Metabolic studies of adrenoleukodystrophy.

Two series of metabolic studies were prompted by the previous finding that the brain and adrenal tissues of patients with adrenoleukodystrophy, an X-linked genetic disorder, contain unusually long-chain (C22--C32) fatty acids in cholesterol esters and gangliosides. Postmortem brain tissues from three patients were assayed for activities of the three distinct cholesterol ester hydrolases, using [4-14C]cholesterol oleate, lignocerate and cerotate as the substrates. No deficiency of the crude mitochrondrial (pH 4.2), the microsomal (pH 6.0), or the myelin-localized cholesterol ester hydrolases was detected, although the activities of the myelin-localized cholesterol ester hydrolase against cholesteryl lignocerate and cerotate were too low for reliable assays. The activities of the microsomal and myelin-localized hydrolases were actually higher in adrenoleukodystrophy than in controls. Uptake and exclusion by cultured fibroblasts of [1-14C]stearic, [1-14C]lignoceric and [1-14C)cerotic acids were also examined. All fatty acids were avidly taken up by the fibroblasts. Stearic acid was excluded from the cells much more rapidly than lignoceric or cerotic acid. No difference was observed in the uptake and exclusion of fatty acids between the controls and adrenoleukodystrophy, except that cells from some cases of adrenoleukodystrophy consistently took up the very long chain fatty acids at greater rates than the control cells. Neither did the distribution of the label among individual lipids reveal differences between the controls and adrenoleukodystrophy, although there were interesting and dramatic differences in the metabolism of lignoceric acid and cerotic acid. Cerotic acid appeared largely inert with 90--95% remaining intact over eight days, while lignoceric acid was mostly incorporated into complex lipids. This series of studies did not uncover the fundamental genetic defect underlying adrenoleukodystrophy.