Phospholipids in X-linked adrenoleukodystrophy white matter: fatty acid abnormalities before the onset of demyelination

Changes in fatty acid composition of complex lipids were analyzed in postmortem white matter from a patient with late onset adrenoleukodystrophy (ALD). The specimen showed three regions with progressive myelin breakdown: morphologically normal white matter; areas with active demyelination and perivascular lymphocyte and macrophage infiltration; and areas with marked gliosis. In the morphologically intact region, cholesterol esters were similar in amount and fatty acid composition to those in control tissue, although marked changes were observed in the actively demyelinating area. Galactolipids in these areas were also similar to those in controls. In contrast, glycerophospholipids were increased in amount and in very long chain fatty acids (VLCFA), which are the hallmark of ALD, at the active edge of the demyelinative lesion and even in the apparently intact sample. Further fractionation of the glycerophospolipids by high performance liquid chromatography showed a significant (up to 39-fold) accumulation of hexacosanoic acid (C26:0) in phosphatidylcholine, but not in other phosphatidyl derivatives. The consistent increases in phosphatidylcholine VLCFA in all samples from the ALD brain, which are postulated to represent progressive stages in the development of the disorder, suggest that phosphatidylcholine may be involved in antigen formation and may underlie an immunological basis for the pathogenesis of ALD.