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 BIO INNOVATIONS: Congestive Heart Failure Support TMAO: how gut microbiota contributes to heart failure Translational Research Role of carnitine in disease Nutrition & Metabolism Springer Nature Link L carnitine and heart disease Bolton Naturopathic