Antioxidant Action of Carnitine: Molecular Mechanisms and Practical Applications

During last decades there has been a growing interest in the potential uses of L-carnitine (LC) as a medicinal agent as well as a nutritional/dietary supplement. In addition to a great interest from medical sciences, carnitine received a substantial attention from pig and poultry industry.The molecular mechanisms accounting for the positive effect of LC on many physiological parameters in farm animals and poultry are not yet fully understood but many protective effects of LC reported in literature, have been postulated to be related to its antioxidant action. However, by the time of writing no comprehensive review on this subject has appeared.Based on the analysis of the recent publications it could be concluded that antioxidant action of carnitine is related to: 1. Its direct scavenging free radicals; 2. Chelating catalytic metals-promoters of reactive oxidative species (ROS), such as Fe and Cu; 3. Maintaining mitochondria integrity in stress conditions and preventing ROS formation; 4. Inhibiting ROS-generating enzymes, such as XO andNAPDH oxidases; 5. Affecting redox-signaling via activation of Nrf2 and PPARα and inhibition of NF-κB with additional synthesis of antioxidant enzymes (SOD, GSH-Px, GR, GST, CAT, etc.) and small antioxidant molecules (GSH); 6. Regulating vitagenes and synthesis of HSPs, sirtuins, thioredoxins and other antioxidant molecules. It seems likely that in biological system in vivo all the aforementioned mechanisms are involved and their interactions provide an important place for carnitine to be a crucial part of the integrated antioxidant systems of the animal and human body. Therefore, carnitine participation in redox signaling and affecting transcription factors (Nrf2, PPARα, NF-κB, etc.) as well as activating the vitagene network are main mechanisms responsible for antioxidant action of LC and its derivatives. Taking into account low carnitine content in grains and poultry and pig diet formulations with limited amounts of animal proteins, carnitine requirement and possible inadequacy in commercial poultry and pig nutrition should receive more attention. Furthermore, protective roles of carnitine in stress conditions of commercial poultry and pig production are difficult to overestimate. Therefore, a development of carnitine-containing antioxidant compositions supplying via drinking water seems to be an important way forward in decreasing the detrimental consequence of various stresses in poultry and pig production.