Carnitine
Carnitine is a water-soluble vitamin like compound that the body utilizes to turn fat into energy. Carnitine works as part of an enzymatic complex formed from carnitine acyltransferase 1, carnitine translocase and carnitine transferase 11. Carnitine is a chiral molecule by virtue of the fact that it possesses an asymmetric carbon atom. C-3, which bears as substituents a hydrogen, a hydroxy group, a trimethylamino methyl group, and a carboxymethyl group. Carnitine has an important function in beta-oxidation of fatty acids in every organ of a living body. Cells in every organ produce ATP (adenosine triphosphate), which is the energy source for the cells, in mitochondria owing to the beta-oxidation of fatty acids. An acyl group of the fatty acids is transported in the mitochondria through a carnitine action to be transformed into acyl CoA, and then the acyl CoA is beta-oxidized to generate ATP. Carnitine contains an asymmetry centre and can therefore exist in the form of two enantiomers, designated R-(-)-carnitine and S-(+)-carnitine, respectively. Of these, only R-(-)-carnitine is present in living organisms where it acts as a carrier for the transport of fatty acids across the mitochondrial membranes. Carnitine contain a single centre of asymmetry and therefore may exist as two enantiomers, designated D(+)-carnitine and L(-)carnitine-and, obviously in form of racemate. Of these only L(-)-carnitine is found in living organism, were it functions as a vehicle for transporting fatty acids across mitochondrial membranes. L-carnitine may be in form of inner salt or in form of pharmacologically acceptable salt. D-carnitine is a competitive inhibitor of carnitine-linked enzymes such as carnitine acetyl transferase (CAT) and carnitine palmitoyl transferase (CPT) and that D-carnitine can deplete the L-carnitine level of myocardium and skeletal muscle. Consequently, it is essential that L-carnitine exclusively be administered to patients under medical treatment for heart diseases or regular haemodialytic treatment or lowering of blood lipids, particularly in long term treatments. Carnitine is a naturally occurring substance in the human body required for energy metabolism at the cellular level. It has been shown to have a role in transporting fatty acids into mitochondria to help produce energy and in removing toxic waste from the cells. Carnitine's essential role is to transport fatty acids of 12-18 carbons across the outer and inner membranes of the mitochondria. Carnitine palmitoyltransferase catalyzes the transfer of the fatty acid or acyl group to camitine at the outer surface of the mitochondrial membrane. The acylcarnitine then goes across the outer membrane of the inner surface of the mitochondrial membrane. L-carnitine (3-hypodroxy-4-N-trimethylaminobutyric acid) has two main functions, both critical to energy metabolism. The first is translocation of long-chain fatty acids from the cytosol across the outer and inner mitochondrial membranes and intervening space into the mitochondrial matrix. The second function is to modulate intracellular CoA homeostasis within the mitochondrial matrix by transesterifation of acyl-CoA esters produced in B-oxidation which regenerates CoA and acylcarnitine. L-carnitine and particularly propionyl L-carnitine or acetyl L-carnitine can act by varying the lipid substrate from which the various vasoconstrictor and aggregation-promoting factors derive as a result of the effects of cyclo-oxygenase and lipo-oxygenase, by reducing their formation and by promoting the synthesis of antiaggregant and vasodilators factors. L-carnitine plays an important role in metabolism, especially in transporting long-chain fatty acids through the inner mitochondrial membrane. L-carnitine is significant as a supplemental nutrient and also promotes, as an additive to fermentation media, the growth of yeasts and bacteria. There are many pathological states the underlying cause of which is a deficiency of L-carnitine, and L-carnitine determination is necessary in order to establish the precise a etiology of the related disease processes. Therapeutical uses of L-carnitine inner salt have long since been known. L-carnitine has been used in the cardiovascular field for the treatment of acute and chronic myocardial ischaemia, angina pectoris, heart failure and cardiac arrhythmias. Carnitine's importance in cardiac metabolism and function has been emphasized by a number of studies showing a close association between systemic and myopathic carnitine deficiency and both hypertrophic and congestive cardiomyopathies. Reports indicate L-Carnitine therapy converts abnormal fatty acid metabolism to normal, increases the concentration of L-Carnitine in cardiac muscle and in blood, and improves cardiac output and blood pressure. In the nephrological field, L-carnitine has been administered to chronic uraemic patients undergoing regular haemodialytic treatment to combat myasthenia and the onset of muscular cramps. The use of L-carnitine in association with an anti-oxidant and in particular with thioctic acid is particularly advantageous as it allows an increase in cellular metabolism to be obtained without incurring a concomitant increase in the production of reactive oxygen species. L-carnitine has increasingly established itself on the so-called health food, medical food or nutraceutical market.
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