Protein and lipid damage in maple syrup urine disease patients: l-carnitine effect

Maple syrup urine disease (MSUD) is an inborn error of metabolism biochemically characterized by elevated levels of the branched chain amino acids (BCAA) leucine, isoleucine, valine and the corresponding branched-chain α-keto acids. This disorder is clinically characterized by ketoacidosis, seizures, coma, psychomotor delay and mental retardation whose pathophysiology is not completely understood. Recent studies have shown that oxidative stress may be involved in neuropathology of MSUD. l-Carnitine (l-Car) plays a central role in the cellular energy metabolism because it transports long-chain fatty acids for oxidation and ATP generation. In recent years many studies have demonstrated the antioxidant role of this compound. In this work, we investigated the effect of BCAA-restricted diet supplemented or not with l-Car on lipid peroxidation and in protein oxidation in MSUD patients. We found a significant increase of malondialdehyde and of carbonyl content in plasma of MSUD patients under BCAA-restricted diet compared to controls. Furthermore, patients under BCAA-restricted diet plus l-Car supplementation presented a marked reduction of malondialdehyde content in relation to controls, reducing the lipid peroxidation. In addition, free l-Car concentrations were negatively correlated with malondialdehyde levels. Our data show that l-Car may have an antioxidant effect, protecting against the lipid peroxidation and this could represent an additional therapeutic approach to the patients affected by MSUD.