Alterations of phospholipid metabolites in postmortem brain from patients with Alzheimer's disease.

To test the hypothesis that brain cell membranes degenerate in Alzheimer's disease (AD), we measured the levels of phospholipids, their water-soluble metabolites, and glycerophosphocholine (GPC) cholinephosphodiesterase activity in postmortem brain tissue from patients with AD and age-matched controls. We found significantly higher levels of the phospholipid catabolite GPC in AD brain. In contrast, choline and ethanolamine levels were significantly lower in AD, and phospholipid levels were slightly decreased. Furthermore, in AD the activity of the GPC-degrading enzyme GPC cholinephosphodiesterase was unaltered. Our results indicate that membrane phospholipid catabolism is increased in AD brain. Inasmuch as the tissue levels of initial phospholipid precursors were decreased, we suggest that phospholipid turnover is elevated in this neurodegenerative disease.