The objective of this study was to test whether macromolecule oxidative damage and altered enzymatic antioxidative defenses occur in patients with
medium-chain acyl coenzyme A dehydrogenase (
MCAD) deficiency. We performed a cross-sectional observational study of in vivo parameters of
lipid and
protein oxidative damage and
antioxidant defenses in asymptomatic, nonstressed, MCAD-deficient patients and healthy controls. Patients were subdivided into three groups based on
therapy: patients without prescribed supplementation, patients with
carnitine supplementation, and patients with
carnitine plus
riboflavin supplementation. Compared with healthy controls, nonsupplemented MCAD-deficient patients and patients receiving
carnitine supplementation displayed decreased plasma sulfhydryl content (indicating
protein oxidative damage). Increased erythrocyte
superoxide dismutase (SOD) activity in patients receiving
carnitine supplementation probably reflects a compensatory mechanism for scavenging reactive species formation. The combination of
carnitine plus
riboflavin was not associated with oxidative damage. These are the first indications that MCAD-deficient patients experience
protein oxidative damage and that combined supplementation of
carnitine and
riboflavin may prevent these biochemical alterations. Results suggest involvement of
free radicals in the pathophysiology of
MCAD deficiency. The underlying mechanisms behind the increased SOD activity upon
carnitine supplementation need to be determined. Further studies are necessary to determine the clinical relevance of oxidative stress, including the possibility of
antioxidant therapy.