Carnitine metabolism in hypertensive heart failure Hypertension Research TMAO: how gut microbiota contributes to heart failure Translational Research L carnitine and heart disease Bolton Naturopathic 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 Primary carnitine deficiency cardiomyopathy International Journal of Cardiology