Lens of the Gut Microbiota L carnitine is primarily synthesized in the liver from the amino acids lysine and methionine through a series of four enzymatic reactions, with the liver and kidneys converting the precursor butyrobetaine into active JCI l Carnitine in omnivorous diets induces an atherogenic gut microbial pathway in humans Role of carnitine in disease Nutrition & Metabolism Springer Nature Link Safety and efficacy of L carnitine supplementation in improving cardiac function of hemodialysis patients: a systematic review and meta analysis International Urology and Nephrology Springer Nature Link