Update on critical evidence for use of carnitine analogs in clinical practice in CNS disorders

L-carnitine (LC) is part of the carnitine shuttle system at the mitochondrial inner membrane (MIM) and transports long chain fatty acids over the MIM route. Acetyl-L-carnitine (ALC), the acetyl ester of LC, plays an essential role in intermediary metabolism. To ALC are ascribed neurotrophic actions, antioxidant and antiapoptotic activity, positive effects on mitochondrial metabolism, and stabilization of intracellular membranes. Acylcarnitine and LC supplementation have shown beneficial effects in the treatment of aging, chronic degenerative pathologies and the slowing of the progression of mental deterioration in neurodegenerative diseases, and painful neuropathies. ALC is reported to affect brain energy and phospholipid metabolism and to interact with cell membranes, proteins, and enzymes. It also shows a neuromodulatory effect on synaptic morphology and neurotransmitter synaptic transmission, including that of acetylcholine and dopamine. All these data suggest that ALC can affect several targets in the central nervous system. The roles and effects of LC and ALC have led researchers to investigate carnitine’s involvement in a variety of neuropathological states and treatments, including autism, Parkinson’s disease, Alzheimer’s disease, Down’s syndrome, Huntington’s disease, cerebellar ataxia, age-associated mental decline, hepatic encephalopathy, and ammonia neurotoxicity. This review summarizes evidence that carnitine analogs play many roles in serious neurological pathologies.