L Carnitine & Arterial Plaque 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 CARNITINE INSUFFICIENCY IS ASSOCIATED WITH ADVERSE OUTCOMES IN PATIENTS WITH HEART FAILURE WITH PRESERVED EJECTION FRACTION JCI l Carnitine in omnivorous diets induces an atherogenic gut microbial pathway in humans