plays a critical role in transporting fats into the powerhouse of the cells where they are burned for energy. Some experts have argued that carnitine may have a rate limiting effect on fat oxidation. Therefore
has been promoted as a method to increase fat burning. However, it is somewhat difficult to increase muscle carnitine by supplementation. These researchers, who were also involved in creatine studies that documented muscle uptake of
with supplementation, decided to test factors that might contribute to carnitine uptake into muscle. They hypothesized that insulin might augment muscle carnitine accumulation. Their experiments indeed showed that when carnitine and insulin were both elevated in the blood there was an acute accumulation of carnitine in muscle by 12%. This is the first study to demonstrate a method to augment carnitine uptake into skeletal muscle. The findings are encouraging because it provides evidence that the muscle carnitine pool is capable of being enlarged, which should have significant effects on
Stephens FB, Constantin-Teodosiu D, Laithwaite D, Simpson EJ, Greenhaff PL. Insulin stimulates L-carnitine accumulation in human skeletal muscle. FASEB J. 2006 Feb;20(2):377-9. Epub 2005 Dec 20.