L-carnitine as essential methylated compound in animal metabolism. An overview

Certain kinds of N-methylated compounds proved to be essential for animals. L-Carnitine is a small-molecular-weight quaternary amine which occurs naturally in micro-organisms, plants and animals. Generally, plants contain little carnitine compared to animals where especially high levels may be found in heart and skeletal muscle. The main function of L-carnitine is the translocation of long-chain fatty acids from the extramitochondrial space to the mitochondrial space. It also facilitates the removal from mitochondria of short-chain and medium-chain fatty acids that accumulate as a result of normal and abnormal metabolism. This pathway provides a means to regenerate the intramitochondrial free coenzyme A under conditions where short-chain acyl-CoA esters are produced at a rate faster than they can be utilized. L-Carnitine is synthetized by most animals but its supplementation can be beneficial under certain condition including insufficient carnitine synthetic enzyme activity, metabolic abnormalities, dietary deficiencies or malnutrition. Several studies on pigs, fish, foal, quail and broiler chickens demonstrate a growth improvement by feeding extra dietary L-carnitine. It has been also found that L-carnitine supplementation resulted in lowered muscle and liver lipid contents. Formaldehyde is involved in metabolism, methylation-demethylation processes of these compounds.