The effect of Lorenzo's oil on oxidative stress in X-linked adrenoleukodystrophy

Abstract 

X-linked adrenoleukodystrophy (X-ALD) is a peroxisomal disorder biochemically characterized by the accumulation of very long chain fatty acids (VLCFA), particularly hexacosanoic acid (C_26:0) and tetracosanoic acid (C_24:0), in tissues and biological fluids. Although patients affected by this disorder predominantly present central and peripheral demyelination as well as adrenal insufficiency, the mechanisms underlying the brain damage in X-ALD are poorly known. The current treatment of X-ALD with glyceroltrioleate (C_18:1)/glyceroltrierucate (C_22:1) (Lorenzo's oil, LO) combined with a VLCFA-poor diet normalizes VLCFA concentrations, but the neurological symptoms persist or even progress in symptomatic patients. Considering that free radical generation is involved in various neurodegenerative disorders and that in a previous study we showed evidence that oxidative stress is probably involved in the pathophysiology of X-ALD symptomatic patients, in the present study we evaluated various oxidative stress parameters, namely thiobarbituric acid reactive species (TBA-RS) and total antioxidant reactivity (TAR) in plasma, as well as the activities of the antioxidant enzymes catalase (CAT), superoxide dismutase (SOD) and glutathione peroxidase (GPx) in erythrocytes from symptomatic and asymptomatic X-ALD patients and verified whether LO treatment and a VLCFA restricted diet could change these parameters. We observed a significant increase of plasma TBA-RS in symptomatic and asymptomatic X-ALD patients, reflecting induction of lipid peroxidation even before the disease was manifested. In addition, LO treatment did not alter this profile. Furthermore, plasma TAR measurement of X-ALD patients was not different from that of controls. Similarly, the antioxidant enzyme activities CAT, SOD and GPx were not altered in erythrocyte from X-ALD patients as compared to controls. We also examined the in vitro effects of hexacosanoic acid (C_26:0) and tetracosanoic acid (C_24:0) alone or combined with oleic (C_18:1)/erucic (C_22:1) acids on various oxidative stress parameters in cerebral cortex of young rats, namely chemiluminescence, TBA-RS, TAR, CAT, SOD and GPx in order to investigate whether those fatty acids were able to induce oxidative stress. We found that there was a significant increase of TBARS and of chemiluminescence in rat cerebral cortex exposed to C_26:0/C_24:0, and that the addition of C_18:1and C_22:1 to the assays did not prevent this effect. Furthermore, TAR measurement was not altered by C_26:0 and C_24:0 acids in rat cerebral cortex. Taken together, our results indicate that lipid peroxidation occurs in X-ALD and that LO treatment does not atenuate or prevent free radical generation in these patients. Therefore, it may be presumed that antioxidants should be considered as an adjuvant therapy for X-ALD patients.

Keywords: Lorenzo's oil, Adrenoleukodystrophy, Glycerol trierucate, Glycerol trioleate, Oxidative stress, Free radicals, Lipid peroxidation