A European Informational Website
learn more
Carnitine, also known as <small>L</small>-carnitine (levocarnitine) is a quaternary ammonium compound synthesized from the amino acids lysine and methionine primarily in the liver and kidneys [1]. It helps in the consumption and disposal of fat in the body because it is responsible for the transport of fatty acids from the cytosol into the mitochondria. It is often sold as a nutritional supplement. Originally found as a growth factor for mealworms and labeled vitamin Bt.
Natural carnitine is the <small>L</small>-stereoisomer. It can be synthesised within the body from the amino acids lysine or methionine. Vitamin C (ascorbic acid) is essential to the synthesis of carnitine. It has been speculated that during growth or pregnancy the requirement of carnitine could exceed its natural production.
Carnitine transports long-chain acyl groups from fatty acids into the mitochondrial matrix so they can be oxidized for energy. Fatty acids must be activated before binding to the carnitine molecule to form acyl-carnitine. The free fatty acid in the cytosol is attached with a thioester bond to coenzyme A (CoA). This reaction is catalyzed by the enzyme fatty acyl-CoA synthetase and driven to completion by inorganic pyrophosphatase.
The acyl group on CoA can now be transferred to carnitine and the resulting acyl-carnitine transported into the mitochondrial matrix. This occurs via a series of similar steps:
Dysfunction of this process leads to the genetic disorders primary carnitine deficiency, carnitine palmitoyltransferase I deficiency, carnitine palmitoyltransferase II deficiency, and carnitine-acylcarnitine translocase deficiency.
It is important to note that carnitine acyltransferase I undergoes allosteric inhibition as a result of malonyl-CoA, an intermediate in fatty acid biosynthesis, in order to prevent futile cycling between beta-oxidation and fatty acid synthesis.
<br/>
<center></center>
The highest concentrations of carnitine are found in red meat and dairy products. Other natural sources of carnitine include nuts and seeds (e.g. pumpkin, sunflower, sesame), legumes or pulses (beans, peas, lentils, peanuts), vegetables (artichokes, asparagus, beet greens, broccoli, brussels sprouts, collard greens, garlic, mustard greens, okra, parsley), fruits (apricots, bananas), cereals (buckwheat, corn, millet, oatmeal, rice bran, rye, whole wheat, wheat bran, wheat germ) and other 'health' foods (bee pollen, brewer's yeast, carob, and kale).
L-Carnitine improved glucose disposal among 15 patients with Type II Diabetes and 20 healthy volunteers.[1] Glucose storage increased between both groups, but glucose oxidation increased only in the diabetic group. Finally, glucose uptake increased about 8% for both.