Carnitine is an amino acid composite, made up of lysine and methionine. The acetyl group attached to l-carnitine increases the ability to bypass the blood-brain barrier by removing the hydroxyl group and creating a more reactive amino acid.
Acetyl l-carnitine, however, does not increase acetyl co-A concentration within the mitochondria: rather it increases circulating plasma concentration of acetyl co-A around the mitochondria.
Acetyl l-carnitine does increase dopamine output, which in turn increases the release of epinephrine (adrenaline). Epinephrine increases lipolysis (the turning of fat stores into free fatty acids for use as energy) whilst reducing proteolysis (the breakdown of protein into amino acids).
Therefore, increasing available glycerol to be actively transported into available pyruvate increases intra-mitochondria metabolism of acetyl co-A, which then fuels the fire for energy output and production.
Acetyl l-carnitine aids the output of energy without the added intake of glucose, as well as preventing muscle tissue breakdown, thanks to the effects of dopamine and epinephrine.