Carnitine is a low-molecular-weight compound obtained from the diet that also is biosynthesized from the
essential amino acids lysine and
methionine.
Carnitine has been identified in a variety of mammalian tissues and has an obligate role in the mitochondrial oxidation of long-chain
fatty acids through the action of specialized
acyltransferases. Other roles for
carnitine include buffering of the
acyl coenzyme A (
CoA)-
CoA ratio,
branched-chain amino acid metabolism, removal of excess acyl groups, and peroxisomal
fatty acid oxidation. The growing body of evidence about
carnitine function has led to increased understanding and identification of disorders associated with altered
carnitine metabolism. Disorders of
fatty acid oxidation and metabolism typically are associated with primary and secondary forms of
carnitine deficiency. These disorders, which include increased lipolysis, increased lipid peroxidation, accumulation of acylcarnitines, and altered membrane permeability, have significant consequences for patients with
myocardial diseases and
kidney failure. Therapeutic administration of
carnitine shows promise in treating selected groups of patients who have altered
carnitine homeostasis, resulting in improved cardiac function, increased exercise capacity, reduced
muscle cramps, and reduced intradialytic complications.