The Carnitine butyrobetaine trimethylamine N oxide pathway and its association with cardiovascular mortality in patients with carotid atherosclerosis Atherosclerosis Hong Kong Journal of Paediatrics [HK J Paediatr (New Series) 2020;25:23 29] 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 Serum L Carnitine Levels Are Associated With First Stroke in Chinese Adults With Hypertension Stroke