handdator

Visa fullständig version : L-Karnitin vs Acetyl-L-Karnitin och fungerar dem?


Barbastark
2011-10-09, 19:31
Hejhej

Det jag undrar är dels vad skillnaden är mellan de två samt om dem har någon bevisad effekt?

Mycket glad om någon kan komma med nått bra info

MVH

Eddie Vedder
2011-10-09, 19:49
Det var uppe ganska nyligen. Men hursomhelst saknar L-karnitin all form av evidens för ökad fettförbränning hos tränande så vitt jag vet. Men det ska kanske inte uteslutas.

Abstract

Carnitine plays a central role in fatty acid (FA) metabolism. It transports long-chain fatty acids into mitochondria for beta-oxidation. Carnitine also modulates the metabolism of coenzyme-A (CoA). It is not surprising that the use of supplementary carnitine to improve physical performance has become widespread in recent years, although there is no unequivocal support to this practice. However, critical reflections and current scientific-based knowledge are important because the implications of reduced or increased carnitine concentrations in vivo are not thoroughly understood. Several rationales have been forwarded in support of the potential ergogenic effects of oral carnitine supplementation. However, the following arguments derived from established scientific observations may be forwarded: (i) carnitine supplementation neither enhances FA oxidation in vivo or spares glycogen or postpones fatigue during exercise. Carnitine supplementation does not unequivocally improve performance of athletes; (ii) carnitine supplementation does not reduce body fat or help to lose weight; (iii) in vivo pyruvate dehydrogenase complex (PDC) is fully active already after a few seconds of intense exercise. Carnitine supplementation induces no further activation of PDC in vivo; (iv) despite an increased acetyl-CoA/free CoA ratio, PDC is not depressed during exercise in vivo and therefore supplementary carnitine has no effect on lactate accumulation; (v) carnitine supplementation per se does not affect the maximal oxygen uptake (VO2max); (vi) during exercise there is a redistribution of free carnitine and acylcarnitines in the muscle but there is no loss of total carnitine. Athletes are not at risk for carnitine deficiency and do not have an increased need for carnitine. Although there are some theoretical points favouring potential ergogenic effects of carnitine supplementation, there is currently no scientific basis for healthy individuals or athletes to use carnitine supplementation to improve exercise performance.

Heinonen OJ. Carnitine and physical exercise. Sports Med. 1996 Aug;22(2):109-32.

Abstract

Carnitine is an endogenous compound with well-established roles in intermediary metabolism. An obligate for optimal mitochondrial fatty acid oxidation, it is a critical source of energy and also protects the cell from acyl-CoA accretion through the generation of acylcarnitines. Carnitine homeostasis is affected by exercise in a well-defined manner because of the interaction of the carnitine-acylcarnitine pool with key metabolic pathways. Carnitine supplementation has been hypothesized to improve exercise performance in healthy humans through various mechanisms, including enhanced muscle fatty acid oxidation, altered glucose homeostasis, enhanced acylcarnitine production, modification of training responses, and altered muscle fatigue resistance. Available experimental clinical studies designed to assess the effect of carnitine on exercise metabolism or performance in healthy humans do not permit definitive conclusions to be drawn. In the aggregate, however, these studies suggest that carnitine supplementation does not improve maximal oxygen uptake or metabolic status during exercise in healthy humans. Carnitine administration for </=1 mo in humans increases plasma carnitine concentrations but does not increase muscle carnitine content. Additional clinical trials integrating physiologic, biochemical, and pharmacologic assessments are needed to definitively clarify any effects of carnitine on exercise performance in healthy persons.

Brass EP. Supplemental carnitine and exercise. Am J Clin Nutr. 2000 Aug;72(2 Suppl):618S-23S.

exevision
2011-10-09, 20:02
http://www.kolozzeum.com/forum/showthread.php?t=172677

Barbastark
2011-10-09, 20:28
Ok tackar!

Men så vad är skillnaden mellan L-karnitin och Acetyl-L-Karnitin?

Eddie Vedder
2011-10-09, 20:36
http://en.wikipedia.org/wiki/Acetylcarnitine

http://en.wikipedia.org/wiki/Carnitine

Barbastark
2011-10-10, 08:17
http://en.wikipedia.org/wiki/Acetylcarnitine

http://en.wikipedia.org/wiki/Carnitine

Så i acetyl-l-carnitin så har dem ändrat något för att öka biotillgängligheten?